Finally got the turdgen on the dyno.. Rev extreme on Palm River rd...
first run was 200hp.. so then i took off the air filter lol.. 205... then 3rd run was 216hp/253tq.. so im not even sure what to think of these numbers.. really dissapointed but actually what i expected... anyway i wish the dang scanner worked so i could show everyone exactly whats goin on.. and I think my GF may have thrown it away.. she will get it lol. for my combo this just really bites I gotta do something

 

what's your combo, list it out, something isn't right 216 is low for a 355. And what did you do to gain 11hp on the third run? The numbers aren't consistant so there is some tweaking to be done.

 

216RWHP? That's almost 300hp. For a basic, mild build I can believe it.

 

well with a 355, dart iron eagle 180cc intake 64cc combustion chambers, 224/230 cam with .505 lift ish 112 lsa, stealth ram intake, stock tb, stock lifters, old school getto slp headers and a 3" mandrel bent y-pipe

i only made 275hp/315 ft lbs

i think i can easily pull an extra 25-35 hp out of the motor with a tb and a cai, that stock air box is real restrictive.

but ya lotta parts on that motor, not as much power as i hoped for either, and im pretty damn close to sea level. Thats also with a custom tune mind you it was just a rough tune the a/f was going a little lean up top.

what heads are you using? my combo lacks cause these crappy iron eagles only flow 209cfm on the intake side, not sure why i bought them, shuold have got some edelcraps.

 

is that 275RWHP or corrected to flywheel HP?

If that's RWHP i'm impressed.

If flywheel i'm somewhat dissapointed.
Reason I ask is that I have a similar cam, similar flowing heads, etc. I'm curious what i'll be putting down when I get it dyno'd this summer.

 

thats on a chassis dyno, to the wheels.

Numbers arent bad, with a TB, better intake box, and some porting to mainly the intake side of the heads, guaranteed id be well over 300 hp to the wheels.

only other thing that im still trying to figure out, i know the iron eagle 180 heads take a 1204 gasket, and im not sure if the stealth ram takes a 1204 or a 1205, if it takes a 1205 then my heads are seriously shrouding the intake.

 

The dyno can be a heartbreaker for a lot of people. What does your car run at the track??? Was it a Mustang Dyno or DynoJet unit?

FWIW,
My car weighs about 3650 down the track and goes 115mph at our altitude.
According to the online calcuators/"Moroso Slide Rule" it makes ~430rwhp. On a Mustang Dynometer i put down 376rwhp.

http://www.race-cars.net/calculators/et_calculator.html
http://www.timmcamis.com/cool_stuff.html

 

Hi im in clearwater...was going to take my IROC to them for some pulls. Just wondering what you thought of the place as far as service?

What is your motor setup?

 

275whp aint bad for those heads.... probly have a bit more in it tho..but the heads are killing you.... you have a 330+whp combo well tuned with ported heads or aftermarket heads that will actually flow alot. I've seen heads/cam LT1 cars with that cam make around 340-350whp with that cam. stock headed cars with the bigger 230/244 cam only made 352whp... there u can see the limitation on the heads.. you need flow


your stall is one reason the number was so low. 87 TA was doing 125mph and he only put down something like high 370's-380s if i recall right. in reality it was more like 450-500whp based on his track times. his loose converter took out some of the numbers

 

Man....

That's heartbreaking. I'd be throwing stuff through windows, if I had THAT MUCH money tied up in something, and that's all it did.

My 305: 237 RWHP & 267 RW ft-lbs

Stock Q-Jet


Something is seriously wrong with your car. It's not the motor. Stopped-up cat, throttle not opening all the way, something along those lines. Your combo should do about 275 HP and 320 ft-lbs to the wheels. Easily. Maybe more.

Look for simple, obvious, stupid stuff. I'm betting there's one goofy thing wrong somewhere, that you've overlooked.

The heads AREN'T the problem. Neither is the cam.

 

it dynod like 279 hp/315 ft lbs to the wheels

Thats with stock tb and air box, both of which when they get changed out i think will be good for 20 hp to the wheels.

The heads are currently the biggest restriction, exhaust side they flow ok but intake is 209 cfm, not good numbers at all.

 

Humm Dyno Drama I'm not looking forward to doing mine

400sbc stock
2.02 port and polished heads
510 lift cam
stainless valves.
need heads. and roller rockers
holley 750dp


Anyone wanna throw out a guess what it will make

 

So let me guess.... these are 882 casting and the .488"/510" 234°/244° cam?

If that's what it is, I'll buy the 230 RWHP / 275 RW ft-lbs square in the pool.

 

My comment was directed at the original poster. But since I got your motor combo confused with his post, I'm all mixed up. We don't know WHAT his car should have done yet, because we don't yet know what his combo is. For all we know, he might have a 2.8, in which case he's laying down the smack on some people.

Doug, sounds like yours is about in line with realistic expectations.

 

Like i said there is probly some more to be had with simple tuning...but the heads only flow 209 cfm... thats only just a tad bit better than L98 aluminum heads and just abit worse than LT1 heads. i think 300whp would be pushing the limits of that combo with those heads. i know some full bolt on LT1 cars making around 300whp and some making abit more than that with excellent tunes. LT1 cam is tiny... but when they go to CC306, they make 350-360whp on stock heads. only 50hp gain in most cases. thats a huge jump in cams. the heads are realy holding it back. the 224 cam would probly only make 325-330 in a LT1 stock head, but i'd have to see some dyno results. his combo is using worse heads so i could see tuning picking up some power but dont expect more than 300whp

if i had that much money tied up in that combo, yes i'd be dissapointed but i would never use dart iron eagles to begin with... there are much better choices out there



now i'm gettin confused...what is the original posters combination??

 

I'm getting lost with all the posters here.

Gibson should be able to do better then 230RWHP with a 400cid.

216RWHP for Chris 5k - we have NO IDEA what his combo is. So it's hard to say if it's in the ballpark. Chris, what's in it???

Are you talking to Doug here sofakingdom? He DID do 275hp to the wheels? Were you expecting more? Or did you mean the original thread poster, with 216HP? (do YOU know what he's got in it?)

EDIT: up to speed now...

 

https://www.thirdgen.org/forums/engi...tec-build.html

by looking at this thread, i could see a 224/230 comp xe268 cam, vortec heads, 650 speed demon dp, somewhere above 9 to 1 compression, and performer rpm manifold

definately should be WELL over 216whp. more like 300whp. my buddies LT1 cammed vortec headed 350 ran 13.5's at 99 in a big 83 shortbed truck. estimated 350hp on motor. you have alot more cam than him but he had a 750 dp carb

 

[QUOTE=19doug90;3216706][QUOTE=sofakingdom;3216697]Man....
Something is seriously wrong with your car. It's not the motor. Stopped-up cat, throttle not opening all the way, something along those lines. Your combo should do about 275 HP and 320 ft-lbs to the wheels. Easily. Maybe more.
Doug: you're sure right about the Dart 180cc heads. i got the same 208cfm. Sucks. The big *** valve guide boss in the intake port is the main offender. After full porting was able to get a semi descent 248cfm. At least they are as good as 180cc out of the box Proaction heads now.
My buddy bought these heads for his boat cause they were cheap. (so he thought.) Wait till he gets my porting bill.
Should have gone vortec like I told him. these non platimum series 180 Dart's suck. Not on my best buy list that for sure.
Probabily not the whole cause of the posters dissapointment but they are contributing.

 

Ok, so NOW I can agree with that. That's a better (yet in the same ballpark) combo as i've got, and i'd be throwing a FIT if I only dyno'd 200HP. (even at 4000' elevation).

 

okay this is the end of stuff about my car, sorry didnt mean to steal thread, the dart heads blow nuts, im eventually going to sell them and buy either some brodix heads, or edelbrock rpm heads both are very nice.

ya hopefully i can squeeze close to 300 hp with a tb, cai and some better tuning, but for now itll be more then enough for me to kill myself in, im only 20

 

I dynoed the setup with a 2800 stall and a 3500 stall and both times was right around that 375 mark. I haven't strapped it down with the latest converter yet though. Maybe it will be even lower.....not taht it matters.

 

I got 251/318 rw with the stuff in my sig ( minus turbo ) with no tuneing . Something is wrong .

 

Sorry for not listing guys...

350 .030 over
vortec heads
edel airgap intake
demon 650 dp
comp cam xe268
hooker shorty headers and y-pipe
the rest of the exhaust is crappy 2.5"... no cat.
oh MSD 6a... mallory dizzy.. mech and vac advance..

using the accel shorty spark plugs.. and the main reason I got the thing dynoed was because its stumbling off idle and sometimes falls on its face when i jab the throttle... so Im thinking the powervalve is not opening soon enough.. and something else is going on..(maybe pumpshot?) anyway the graph confirms lean until after 3500 rpms (16 a/f) then gradually goes down to 14 at about 4250.. then stays deadly consistent.. so thats why im thinking powervalve.. but I was still hoping for more power lol..

 

What kind of stall you have.

 

I forget which magazine it was, but there was an article about the accuracy of various methods available for determining horsepower. From best to worst, the order was:

1. Engine dyno.
2. 1/4 time & MPH
3. Chassis dyno
4. Evaluation of installed equipment

There wasn't a big difference between #1 & #2, or #3 & #4. The biggest difference was between #2 & #3.

 

Your car stumbles because of the distributor timing curve and the carbs accelerator pump setup. Let the motor stabilize on the dyno before reading the AFR. I believe a Mustang dyno can load down the motor to a specific rpm and step thru the band. Your AFR is very lean. Should be 13.1 to 12.5:1 at WOT. Manifold leak , fuel pump capacity or jetting. The power valve opens right away when you floor it reguardless of its stamped number cause manifold vauum drops immediatly to 0. PVCR could be plugged thu. the power valve only changes the fuel enrichment transition point from Part throttle to WOT.
The exhaust on your car really sucks. The hooker Ypipe sucks. going into 1 2.5" exhaust pipe is really killing it. Make your own 2.5" into 3" or 3.5" system using a Flowmaster Y collector. Summit # FLO-Y250350 or #FLO-Y250300

Even thou comp says the XE268 works with a stock converter ya really need a high stall converter. A good 3000 stall lock up converter would rock. Forget modified, restalled 12" converters, you need one based on a 9.5" or 10" case diameter . ATI, or Yank. ya get what you pay for when it comes to th700 converters. The other option is to change the camshaft for one that really does work with a "stock converter" stall speed. What stall are you getting now?
Are you sure you have the right .708" reach spark plug for vortec heads? Y do you need shorty plugs?
Have you ever had this car to the track?

 

I'd be a bit upset with 216/253 with a 355ci motor since my little 305 put down 195/273.

 

My blower motor before the ProCharger put down 239 / 338. That was with a stock 8:4:1 compresson L98 with a small blower cam on the stock tune.

 

i dont know jack about carbs so if thats your problem seems like people know the answers already, vortec heads flow way better then my 180 iron eagles, you have a good intake and a descent sized carb, not to mention i only have a 274 cam not much more then you, theres nor eason you shouldnt be dynoing near 300 hp

 

I think I have a vette converter 22-2400 stall but throttling it from a stop the rpms definately dont flare over that.. sorry if this doesnt make sense I just got home from a 12.5 hour work day.. anyway I really dont want to change the cam.. or the converter for that matter lol. I know that would help, but I want to get some more power.. right now it wouldnt be worth the money for a stall making 216 horses lol.... I think your right about the dizzy curve, i noticed my car wants a lot of timing to idle good and have good throttle response... yet kicks the starter when I set base timing that high.. so that means weaker springs on the mechanical advance right? as for the jetting.. that sucks because I dropped the primary and secondary jets 2 sizes.. so should I go back up 2.. how should i handle the dizzy curve, just slap on a weaker spring or is their more to it? Thanks in advance guys I will go cry now haha

I belive someone asked... This was on a dyno jet

 

MIKEH that was my first time seeing or having a dyno run.. so I really cant give too much info as far as their skill, but they have decent customer service.. no complaints

 

The problem is not the "stall".

It's not the "power valve". The power valve is just that, a valve. It does not control the AMOUNT of fuel that's delivered, but rather, only WHEN (at what vacuum) it's delivered. Given that the car is at WOT during a dyno run, i.e. ZERO vacuum, i.e. the PV is GUARANTEED to be open, it's not possible for it to be the culprit, unless it's totally defective and fails to open which is not their normal failure mode.

If you have inadequate fuel at ALL operating conditions, as it appears you do, you need larger jets. Most engines want a fuel mixture near 13:1 for max power, almost always somewhere between 12.7:1 and 13.1:1. You need to increase the amount of fuel your carb is metering by about 8-10% to get there; meaning you need a jet size increase of about that much, as measured in cross-sectional area. That's about a 5% increase in jet diameter. Meaning, if you take the carb apart and see 70 jets, you need to step up to about 74.

What is the timing set to ACTUALLY? How do you know this? How did the car respond to changes in it on the dyno? What happens if you advance it to where it starts to ping and then back it off until it quits? Do you have a stock crank damper and an aftermarket timing cover/pointer? Do you know that your timing mark is accurate, as it almost NEVER is?

The dyno operator should have been able to tell you all these same things. That's why people take their cars to the dyno, after all... well, at least some people, maybe others just want to hear what their car sounds like while it's running ***** to the wall, and are willing to pay $75 to hear that 3 times. But what do I know. Anyway, this kind of advice is what you were paying for, not just the rent for the piece of machinery. If you didn't get it, then the operator wasn't doing his job, and you didn't get what you paid for.

And, like I said earlier, look for the obvious stupid stuff. Have somebody sit in the car and push the gas pedal to the floor, and you observe the throttles and make sure they're wide open. You wouldn't believe (well, maybe you might, but I doubt it) how many races have been lost for something just that simple.

You're nearly 100 HP and about 75 ft-lbs low, for your combo.

What RPMs did the peak torque and HP occur? Looks to me like your peak torque SHOULD HAVE been around 4400 RPM, and peak HP SHOULD HAVE been around 5400.

 

You want that high(er) initial timng at idle. more the marrier.
That means you have to limit the travel of the mechanical mechanism. Read the Mallory instructions. Advance limiter stop Either a bushing or a wedge type thingy depending. At any rate it is adjustable. Yes you have to do more than "slap in some weaker springs" As for the starter with increased initial advance you can buy a "Starter Saver" from MSD that automatically retards the timing while starting the motor to ease the effort on the starter. I just use a switch to disable the spark power during hot cranking then throw the switch and it fires right up. But the MSD "starter saver" is sweet. its an add on for your MSD6. MSD#8984
I suppose you don't want to rework the exhaust either. Ya don't leave a lot on the table.

 

Quit racing dynos and take it to the track. Only way to accurately tune and measure for horsepower is on an engine dyno where all conditions and parameters can be monitored and controlled. You cannot take WHP and multiply it by some magic number to calculat FWHP. Too many things to take into consideration. Everything that you bolt to the engine is going to eat up HP. Front accessories, headers, exhaust, converter, gears, drivetrain weight, seals or anything else that causes friction. Tire height will have an effect on WHP numbers, so will tire pressure. The brakes will drag and eat up HP. If you've got new u-joints and bearings in the drivetrain the extra friction can eat up HP. Not to mention the viscosity of the fluids in the rear and trans. Are you keeping the coolant and oil temperatures inside the engine constant between each pull? Probably not. Use a chassis dyno for what it is meant for, tuning the drivetrain and basic engine tuning. It is NOT an accurate measure of HP. Not to mention the weather. The weather conditions can have a huge impact on HP numbers. If the barometer was in the sh!tter the day your car was dyno'd and the numbers are uncorrected then they will read lower. If your dyno operator is on the ball then he should have adjusted the numbers.

 

I'll give you an example;

When I finished my motor it made 425 FWHP, corrected. I got it in the car and put a few miles on it. Had a new trans, 3500 stall converter, new steel driveshafts with new ujoints, conventional trans fluid and gear oil, rebuilt rear with all new bearings and seals. I got the car strapped onto our Mustang chassis dyno and brought the engine temps up to the same as they were on the engine dyno. First pull it made 350 corrected HP. That's just around 20% loss. A few weeks later after a change over to Royal Purple synthetic fluids and a few hundred miles on the bearings it made 387 corrected HP. That's around 9%. I'm just trying to show you that the standard 12-15% isn't so true.

 

yeah thats all good an all, but even if his dyno variation exceeds 50hp from pull to pull, conditions to conditions, his numbers are STILL low. his combo should be making upwards of 300whp well tuned... something clearly aint right with the tune

 

One of my points was who gives a **** how much power it makes. How does it run? I've seen plenty of cars with gobs of power but are terds at the track. I've also seen cars that make less power run their ***** off. It's not how much power it makes, but more importantly, how fast does it acclerate?

 

Dialed in... if you read the first post carefully you would have noticed I mainly had the car dynoed for the a/f reading.. and also just for the hell of it.. but at anyrate... I knew something wasnt right and its not running like it should... or as fast as it should. After being walked by a 14 second car on the street I got really suspicous and its becouse my top end power blows nuts..

F-Bird.. I was planning on a Hooker Cat back.. just tight on money lately.
the reason I use the shorty spark plugs is becuase I hate spending 20 minutes to get out one damn spark plug with a wrench... what plugs should I be using?? I will change for power...

sofakingdom.. The reason I say my stumble is caused by the power valve is that it was excessivly lean until the dyno operator went WOT.. which leads me to believe my power valve isnt opening soon enough (before 3500rpms)
and causing it to buck in high gear with very light throttle... Timing.. I do not know Exactly where it is set.. I installed the wrong timing marker. with a summit balancer. Peak horsepower @ 4900 then falls off after 5K Peak TQ @3900 and I did not try to change the timing while on the dyno... I know kicked myself in the nuts.. and as someone asked.. I didnt do anything different from run #2 and #3 .. after run #1 i took off the air filter and assembly.. and went from 200.27/241.81 to 205.89/247.32 then on run #3 for whatever reason... 216.76/253.90

 

You're not listening:

The power valve operates on the basis of VACUUM. It's closed when the vacuum is above whatever its design value is (which is one of those tuning things), and opens when the vacuum goes below that value. The idea being, that that particular vacuum is the approximate dividing line between cruising type conditions or other light load, and WOT or similar heavy load. Since at WOT your vacuum is ZERO, which is of course BELOW the PV's operating point no matter what PV it is, IT CAN'T CAUSE WHAT YOU'RE SEEING.

In fact, when your power valve opens, you're getting about the right proportion of enrichment; about 10-12%. Your mixture goes from 16:1 to 14:1. That's about right. Once you get your jets right, the PV will make it go from about 14.5:1 to 12.8:1; which is just about perfect. Jettign properly will also cure the stumble and the part-throttle hesitation and flat spots.

Sounds like your timing mark is completely fornicated. So, screw the timing light, because NOTHING that it tells you has ANY meaning. Advance the timing until it starts to ping, then back it off until it quits pinging, and see what it drives like. I can assure you, the engine does not whup out its timing light, read the mark, and decide how it's going to run based on the "number" it sees; so you shouldn't try to tune the car that way, either. Give the engine what it wants. It will tell you, in no uncertain terms, when you're screwing up. Which is EXACTLY the message it's sending you when it saysIt's telling you it's NOT HAPPY. Tuning is the process of adjusting all the control systems (fuel delivery, ignition timing) until they match the engine's needs.

If your starter is inadequate, get a better starter. You don't mis-tune a motor to "make up for" an inadequate starter. That's just boneheaded. ANY mini-starter is better than the stupid stock POS from the Stone Age that these cars come with. All of the minis, whether the late-model Delco one such as the LT1 uses, or any of the aftermarket ones that are built off of either the Hitachi or the Nippondenso motor, use gear reduction. Get rid of that dumba$$ direct-drive Delco POS and put something decent on it, and tune your car where it needs to be tuned.

 

find absolute TDC then look where the pointer is reading. I've seen factory pointers off by 10*. Any competent engine builder will set the pointer properly before buttoning up the motor.


sofa is right. Only way the PV could be the problem is if somebody went in and opened up the PV channel. During part throttle cruising the motor is running off just the jet. When vacuum drops the PV opens and lets more fuel flow into the primary venturis. This lets you run a small jet in the primaries for better mileage. If it drives ok but is too rich at WOT try coming back on the secondary jets.

I'm willing to bet that most of you problems are timing related. If your timing is off it can throw off the carb and you'll be chasing your tail forever. Take the car to a COMPETENT shop not the cheapest or closest, and have it tuned properly. A good dyno operator would pick up on any of these obvious problems long ago.

 

With not a lot of hours on it I might add. So the engine was tight, and 30 mins of cam break-in time is still negligible when it comes to seaking and losses.

which breaks the engine in even more, so it has less internal friction.

Hummm..... +37 hp from a few hundred miles and new synthetic fluid. You could make an advertising commercial for Royal Purple with those numbers.

But seriously, the extra power came from the lower friction and better combustion seal at the rings, and very little of it from the new oil.

Apples and oranges. The extra miles, plus the swap to Royal Purple, were collectively the reason for the extra power... as well as any additional tuning you did (but neglected to mention). If you removed the engine from the car and re-tested, it would be more than 425 fwhp.

Don't be too quick to assume the 12-15% is wrong.

 

Went to the parts store today, to look at the difference in spark plugs, looked up stock plugs for a 96 camaro, and they were ngk tr55 so i bought 8 went home and pulled a plug to compare, and sure enough those accels for the old style head were way shorter than the ngk's... so hoping this was a miracle cure my engine needed I swapped them all out.. and felt like a complete *** for not getting the right plugs the first time .. wether its the right plugs or what the car drives better, not bucking like it was.. so thats great maybe picked up a few ponies too, but it still needs work. sooo my next step is to jet up. soon as i get the gaskets and such. right now im running 68/76 which means stock were 70/78 I dropped the stock jet sizes 2 in front and rear..should I just go back to stock? I know what you mean about tuning around the weak POS starter, but right now its all i can afford man, so ill tune it right and they may keep dyin on me but they have a free replacement. just so u know im 21 and in an apartment with a gf of almost 2years so money is tight

 

does not haveGo get the right spark plugs; or at least, check to see if the ones you got, just accidentally are correct for the heads you've actually got. Look up plugs for a 97 Chevy truck with a 5.7.

As far as jets, go up 4 sizes from whatever those dyno readings were taken with. The dyno tells you what's wrong and what you need to do. Don't worry about "stock", worry about what your engine is asking for. Put the size jets in, calculated as above. Judging by the A/F ratio numbers you posted, just that one change alone will make your car radically different.

Then advance the timing until it just starts to ping at moderate load in high gear going up a hill fully warmed up; and back it off until it just quits pinging. There's no guarantee of course that that's "perfect", but it should give you a good baseline starting point. The engine will tell you what's right or wrong. As you advance it, the engine will run better and better; as long as it keeps running better, keep advancing it. "Runs better" is the engine's way of saying "you're doing the right thing". When the engine starts pinging, that's "Enginese" for "too much timing"; so back it back off. Forget what the timing light tells you, since the light isn't what's making HP (or not); and listen to what the engine tells you instead.

This is not rocket science here. It's just a car. It's pretty simple. To put it in perspective, as stupid as I am, if I can figure it out, then your average Borneo orangutang should be able to figure it out twice as fast. Surely YOU can handle it.

 

Had the funny felling you had the wrong plugs in it.
Wouldn't be the first time someone assumed that vortec took the sameold plug as most GM heads.

How does it run now. make sure the plug gap is correct .035" is best. I use Champion RS10YC or RS12YC bu the the NGK's are fine.

having run a few motors with vortec heads I can help ya get the ignition advance dialed in easier and better than "advancing it till it pings"

Vortec headed motors for the most part many times need less total timing than other head designs to make max power. Many times they want and need no more than 30deg. The range will be 30 to 36deg total at high rpm.
Any thing more will not make more power even thou it may not ping when set like that. (more is not better) Try it at 34 to 36deg. Then try 32deg. if it runs the same use the lessor timing. That is all you need.
That being said, your throttle response and low rpm and idle quality will benefit a lot by increasing the initial timing at idle a good bit. It will want 18 to 24 deg. Usually the more timing at idle, all the better. Then it needs a smooth stable advance curve from that point maxing out at around 3000-3500rpm.
Very radical advance curves with the lightest springs tend to be unstable and don't make ya go faster and tend to ping with vacuum advance. A curve like I suggest works better overall.
Yes return the carb jetting back to "stock" then work from there. I think that now that you have the right plugs in 'er and correct the ignition curve you'll get a better dyno result.
Uncap 'er on the dyno and see just how bad your exhaust system is. Shorty headers can work ok but the Y connection is critical. Long tubes (even with a proper Y pipe make more power and lots more torque) much better match to your Comp cam.
The "right" carb jetting (for your car) should be within 4-5 jet sizes from stock. if not something is not right. Many times the stock out of the box jetting works just fine.
try slightly richer jetting but not untill the timing is corrected. Do one thing at a time. You cannot evaluate 10 changes at once.
in my opinion all the availble aftermarket "cat back" systems suck for what rhey cost. Your motor is capable of making serious power but you eed an exhaust system that won't restrict that. Trouble is all the poular systems while easy to buy and bolt on are made for near stock motors. You need somethng like this. Use your Hooker shorty headers but build a 2 into one merged exhaust using a Flowmaster Y collector 2.5" pipes into a big 3" or 3.5" main pipe would be sweet. Twin 2.5" high flow cats would be sweet. Nobody makes a out of the box system like this that I know of. You either have to build it yourself or get a exhaust shop that is capable of good custom work ot build you it. Do you need to run a Cat converter in Florida?
I know this is a pain but buying an overpriced bolt on cat back that is just ok on a 250-275hp motor is not going to get you the power you should have. You'll probabily be disapointed.
The camshaft and total exhaust system have to work together for the whole thingy to come together.
The performacne exhaust companies market the systems that will make them the most profit. (sell the most) That means easy bolt on replacement systems for near stock motors that are emissions compliant. Think about planning out and building a custom system that will make your car rock.

 

He basically has no timing mark. Not really applicable. Great idea, won't work here.

Ya gotta start SOMEWHERE. "Advance until it pings" is AHELLUVALOT closer than 35° retarded, which is about what his current mismatched timing mark combo has it set to.

 

great Idea but will work. Better than trying to set it by ear or using the butt dyno.
If the balancer is not marked for 30-36deg then you can simply get a (Mr. Gasket) balancer timing tape and stick it on. Not hard or $expensive$. You can even measure and mark the balancer your self. using a hunk of Masking tape. Not hard or expensive and will work just fine. Can help him with the math and method if he wants.
the timing marks are probably ok. Having the wrong plugs in it was probabily really messing it up.
There is no need to try and set the timing with your head in the sand, making things a lot harder than they need to be.
Sorry if I offended ya. Just trying to bring it together for the poster.
i realise the stock crappy GM starters tend to not want to crank over well when the initial timing is cranked up and the motor is hot, but there are some good simple ways of getting around this. Lots of people with motors with hi performace cam that like a good bit of intial timing have this problem with GM starters and get around it using either and MSD "Starter Saver" cranking retard device or just a simple power switch to disable the spark while getting it cranking. Not hard to do.
Ford factory ignitions have had a cool built in cranking retard function on their cars for years (Duraspark II) . Don't know what GM's problem is.
It's not rocket science.

 

Who said anything about 30 minutes? I played with that thing on the dyno for over a week. It had a lot more than 30 minutes on it. The motor had 23 full pulls, plus initial break in and several aborted pulls before it even came off the dyno stand. Compression and leakdowns show the rings were seated During those pulls the motor oil was changed to RP Racind 21. That alone picked up 2% HP so I guess I could be a spokesperson for RP
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I wasn't attributing the power increase solely to the fluid change. My point was that every car is going have a different amount of drag in the drivetrain. This was proven by the fact that the car was driven, the bearings, u joints and all had time to wear in. The friction was reduced and it freed up some more power.

 

No offense!! I respect your opinion as an experienced engine builder, as I hope you respect mine. Your advice is exactly right, right on the money. You're 100% correct that the Vortec heads typically require a couple of degrees less timing than other heads, and that the ping method doesn't always yield a perfect setting. I think we just have a differing view of the quickest and most practical way to get to the perfect setting. I happen to think it's a WHOLE LOT easier to advance it until it pings, then back it off till it quits, than to futz around finding TDC and sticking tape on stuff and all that. The next advice after finding the advancement at which pinging quits is of course, to back it off some more until power begins to fall off noticeably, then advance it back slightly. Let the engine speak! Listen to what THE ENGINE says the timing should be, and screw the numbers.

But regardless, the combo is good; clearly there's some tuning needed. I think we agree on that much. Once Chris figures out what inputs he can grab and move around, and what effect they have, I think he'll be well on the way to unlocking the missing power.

 

well put.... have a great day.

 

Hey guys, I really apreciate all the help and advice your giving me, im just trying to keep up with all the ideas and work at the same time...
ok so heres the deal. not saying that im that great of a tech, but im sure my timing isnt 50 degrees retarded would be funny though.. and guys ive been screwing around with the tuning on this car for a few months, and recently swapped msd boxes due to lack of spark, and what a PITA to be trieng to figure out how to get more power out of your car when the msd is doing super weird ****, or nothing at all lol.. so I didnt turn to you guys till the dyno because I was ready to light a match on this project.. The timing I think is set really close, maybe a very light ping, and i was running 89 octane before.. changed that to 93. so ill leave it alone for a bit. now.. one question I have.. my demon carb seems it may be leaking a small amount of fuel out of a idle mixture screw, cant this leak vacuum? I will check the entire intake aswell.... the method I've always used was to spray around with starting fluid, any other suggestions? THANKS TO EVERYONE

P.S. 10239906...96-up...350.........."Vortec 5700", "L31", 64cc chamber,
170cc intake port, 1.94"/1.5" valves
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Oh and I forgot to add that my top end power still lacks a lot, sooo drivability is better so thats good but the seat of the pants dyno isnt throwing me any real impressive numbers lol jetting will be soon promise.... and Im gonna get this damn dyno graph on here..