Anyone who has wanted true duals on 3rd Gens have always had to deal w/ clearance problems and such. I myself have had a dual 2.5" exhaust, back to single 3", and then back to a 3" dual set-up, but with my new engine I bought full length headers, and hadn't had any exhaust ran. So instead of trying to figure a new inventive way of running a low hanging dual exhaust set-up, i tried a Vortex Cone muffler insert. It is a cone (see pic below) that goes directly into the collector with no need for any pipes. I installed them this weekend and they sound awesome. I can feel no noticable power differance at all. They are mmuch quieter than I thought they'd be, but they are designed for late-model dirt cars where certain tracks mandate a muffler rule. They are much quieter than the 3" Dynomax Race Bullets my brother has on his truck. The bought from Afco Racing and they're $59.99, about the same a Flowmaster 2 chamber. Before a flamewar gets started, I know a lot of ppl where emmisions tests are mandated can't use them and so forth, but for a limited use street car thats sees mostly strip duty they someone doesn't want to run just open headers they are a great alternative.


---------------------------------------------

***PRODUCT INFO****
PRODUCT: 72-32520
Vortex Cone 3in. - Stainless Steel
Sound Insurance!!


100% T-304 Stainless Steel Construction
Compact Size Fits All Racing Applications
Ultra Lightweight-Less Than 1/2 lb. each
Little or No Power Loss
Easy Bolt Installation
Insert Cones on 3", 3 1/2", 4", 4 1/2", 5"
Turn Down with Insert Cone in 3", 3 1/2", 4"
How It Works: The Vortex Insert Cone, installed near the exit of the header collector or muffler outlet, provides a large friction area to reflect and dissipate sound energy, thus reducing the dB level. The open area of the cone is actually greater than the area of the collector or exhaust pipe, thus reducing a backpressure condition. Because no significant backpressure has been introduced, the engine is still able to use the scavenge ability of a good header to creat horsepower and torque. Dyno and track testing show significant noise reduction with little or no power loss.



Vortex Cone Mufflers
72-32510 Vortex Cone 3 1/2 in.- Stainless Steel $59.95
72-32520 Vortex Cone 3in. - Stainless Steel $59.95
72-32530 Vortex Cone 4in. - Stainless Steel $59.95
72-32540 4.5 in. VORTEX CONE ASSEMBLY $59.95
72-32550 5.0 in. VORTEX CONE-SLOTTED $59.95





------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing



[This message has been edited by Basett_Racing (edited June 13, 2001).]

 

Ok, let's block exhaust flow where it matters most(in the center of the exhaust stream near the exit of the collector), lets reflect some of the hot center gases towards the walls, lets create lots of turbulence upstream and downstream of the collector exits and lets push gases back into the collector. then we'll tell people it quiets your exhaust and hardly hurts your power output. Why not save some money and just stuff steel wool in the collectors. Effect should be the same. Betcha this one'll be a big hit with the same folks who bought into that "Tornado" crap.

As always - show me the dyno sheet!

[This message has been edited by 88IROCs (edited June 19, 2001).]

 

Yeah, you're right. Let's stuff it all into a single pipe that snakes around under the car and comes all the way out the back. Or if that doesn't suit you, let bend, kink and shoehorn a 3" exhaust under the car that not only looks terrible, but makes for some SUPER GROOVY sparks when they bottom out on the pavement - yeah you're on top of it. Say, have you ever heard of the Hava-A-Tampa Late Model Dirt Car Series?? How 'bout the Southern All-Stars Series or Rick's Super Late Model Series?? Probably Not huh?? Because if you had, you may realize that this is one of the most popular mufflers that is run in those series. The other is the LoBack muffler which, as we covered earlier, we just don't have enough room under our cars. Now, let's be clear on this. A lot of these guys do this for a living, and they do not run a cheap, backyard budget. They run $18-20K chassis(usually at least two cars), $35-40K engines, many have 18 wheelers w/ huge enclosed trailors and employ several people. They can afford any kind of muffler thay want, and can run any muffler that will pass the Db level test(which varies from track to track). They are not running Flowmasters, Dynomax, or any other popular street muffler, which are quieter by the way, They are running the Cones and the Lobacks. My boss actually owns one of these cars(He owns a multimillion $ CNC machine shop, so he can afford it) and he runs the Cones. You say you want to see dyno tests, well I don't have that, but I can tell you that he raced at a track that he normally doesn't race at that requires mufflers last Fri. Night then the following Sat, He raced at the the track he always raced at w/o taking off the mufflers, and his normal lap times were no slower that they been being. I will also post my times, when I go back to the track, as well. If its slower I will tell you how much. I do expect some loss, as I would with ANY muffler.

But laying all the sarcasm to the side, these are a proven and widely used muffler. The engine that is in my boss's car right now dyno'd at 748HP, and his car really showed little or no power loss with the Cones. Maybe it boosted TQ enough out of the corner to make for a little loss at the end of the straightaway. And in my case, I really don't care how much power it kills, because now I can drive the car on the street w/o worrying about it dragging on everything, I don't have to look at a huge monsterous looking bent up exhaust hanging 1 1/2 from the ground, it sounds good, and at the track, I can take them off with 3 small bolts each.

------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

i've had true duals in the past and never had a clearance issue. about to get them again. my shop just runs the pipes side by side in the stock location.

 

Get off your high horse about purpose-built tube-framed race cars with hand-built exhausts and tell me how this relates to the majority of third-genners with daily driven street cars(i.e,... something that can deal with speed-bumps and potholes). Your preaching may be better used at Dirt_Cars_R_Us.org, but I fail to see the usefullness of these things for even a car that sees "limited street use".

I went to a lot of trouble to hand-fab(with help from friends) a custom 3.5" exhaust for my daily driven(approx. 20 000 miles/year) IROC, and I'll be darned if I will plug it up with a 'gimmick' that makes ludicrous(and unsubstantiated) claims. Btw, my ground clearance is no worse than with the factory exhaust.

I'd guess your '82 doesn't have any ground clearance issues(judging by the pics on your webpage), so you could run any exhaust set-up you want. But for those of us whose Camaro won't be mistaken for a 4x4, duals present less than ideal clearance.

Finally, you mentioned you put these cones in your collectors. The smallest size they come in is 3"(as far as I could tell). Are you running 3" collectors. And are you saying that disturbing the flow inside the collectors and at the collector exits caused you "no noticeable power difference at all"?

 

88IROCs,
Once again, you have shown us all that you either haven't READ my posts, or that you can't UNDERSTAND them. You act as though I am trying to sell these things or something. What's your deal?? You have clearly stated that you have a custom 3.5" exhaust that you are run on your daily driven street car. I am assuming that you mean its a single system, since 3.5" duals would be, uh, how would you word it, "ludicrous",for a daily driven car. If this is the case, then I wasn't talking to you in my original post in the first place. I didn't say daily driven, go get groceries, and pick the kids car, I said ALTERNATIVE to full exhaust on high HP street/strip cars. ALTERNATIVE meaning:

*al·ter·na·tive [awl túrntiv ] noun (plural al·ter·na·tives)

1. other possibility: something different from, and able to serve as a substitute for, something else You could take the bus as an alternative to driving. Also called alternate n.2

2. possibility of choosing: the possibility of choosing between two different things or courses of action We gave you the alternative; you decided to stay.

3. option: either one of two, or one of several, things or courses of action to choose between I can't decide which of the two alternatives is worse.

Now, let me clear up a few more things for you. You said:
Most of those cars don't run "hand built exhausts", they instead run either open headers or a turnout right off the header. But when they HAVE to run mufflers,to compete at certain tracks, a big majority run the Vortex Cones. Remember, they can run whatever muffler they want as long as it meets the noise level requirements. The reason I was, as you said, "preaching" about the dirt track cars was to show that these were a widely used muffler in a series where High HP engines are the norm. The late model dirt car has no rear seats for the kids and no trunk for the groceries, I might add.

Moving on. You said:
Ok, we all see how proud of your hand fabbed exhaust that you and you buddies built. That is probably the ideal exhaust for YOUR car, but "I'll be darned" if I am going to put a restrictive, single exhaust on MY car. That left me with the option for true duals which, like I said before, don't fit well under our cars. That is why I chose the the Cones. They are a proven racing muffler that quietens the car with minimal HP loss. I didn't design them and I don't sell them. I just know that they work well, which is proven every Fri and Sat night on late models everywhere, and they don't scrub on every speed bump, etc., like the 3" duals I used to have on the car did.

Then, in desperation, since you were running out of fact based arguements, you said about my car:

Again, You are 100% correct. I think tomorrow I will SCHLAMM!! the front end, to keep it even with the 400# of stereo equipment that I will order to put in the back so everybody can hear my PHAT A$$ BASS 'AKICKIN!!! To Hell with weight transfer, We'z gonna pimpin in da black Z. Maybe I'll trade in the Convo Pro's for gold plated Daytons, yeah hold your breath.

And Finally you inquired:
Yes I do have 3" collectors. And no, I can not tell any power loss on the street. As I said before, though, I haven't took it the track w/ them on it. I am going this Fri, next Wed. or next Fri, depending on weather. I am expecting some power with mufflers, as I said before, just like I would with ANY mufflers. I am going to run the car several times w/ the mufflers to get a baseline, consistent time (I have also changed tire dia on the rear, so I will have to run it a few times to find where it is fastest), and then I am going to take the mufflers out, and see how much the car picks up. I will, leave at the same RPM, shift at the same RPM etc. I am curious myself, but I WILL post true times. If it slows down a whole sec., I will post it, If it slows down a tenth I will post it. I expect a loss, but it is not going to be much. I've seen them on the dirt cars I "preached" about so many times, and they don't drop off any significant time with the Cones in the collectors. These are not a new "gimmick" item, they have been around for years, and are proven to be a good HP muffler. Just because you've never heard of them, you immediately go to being sarcastic, and trying to be funny, ******* on my car, and
and comparing daily driven street cars to 500+ HP street/strip cars(mostly strip). This post was addressed to people who have been though the hassle of having big(3" or bigger) dual exhaust on a 3rd Gen. Some people have them , and love them. That's fine. I simply shared another ALTERNATIVE to going this route, for people who haven't thought of or who didn't even know these existed. I have several E mails from people on this board wanting to know more about them, and what they sounded like. This will be my last post addressed to you arguing about this. This is not what this board is all about. This thread will probably be locked because of this, but instead of being sarcastic and trying to be funny, why not sit back and learn something. Being a SMARTA$$ and being sarcastic, is a dime a dozen, and you've never met anyone that's more of a SMARTA$$ than me when provoked. So lose the attitude, and I will too.


------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

I for one appreciate the info. I've got a Monte Carlo SS with dual "hand fabricated" mandrel 3.5" pipes to 3.5" Borla Mufflers. It's loud!!! Too loud to fire up and drive down the neighborhood at 1:00 am. These look like I could install them in the tail pipes,, after the mufflers,, and be able to drive a little more on the street with this thing than I do now. So,, there are plenty of us out here looking and thinking about "alternative" solutions,,, and I just might like this one. Thanks for the tip "BR".

 

Tell ya what, if you track test with these cones and either don't go slower or >gasp< go faster, I'll post a congrat's and then chow down on heaping big plate of crow. This agreement of course depends on you posting honest results.

The reason I settled on building a custom 3.5" system were because I felt the existing 3" systems involved to many compromises, and I felt the "off-the-shelf" 3.5" & 4" systems were overpriced and included components(like race mufflers) that I didn't want. I felt that building my own 3.5" system was the best solution. The notion came about after I did extensive research on exhaust design(both by gathering a lot of technical info on airflow, fluid dynamics and exhaust theory, and by soliciting the opinions of people who designed and built custom exhausts for a living).

While doing this research one thing that came up often is this: the proper design of the header collector will probably play a more crucial role than any other part of the exhaust(which is not meant to negate the importance of proper design on other components in the exhaust system). With that said, I don't understand how disturbing and restricting flow within and without the collector(which these cones will surely do) would not have a serious effect on the effiency of the collector. Maybe all the info I have collected is wrong, or at least seriously deficient. What do you think?

As for the crack about your '82 sitting fairly high,... you have to admit that's true(it's higher than any thirdgen I've seen lately). Both of my current IROCs have about 4.5" clearance under the tranny pan and they are both on stock-height suspensions. If your '82 is sitting high to improve weight transfer, then it obviously worked as you've posted some really good 60' times. But if it sits high to gain the clearance you needed for duals on a street-driven vehicle, I have to think there would be a better way(like running a larger single pipe.

As for what you've said about the various bends needed on a full-length thirdgen exhaust, I agree with you totally, it severely reduces flow. But running full-length duals is not going to improve that situation, and in fact may make it worse(the greater surface area of duals may not overcome the additional restrictions and flow losses incurred by the additional inside surfaces - especially where numerous changes of flow direction are involved).

Your also correct in implying I don't understand why someone would want to run 3" or larger duals on a thirdgen(or any sub 8000 rpm small block for that matter). Nor would I know the obstacles they face in going this route. Maybe you could inform me as to why pipes this big are necessary on anything less than a max effort race engine(and we won't even get into why pipes of that size will hurt the efficiency of the collectors).

You mention(more than once) the exhausts used on late model dirt-trackers. But by your own description these cars use very abbreviated exhausts that don't have room for conventional mufflers. I'm not sure what this has to do with "full exhaust on High HP street/strip cars". Is it just me or, is this a poor comparison?

Anyways, you're right, this has gone on long enough. And until I see a dyno sheet or a timeslip, you can colour me a disbeliever.

 

I made my own exhaust systems for both my cars, and have researched it some. A cone cant be very efficient because the most important parts of a system are the primary tubes and collector. The gasses speed up when they enter the collector and scavenges the primery tubes, this makes for a efficient header. By putting a restriction or obstructing the flow in the collector you would ruin the scavenging effect, and you said you expect a loss of power. You would be better off trying some bullit type race mufflers, if you can fit them under your car, and you shouldnt loose any power with them. They would olso add some length to your collector, which you need if you are not running header extention pipes. But your post is informative and I'd like to see some drag strip results with your cones!

------------------
91 B4C 305 TPI - SOON TO BE 383
TREMEC 5-SP, STOCK 1-BOLT REAREAND w/342 GEARS, K&N, AIRFOIL
EDELBROCK HEADERS, DUAL CAT TO HOMEMADE Y-PIPE & 3.5" SINGLE PIPE W/ FLOWMASTER, CRANK PULLEY, MSD, FUEL PRESS REG, COWL HOOD, WELD WHEELS
14.1@ 98MPH
-------------
OTHER RIDE
67 CAMARO - STREET CAR, BIG BLOCK, PUMP GAS
350TH w/ATI 10", 12-BOLT w/373 GEARS
10.94@124.13 ON MOTOR - ET-STREETs w/MUFFLERS

 

88IROCs – Man you are some kind of expert spending a self-proclaimed $1200 for that single 3.5” system on a car that the dyno claimed to generate 261 rear wheel horses, huh?

------------------
People who think they know it all,,, are especially annoying to those of us who do.

 

Roc,

I never claimed to be an expert, only that I educated myself before I spent my money. Yes, $1200 seems expensive for the complete exhaust, but you could easily have exceeded that number using off-the-shelf products.

Finally if you'd bothered to pay attention on my old posts, you would have noticed that the dyno run that produced that 261 rwhp was before I put in the new exhaust. I don't know when I'll get the car back on the dyno, but unfortunately the results will be clouded by the mods I have done since, - Iron Eagle 180cc heads and SLP runners - and any that may follow(hoping a new manifold base and a torque converter are in my future, not to mention some rubber that'll prevent wheelspin on the 4-3 kickdown).

 

88IROCs, First of all, I'd like to say that I'm glad this childish bickering (on both my, and your parts) is over. And to be honest, when I first heard of the Cones, I also wondered how putting something directly in the collector could be a good thing. I just became a believer when my boss as well as all the other dirt track guys using them proved to me that they were an efficent, well working muffler. You are obviously an intelligent guy, and I have no problem with you personally. I ordered a set because I had no exhaust on the car since I put in the new engine, and i wanted to drive it around some. There is not but 1 shop here in town that bends 3" exhaust, and they bend it on an old convention pipe bender that probably crinks the pipe down to less than 2" at the bends which is as you know defeating the purpose of 3" pipes in the first place. And according to the NHRA formula for finding RWHP using ET and weight, my car is making 422HP which if you use a 20% drivetrain loss, its comes out to roughly 506 flywheel HP. I have only taken the car to the track twice, and I know there's still a lot more time I can out it with a liitle suspension work and I think the 28" slicks I just put on will help, plus I am going to run nitrous when I get the car tweaked as fast as I can get it on motor. The cam is actually custom ground for maximum gains w/ N02. This is why I shyed away going with a single exhaust set-up for this particular car. In actuality, my car is more of a max effort race car than a street car, I just happen to drive it on the street a little. Maybe when I posted my original post, I was a little vague on what exactly I meant by High HP street/strip cars. I When I get the 350 in my 89 TBI, I will definetly go with a nice single exhaust set-up, I drive the car everday that I don't drive my truck to work, and wherever else. If I go on 100+ trips, I usually take the RS because its much better on gas than the Z71 is.
As to the car sitting a little high, you got me there. Weight transfer is factor, but it is a little higher than I like, but the rear wheels I have are a 15 X 8.5 w/ 3" B/S. I really need some with a 5" or 4.5" B/S so I can tuck the tire under the car, and lower it a little. This is one of those things that when I bought the rear wheels I wasn't even drag racing the car, and I had 8.5's all the way around it w/ BFG radial T/A, and at the time I liked the Wide-all-the-way-around, sticking out look, but now I don't. I just haven't got new rear rims yet. It also looks higher than it is due to the fact the 82-84 Z28 had such small GFX. I have 91 RS GFX, nose, and rear bumper that I am going to put on the car when I get it repainted, so that will help too. But I can't have anyone cracking on my car, man!! But I have no hard feelings if you don't. Opinions are like A$$hloes, any one who doesn't have one is full of Sheeot!! That's what makes our hobby so interesting, because if everybody liked and used the same stuff, what would be the point of doing it.

To everyone:
I am going to track test the Cones, and rest assured, I WILL post true and accurate times. As I said, I do expect a loss, but from what I've seen these mufflers do on other cars,I honestly think it will be minimal. I may be wrong, only the clock will tell. I will post accurate times because I wouldn't want 10 people to run out and buy these and they be disappointed and blame me. As I said before, even if it slows down, I am still happy with them because when I go to track to try to get a best ever ET, I am going to be running the car with open exhaust anyway(unless for some strange reason the car runs the same or picked up with the Cones, which I really don't think is gonna happen). They only take a minute to take off, they are light, and contrary to 3" duals, they don't scrub on the street, which is the biggest reason I put them on in the first place. They also have a unique, deep powerful sound. I will try to post a soundbite soon. I'll keep everyone posted.

------------------
82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

I hear ya about finding a shop to bend large pipe properly(I still gotta cringe at the muffler shop hick who tried to tell me those little kinks won't matter on a 3.5" pipe). What I ended up doing was buying U-bends and J-bends of mild steel, then cutting and welding it back together. I found a shop that had an 8" radial arm saw set-up with a cutting wheel. This was the best way to make sure the cuts were absolutely straight and did't kink the pipe. The cuts were all ground to have 90° corners. All cuts were made on straight sections only, to avoid trying to rejoin curves, when welding the pieces together.

I haven't bothered to track test this exhaust yet for a number of reasons(mostly I'm worried abou torture-testing this old driveline before I get a chance to make the right upgrades), but according to the G-Tech: it's about .1 to .2 sec's faster(depending on temps) than the old TES/Catco/Flowmaster set-up it replaced(didn't hurt that I had another IROC to donate the old exhaust to).

I know some folks will claim welding the joins will introduce flow losses(vs using mandrel bends), but considering the gases travel much slower along the wall, I don't think this is significant enough to worry about.

One last question: I noticed on your web page what you said about running out of motor at 1000', and that you planned to improve that situation with 28" tires and, I was wondering why you decided to go that route rather than go to taller gearing?

[This message has been edited by 88IROCs (edited June 20, 2001).]

 

You directed this question to "Basset" but if I may - From a drag racing point of view, the contact patch is greater with a taller tire compared to a shorter tire of the same width. The taller tire flattens out and also will “crinkle” more at launch providing more rubber to the ground for a longer period of time. So if you have a 4.10 gear ratio and have 26” tall tires,, for sake of comparison we’ll assume proportional radial loading (which it won’t be exactly). If you replace the 26” tire with a 28.5” tall tire, you’ve created an effective or comparative gear ratio of 3.74. So, while cruise rpm and gear multiplication factor would be near identical to a 28.5” tire with 4.10 gears, and a 26” tire with 3.73 gears,, the 28.5” 4.10 gear combination could/should leave harder due to the added crinkling applying more rubber to the ground. Unless you’re running a stiff side-wall tire the taller tire could also “grow” more reducing effective gear ratio,, almost like having a variable rear gear to some extent with the taller side-wall tires. This effect helps some cars more than others.

Also when you’re racing every weekend, tires go pretty quick and are replaced often, if you’re having to heat them up a lot and / or have some grunt. So changing tires to reduce the effective gear ratio (when you wear a set out) is like making a gear swap for a few extra bucks. That is assuming you can get a large enough tire under the car and get the "effective" gear ratio you need. Sure beats the hassle and expense of replacing the gears - if "just" a tire swap will work for you.


[This message has been edited by the roc (edited June 21, 2001).]

 

roc,

very good info you've provided. obviously you know quite a bit on the subject, and i appreciate the opportunity to tap into your knowledge.

i asked the question based on the very small amount of drag racing i have done - kind of of a lay perspective. I did the math before I asked the question and came up with approximately the same numbers as you did - 4.10 gears x 26" tires = 3.7x gears x 28" tires. the reasons I thought the gear swap might be preferable were:
1. i would think swapping gears instead of tires would introduce less driveline losses. while the effective ratio would be the same for each example, the taller tire would add more unsprung weight, which would require more hp for the entire length of the run.
2. i would think the gear swap would provide more consistent and predictable(reliable) results, as the gears should be less affected by differing track conditions.
3. i understand what you are saying about the taller tires being able to hook better, but wouldn't the the extra bite increase the shock loading on the rest of the driveline? it seems Bassett Racing is hooking-up fairly well, based on his 60' times. is it worth the extra punishment on the driveline to go this route? will the extra bite speed up his 60' and 1/4 times enough to risk driveline damage(this is just speculation on my part).
4. the gear swap would seem to be more work and more money initially, but after you've worn out a few sets of tires, how much do you save in the long run(i would think this would be a crucial consideration, unless someone else is paying the bills)?

i'll thank you(or anyone else that cares to respond)in advance for your thoughts. as i said previously, I have very limited experience with this, and my questions are based that limited knowledge. however, if someone wants to share hard won knowledge, that'll make me go quicker, i'll be more than happy to accept.

 

oops, forgot to ask one more question,...

i ran some numbers through the 'puter and based on the data i could gather and some semi-educated(i hope!) guesses. based on his hp, his intended finish line rpm, his race weight(guessed to be 'round 3500 - 3600 lbs), etc.,... the box said his car should be capable of 11.2 - 11.3 @ 121 - 123 mph. at these speeds aerodynamics is playing a big role. the taller tires are going to make his aero numbers worse(right?), wouldn't this have a negative effect on his ET and mph?

 

88IROCs needs to grow up

 

Let me begin by saying if you’re after maximum, to impress times (or sleeper effect) I set the car up with the “smallest” tire I think it will hook on. A lot depends on how much someone wants to spend to hook on a “small” tire. Plus, “small tire” means different things to different people. “Smaller” tires as you mention provides less rolling resistance, aerodynamic drag, and unsprung weight, all reasons valid enough to consider when choosing a maximum effort machine. However, if you’re bracket racing, it really doesn’t matter how fast you go as much as how consistent you are – so IMO you want the largest and widest tire you can fit / afford to fit under the car – within reason of coarse. See,, this way the track conditions you mentioned really are less of a factor. So,, saying this I’ll address your questions or posed them in question form for you to think and research for yourself.

1) What is the weight of a M/T 26x10 and 28x10.5 tire? Does one manufacture’s 28” tire weigh more than the other? What does a Goodyear 28x10 weigh? Is there a manufacture’s 28x10 or 28x10.5 tire that weighs less than a 26x10 MT? Now,, add the weight difference,,, multiply it by that factor need to add unsprung weight,, it’s not one to one,, right? Add that weight into your simulator along with the change in tire size. What did the simulator give you as difference in ET? Does that simulator take into effect the rolling resistance,, if it doesn’t you’ll have to deduct the friction loss and rolling resistance based on another formula,, look for that one also.
2) If you’re really worried about consistency,, big wide tires (bigger and wider than necessary),, takes the edge off variances in track conditions,,, and keeps you from laying under the car and tweaking the suspension adjustments if you have them. Gear ratio and torque converter multiplication factor also plays a part in this of coarse. You want a combo that works together and unless you have someone to trust to give you the right answers, learning these combinations means trial and error.
3) If you’re worried about tearing something up when you increase the bite, you need a different rear end. However, if you’re using the foot brake to launch,, increasing your pre-launch rpm by introducing more of a “load” to the chassis lessens the flash or actual launch rpm of the converter. So,, you can easily soften a hard launching car with driver/launch technique,, if that is a concern.
4) What is the price difference between a set of 26x10 and a 28x10.5 M/T tires? How long does a set of tires last? How much is a set of gears? Will you install them or will someone else? What is the total cost of a gear change? How many YEARS / seasons of racing would it take for the difference in the tires to equal the cost of a gear change?
5) Aerodynamics of the tire / tire-car combo - What is the area in square feet of the tire due to the increased distance from the ground to the bottom of the wheel well / frame compared to a 26 x 10 and a 28 x 10.5? If you were running an open wheel dragster you would need to know ½ the circumference of the tires to figure in the increased area of the tire to add into your program. Now,, Will the front spoiler be lower, higher, or the same if you increased from a 26 – 28” tall tire? How much more, or less air will get under the car now and how much of that will have an effect on the change in aerodynamic drag on the tire?

Yes there is plenty of sarcasm in this response, but hopefully it makes you think enough to get it.

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People who think they know it all,,, are especially annoying to those of us who do.

 

In response to the question about the tires, It was a decision several different factors. The first being that I needed new slicks anyway, the old 26's had many runs on them, and the indicators were almost non-existent. Another reason is that the rearend is relatively new (the gears, I mean). Up until about a year and a half ago, I was running 13.30's w/ a warmed over 350, w/ a set of pocket ported 882 smog heads, a Performer RPM intake and cam, 2400 holeshot convertor, and 3.42 gears. I drove the car everywhere, and the strip wasn't my main priority. Then, by virtue of all the guys I hang out w/ at local cruise ins and the fact that my brother's 3865# full size P/U was kicking my A$$, I decide to go faster. I freshened up the tranny, installed an ACC 4000 stall, 4.10 gears and an old used dirt track solid cam. After these changes, the car was running mid 12's all day long, w/ a best of 12.52 at 107. I then began to build the 383. Also, using the reasoning that Roc said, I knew that 28's should probably be faster on the car with the 383, but I hadn't bought a set by the time I took the car to track, so I ran what I had. But the biggest reasons are that I have 12 bolt Chevelle rearend already spooled, geared w/ 4.10's and has Strange axles, that I am going to have shortened 2" narrower on each than the stock Camaro rearend. I don't want to tub the car, but I do want to be able to stuff 10" wheels under later on. I am also going to spraying the car in the near future, and as it was with 26's, I had to do a really good burnout, or the car would spin, and on the N02, I knew I would have traction problems the 26's. I feel when I do some suspension work, lose a little weight off the car, and with good weather, the car should be capable of 11.20-11.30's on motor. I am planning on a much more aggressive Sloid roller, in the future as well. My cam's duration is only 240 int, 248 exh @.050", and is ground on a 112 centerline. It is more or less a Hyd roller version of a Nitrous HP cam, which is not ideal for max potential off nitrous, but I am fairly impressive with it's performance with no more suspension mods I have, and what the car weighs. I planned on driving the car a lot more than I do when I bought the cam, which is why I went so conservative. But you live and learn

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82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

Wow! Incredibly informative responses from both of you! Got a lot of good info and some really good questions I can chase for answers.

ROC,
I didn't detect the sarcasm in your response, but then again I wasn't looking for it(prolly cause I's trying to think of answers to the questions you posed - ya really got me thinkin now).

Bassett,

Now I understand why you're going the route you are going. Considering the circumstances, it would seem to be the most logical way to go. I want to get more active with racing one of my cars(haven't decided which one yet, though), and what you've done and accomplished so far has given me a lot of food for thought. Thanx.

 

88IROCs,
You mentioned that you were going to get into more racing with one of your cars and you said that you hadn't decided which one. From my experience, which is why I own 2 3rd Gens now, Use the car (if either is) a hardtop, and use the car with the least amount of options. If you get into it heavily, you'll be trying to find weight anywhere you can to get off. The less optioned car will require less lightning, and the car with all the comforts is the one you would probably wanna drive around anyway. I said when I started that I would never make my car unstreetable, but I did. I mean I do drive it some, but it by all definitions, it is an unruly bitch on the street. Get lots of admiring looks though You may even want to get yet another, if both of your cars are extremely nice, and you plan on changing engine, tranny and the rearend. A 88-92 V6 or LO3 RS, hartop would make a good choice. They have a terrible suspension that just happens to be great for drag racing, and in my area, you can 'em cheap, especially the V6 cars. If you are not getting in to the extent of making it a all drag out car, then just mod one of yours, but get SFC quick!!, because by the time I was running 13.30's in my Z28, everything in car rattled terribly( I mean worse than normally, I've had the car for 9 years, and it rattled some when I got it) I was only pulling low 1.9 60" times then. I don't claim to be an expert on these cars, but I have kept pretty good track of what made differences certain mods have made and so forth. Feel free to E mail me with question's, theories, ideas or whatever. If I can help, I'll be glad, if not, maybe collectively we can someone who can. This actually goes for everybody. But I have found the torque arm rear suspension can go fast. There are several 9 sec. cars around the country running with just good springs, shocks, tubular LCA/relocators, and a tubular Torque Arm. There are also a few 10 sec. cars I have seen still running a properly prepped 7.5 rearend. I have some links and articles on some of these cars, when I found out they could go so fast for so little, I really began to feel good about racing a 3rd Gen. I used to wonder if I should go with another platform due to weak torque arm style factory rearend and the less than desirable exhaust routing. Plus there are only a handful of these cars in my area, and they aren't any really fast ones that I know of. Mine is the fastest stock suspension 3rd Gen that I have ever seen or raced against at the tracks I go to, but there may be some I don't know about. My goal eventually is 9's (No Time Soon) My 383 is built from A GMPP heavy duty block (bought from my boss, ex late model dirt car engine) and has an all forged bottom end. It is also fully studded and has steel main caps, so the shortblock will be there. I will progressively upgrade cam, heads, intake, etc. to acheive my goal, but I'm in no hurry, I'm having a blast right now, seeing how fast I can get it as it is. I've seen so many people miss out on enjoying their car because they were too busy wondering what they could BUY to make it faster rather than trying to get the most out of what they had to begin with. I'm sure with a 250HP shot and I good hook, I could get a 10 sec timeslip, but I figure why should I work off an 11.62 pass when I know I can get more out the car, hopefully 11.20's-11.30's. All of the things I do to make it faster now, be benefit me later as well. DAM I love this stuff!!


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82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

 

Right now, the thought of getting more serious about racing is just that, a thought. With the Canadian dollar hovering near extinction, 87 octane pump gas at 72&cent;/litre($2.73/U.S. gal) and home heating and power costs having tripled in the last year, they're ain't a lot of dough left over for the toys. Seems to me, even though my takehome is nearly $50K/yr, I had more disposable income when I made half that. Well enough of the rant.

As for which IROC to go racing with, it's a toss-up. They're both hardtops, and they're both optioned to the max(the only thing missing on the daily driver is factory defrost on the hatch). The daily driver has received the lion's share of the mods, with #2 getting the hand-me-downs. The daily driver has always been modded with day-to-day drivability as the primary concern(smallish 180cc Iron Eagles, LTR's, conservative converter, etc.,...). That being said, #2 would be the better candidate for more serious power(and with less emotional and financial commitment to it's setup this far, I won't mind if it becomes less streetable).

What you and Roc have said will be very helpful, when I actually have a budget again. Right now my main concern is getting some street traction back for the daily driver. It's fantastic for cornering, very good at braking, and an almost nightmare for acceleration. After reviewing what Roc said, I think the problem may lie with the tires(Michelin Pilot Sports - very stiff sidewalls). I'm hoping to cure the problems with more suspension upgrades(all I've done so far is LCA's, PHB, and shocks) without having to change rubber.

Anyways, thanks for the advice and I look forward to picking your brain in the future.

Btw, I reviewed some of my earlier posts in this thread and am considering editing or deleting some of it. I think the comments I made were valid, but the delivery definitely sux. I left them up so far because I figured if someone read this thread, without seeing my posts the way they were made, then comments by people other than myself could be taken out of context.

Whaddya Think?

 

It has been my experience that our cars respond very well to suspension mods, and I wish I would have done more before I put in an engine with as much power as I have. if I were to do it again, I would mod the suspension as much as I could with the 350 that I had in the car w/ the hyd cam, 2400 convertor and the 3.42 gears. I got 13.30's out of it, with no suspension mods except the sway bar removed. I did what little I've done to the suspension when I put in the solid cam, the 4000 convertor and the 4.10 gears. The car may have possibly been in the high 12 sec range with a good suspension A LONG time ago, and in turn, it would be faster now. I also agree with you 100% on the Pilots. I have 335/35/ZR17 Pilots on my RS, and my RS will spin them leisurely. It has only ran a best of 14.91( On ET STREETS), and is by no means what I would consider really fast. It is quick for a TBI 305 w/ no internal mods, but you would think that with tires that size, and a posi rearend it would hook better than it does. They are absolutely awesome in curves though, and they look BADA$$, but I can tell you from experience that it would be a waste of time going to strip on them, especially at with the power you have. The one time I took the RS to the track with Pilots,It spun them out about a 150 feet, and then when they started biting, the car wheelhopped so badly that I had to let up to stop it, which I know is because it had a stock IROC suspension pirated from a parts car. And that reminds me, I found a CHEAP suspension improvement recently. Due to the severe wheelhop I was getting with the RS, I looked under the car, and checked that I hadn't left anything loose, and I noticed that the stock RS torque arm had cutaway "holes" down the length of it. I had never really noticed it, but after I saw it, I remembered my 82 and the 83 I once had had a "solid" torque arm with no holes in it. I decided to "go fishin'" and see if a stock solid torque arm would be better than the one on the RS, and it turned out to improve traction some, but eliminated ALL the wheelhop. My 82 ,at any stage, from the stock LG4 305 to the 13.30 running 350, not once, ever, wheelhopped, but the RS did and the torque change stopped mine. Maybe you should see what your 88(s) have. I don't know what the IROCs had stock, but they may use the same one my RS had with holes in 88, and the 82-mid 80's?? solid ones definetely work better. I made a tubular one for my Z28, and it helped with traction greatly, which is definetly the best way to go. But for a cheap solution to wheelhop, the older solid factory torque arms are definetly worth looking at. I polyurethane torque bushing is a good investment for the $$ as well.

I'd say leave them. You and I had 2 different opinions on exhaust, and instead of using constructive critism to question each other, and then respectfully give our views and opinions, we started a mudslinging battle that became a battle of who could be the biggest A$$. This happens much too often on these boards as it is, and instead of a moderator having to step in and break up a "schoolyard fight" and close the thread, you and I worked it out by stating our opinions, asking reasonable questions, and showing each other mutual respect. Even though this thread has actually strayed some from being an exhaust related post, it is informative, and it answers some people's questions, while raised questions from other's. I have got about 8 E mails generated from this thread, 5 of the 8 are Q's or opinions about the Cones and the other 3 is regarding tire and gear selection, and Q's about my suspension. So I don't think it's a bad thing to leave the thread unaltered, but what you change in your posts is really up to you.

****EXHAUST RELATED**** -- so this thread won't be locked, moved, or deleted

But seriously, due to rain, I did not get to take the car to track tonight. I am anxious to track test the Cones. Hopefully I can go Wed night. There are few guys who have E mailed me that show some interest in the Cones, but would like to see track results before they buy. I hope to get this info as soon as possible. On a humorous note, I drove the car to the parts store yesterday, and a guy there that said he used to own a 85 Z28, asked about the exhaust. He said that he'd tried to get duals run on it but everyone told him it wasn't worth because of ground clearance. After showing him (well telling him what I had done, since you can't see the cones because of 3" turndowns)what had I done and letting him hear the car, he said, and I quote, "I bet there's a lotta guys that would like to know that little secret." I just smiled and said, "Probably so."

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82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.63 @ 113.25, w/ a 7.39 1/8 @ 93.04, and a 1.626 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock
New Best ET: 14.91 @92.9
Bassett Racing

[This message has been edited by Basett_Racing (edited June 22, 2001).]

 

The suspension stuff does get overlooked too much, but it's so much more fun to pump-up the engine. Fun until one night I'm going home after a long day's work, and come up behind some jerk in a Mazda doing 80 in a 100(km/h) zone. So I wait until a safe passing zone comes up then gingerly pull out to pass(trying to avoid a kickdown). As I pull even with the Mazda, doing about 90, I realize the ******** has sped up. I lose my cool temporarily(like that never happens?) and tromp it, instant kickdown and whoaaa! My nose is pointing towards the left side of the road and we almost do the hustle(@ss cheek to @ss cheek). I regain composure, feather it back and get it pointed straight ahead. As I look in the mirror, even though it is pitch black outside and the Mazda is quite a ways behind, I can still see the halo caused by it's brake lights. I don't know who filled their pants fuller, me or the Mazda driver? But it kinda gives you an idea of the extent of the problem.

Anyways, I'm savin' my pennies by stickin' to the truck(it may be a wheezy 305, but it only sux down 1 gallon every 25 -26 miles) and am planning on getting the Globalwest Trac-Link Torque-Arm as my next major mod. I'm told this will help anything less than 400 hp stay well planted. So, it should keep me happy for quite a while.

I dig what you're sayin' 'bout leavin' the posts as is. And despite the negative start, it looks like something positive is coming out of this, judging by the interest you have generated.

Good Luck on Wednesday!

 

Well, the weather finally let me get to the track Fri night and I got to track test the Cones. I ran the first 3 passes with them in, and the car went 11.75, 11.69, 11.72 respectively. I took the Cones out, and went 11.62 and 11.64 I did some tuning on the engine before this weekend and even with 90 degrees+ weather with 100% humidity and a 29.96 baro. reading, the car picked 1.2-1.6 MPH (the best being 116.05)w/ the mufflers out. It was so hot and muggy the track absolutely slick. My best 60' time on the night was a 1.71 and last time I went was it the 1.62-1.64 range all night, so if I could have got the hook, I would definetly been able to better the 11.60 The Cones cost me a pretty consistent tenth. Although I expected a loss, I would really like to run them on a night when the track was hooking better, because I spun much worse with the Cones in, which indicates to me they may have boosted TQ a little. But the timeslip doesn't lie, they killed a full MPH, which clearly shows they cost around 10-12 HP. I still consider it a good mod because they keep the car quiet on the street, and it took me about 3 min to the them off. One of the guys I race with took off his dual 3" exhaust w/ a custom mandrel bent X-pipe and Flowmaster 2 chambers on a chassis dyno, and he said the he gained 11HP with open headers. His exhaust cost around $500 and mine was $120 so the Cones aren't all that bad.


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82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.60 @ 114.56, w/ a 7.34 1/8 @ 93.50, and a 1.622 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock

Bassett Racing

[This message has been edited by Basett_Racing (edited July 07, 2001).]

 

Coupla thoughts:

1. The holes in the mesh seem awful small. Perhaps elongating some of the holes, or joining some adjacent holes might improve flow a bit. Adjusting the holes near the front(outside) should have less effect on increasing sound.

2. Perhaps beveling the edges of the holes with a conical stone(and a flex head grinder) might improve flow, without increasing noise. The sharp edges would cause a lot of friction, and bevelling the front of the holes should smoooth flow past the cone.

Both of these suggests would obviously involve a fair amount of work(on the plus side, if you have tools, the cost would be zilch).

 

Those are some suggestions I hadn't thought of. I had planned to increase the hole in small side of the cone. This pic above doesn't show it that well, but there is a hole in the small end about 3/4 in dia. I though about cutting the whole end of the Cone a little and increasing the hole size.

On another note, I saw a thirdgen with Flowmaster 1 chambers tucked up into the indentions in the floorpan where the rear seats sit. It was the most tucked 3" exhaust I ever saw on a thirdgen. It didn't seem to hang down any lower than a good 3" single system. It sounded wicked!! His exhaust looked to bent on a conventional pipe bender, and had some kinks, but it were a welded up, custom job like your's, it would have really been a KICKA$$ set-up. He said the car ran the same ET w/ or w/o the 1 chambers. I may look into doing something like that later on.

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82 Z28 383, Ported 215cc Dart Iron Eagle Heads 72 cc Comb. Chambers, Comp custom grind Hyd roller cam, Speed Pro .250" domes, Wheeler Motorsports 4340 I beam rods, Eagle 5140 steel crank, Weiand Team G intake, Holley 830 DP, hedman headers
Trans: Turbo 350 w/ 4000 stall -- Rearend 7.5 w/ Richmond 4.10's, Auburn Minispool
Best ET:11.60 @ 114.56, w/ a 7.34 1/8 @ 93.50, and a 1.622 60'


89 RS, L03 305, Hypertech Chip,cat delete, Dynomax exhaust,K&N open element Filter,160 stat, MSD coil --Trans:700R4 Corvette Servo -- Rearend: 7.5 GM 3.42 w/ posi-lock

Bassett Racing