hi everyone.WOW a site just 4 us!well here is what i have.i bought an 87 iroc-z.it came with 305tpi.at the time i didnt know ANYTHING about what makes a car fast.i felt it was kind of quick but i knew i wanted more. so i swapped in a 355. here is what i have. 87-95roller block,rebuilt,bottom,sealed power flat top short skirt pistons,LT4 hot cam-218in-228ex@.50 525in-525ex lift-112lobe. lunati 7.290 push rods. procomp stainless steel 1.6 roller rockers. procomp 190cc heads. professonal products intake-idle-5500. summit racing 600cfm carb. carb is jetted . and has 50cc accelerator pump .accel super coil. msd8.5 wires. hooker shorty headers,dynomax 2.25 true dual exhaust. i plan to add rpm air-gap intake,an a holly 670cfm street avenger carb. my trans back is stock. i plan to beef up 700r4. i like having over drive. i dont know what rear end or gear to go with. the car is very quick now,its a HUGE power jump over when i bought it. so any advise? i would love to read what u think about the combo,parts,hp,torque,rear end,and things i should do.im hoping im making about 400 ft lbs torque

 

"im hoping im making about 400 ft lbs torque"

Is that for the flywheel or rearwheel?

 

Hopefully flywheel.
Chevy Lover, if you want 400ftlbs at the rear wheels, you'll need a bit bigger of a cam... and overall combo. You'll need ~500ftlbs at the flywheel to hit that. But, at flywheel, you'll be pretty dern close. Your rear end might actually hold up for quite a while with that combo. I would recommend 3.54 or 3.73 (anyone second?)

 

im sorry i leave the computer on when i go to bed. i would like to put 400 hp-400 ft lbs to the ground.

 

what would u put 4 400ft lbs,thats still STREETABLE?

 

Actually I think it sounds like you have a pretty build there (particularly the new edelbrock intake its my intake of choice hands down). I dont know what your running for compression but I would hope it would be like 9.5 or better. However it will in no way meet your expectations for 400 hp/tq at the wheels. The thing about torque and hp is in a sense they are the same. I mean hp is just torque at a particular RPM. High hp motors just have their torque curves shifted into the high RPMs which results in what is known HP at the expence of low end torque. Now to get 400 hp at the wheels would mean about 500 hp at the flywheel. This is really pushing the abilities of a 350 and would in no way resemble something that would be driven on the street. The other problem is the mods it would take to get 500 hp would completely destroy your torque missing that goal entirely. The only way your going to get those sorts of numbers is by going with forced induction or a larger motor. Now lets talk for a moment about what your goals really are. How did you come to the conclusion of you want 400 hp/tq? More than likely because that sounds fast am I right? Lets be a little more realistic for a moment. What are your expectations for the car? Is this a fun daily driver or a competitive strip car? The difference is a street car spends most of its time in the low rpms so building a motor to match will make it feel faster and be more fun however your 1/4 mile times wont be as good. The reverse is also true a motor built for the high RPMs will have great times at the track but on the street will feel more sluggish due to the lower low end torque. This concept of building a motor to match your purpose i could go on all day about but why dont I give you a chance to speak up and let us know what you are really expecting from this car?

 

thank u 4 the insight. i want a car thats QUICK. my car is a daily driver.so i want syeetablity! but i want to stonp ricers,and dog mustangs,OLD AND NEW.i drive idel to 3000rpm unless a mustang pulls up.i have 3 carbs.holly 3310-750cfm,holly650dp,summit 600cfm worked over.my summit WAAAY out performs the other two idle-5000rpm.i need gears, posi,MAYBE torque converter.ive had people tell me to get a bigger cam.or call my cam a baby cam.but i dont want a low end dog.am i on the right track?

 

Well ok first where do you race the track (1/8th or 1/4) or the street (streetlight to streetlight or highway)? If were talking about short races like the 1/8th or streetlight to streetlight youll want to build up your low and mid range longer races like the 1/4 mile well want to build more high end. Now lets look at the competition most of these cars would be beat by a low 13 second 1/4 mile car would you agree? So depending on your cars weight (ill assume a worst case scenario at like 3600) I calculate youll need somewhere around 300 hp to be in that low 13 second range. Well shoot for 350 to be safe. Because all you need is 350 we can build up a tame 350 that would be great on the street lots of fun and still take out most of what you would ever encounter on the street. There is also the possibility for adding NOS so you can still have a great street motor and still have that extra punch in reserve when needed to take on the cars that run in the low 13s/12s. Sound like a fair plan to you? As far as your cam is concerned yes people will always tell you you need a bigger cam when in reality they just dont understand cam theory. That is certainly not a "baby" cam nothing too crazy but its a good cam cam for the street. Cams have to be matched to the rest of your build and that cam is a fairly decent match. I think it would better a slightly better match if it was maybe a tad bigger if you did go with the edelbrock manifold you mentioned but that will push your power band into more the 2-6k region which isnt bad but considering you run in the idle to 3 k region normally and your motor redlines at 5.5 k it has some waist that could be better put to use with some tamer parts like the ones you have currently. Really I think your current build is pretty decent all and all. The only improvement i might comment on is if you were willing to go fuel injected with a modified TPI set up we could achieve this performance level discussed earlier of around 350 hp but with the side benefit of big block type low end torque. Other than that though no real recommendations. I think because the motor is pretty much what were looking for your purpose or atleast what i understand your purpose to be I think we would be better off making improvements to the rest of the car to allow that motor to work to its highest potential. For example being that you have a car that was TPI with a slush box your rear gear ratio is probably pretty low numerically many came with 2.73s yuck! I think you would feel a fantastic jump in performance going say a 3.42 or even a 3.23 (unless you have one in which case you can leave it if you think that would be better for you they are not that bad). No more than a 3.42 though. Also time to look at the suspension, wheels and tires, weight ect. So give it some thought and let me know your thoughts on this matter are.

 

Also on the torque converter although this is another one of those people will tell you to run a huge stall converter the stock one isnt too bad for a motor like that. Im not sure what it is technically I'm guessing around 1600 but that would get you right into the bottom of your power band so its not to bad for the street. You might like having a slightly looser torque converter but I wouldn't recommend going beyond like 2k or so should you decided to go that route.

 

thank u. i realy appreciate your responces.my red line is about 6200-6500rpm i have lunati push rods,1.46-dual springs135LB SEAT 400LB OPEN.ive only run on the streets so far.can wait to take it to the track!car is 3450 with me in it.i need posi,and maybe gears.i say maybe,because if i stomp it i can burn out first three gears.it will break loose at 55mph.maybe the last guy put in gears.he put in a shift kit. i have been in lots of stock irocs and u can really tell the difference in mine. i bought it with tpi.it ran out of steam 4500rpm!

 

i read thay make a lot of heat.an prevent lock up.that means no 4th gear right? the hot cam is 1800-5800rpm great 4 air-gap rpm intake,but air gap might like a bigger carb right? what is a slush box. im guessing auto trans

 

Well keep in mind its not just the valve train that has to hold together at those RPMs. Yea sounds like posi would be pretty important lol. What are you running for tires? Yea the factory TPI is kinda lame on 350s with mods though it can build up into the 5.5 k region which is again considering the reline of a factory motor pretty good. Coupled with its incredible low end torque its my intake of choice for a fun car. Definitely not for everyone though.

 

Well heres the story on torque converters. When you have a high stall they dont lock up when your just putting around this slipping does generate a lot of heat. Now when I say this, this is again looking at cars with like 3k stall speeds so its not hard to see how they would have a problem considering like you most people spend their time below 3k lol. Further more our lock up is electronically controlled as well and i believe it locks up about 40 MPH anyways if you still have your comp in place. It does not effect the use of 4th gear though thats a separate thing all together. As far as the manifold is concerned I thought the edelbrocks intakes power band went up in to like the 6500 region but i might be mistaken on that in which case that cam might be a better match thought. As far as the carb is concerned this is another one of thoes cases where you have to trade off performance for fun. Like you noticed you liked the smaller of your 3 carbs which dosnt surprise me it would give a stronger lower (making the car feel faster) end better throttle response ect. I think you might want to try out the 650 you have assuming you still have it. On the dyno it would probably even yield a few more hp going with the 750 but again there is a trade off and on the street I don't think the trade off would be worth it. Really I think again trying to pick between the 3 just on feel I think you would go back to the 600 but I think the 650 would be a good compromise for performances sake but as always the choice is yours. If you still have them try them out see how you like them.

 

Oh and yes a slush box is just an auto trans.

 

im going to buy 20in.back 18in.front iroc rims.so for now i run 255 el-cheapos.bottom is totaly rebuilt.if something gave at 6500rpm,it would be the only stock part from oil pan to air cleaner.THE LIFTERS IMO.im 35yr, im trying to build a FAST grate running good sounding car.it has taken me 2yrs to get this far.what car could i get a good posi from.someone told me to get an 8.8 out a explorer.thats 4.10 gear right? i might NEEEVER STOP SPINNING

 

Have u looked at the summit carb?its a old holly.holly makes them.I LOVE IT.very simple great permformimg carb. ive put all my carbs on.all new carb. thats another story.the 650double pumper mech. second. has a bad takeoff.idle-2500 it sucks.comes on like bat out of hell around3500.that dang carb almost made me crash in the rain! ive worked my summit carb over. it takes holly after market parts.i put in bigger jets,50cc accelerator pump.

 

how do i tell i have a new post?is there something i push?

 

Well to be honest I'm not sure what the explorers came with for a gear ratio but you dont want to go that high anyways. First gear would basically not even exist and you would be singing along pretty good on the highway even with an over drive. It wouldn't be too bad but i just think its a bit too much just my take on it though. Now as im sure you know you wouldnt be able to just take the posi from the ford 8.8 you would have to swap the whole axle if you were going to go that way and that would take a good bit of fabrication to pull off although it has been done a few times. My biggest concern is strength you've got a pretty stout motor so heres what i see for commonly available choice. The factory 10 bolts had a posi option with a wide variety of gear ratios but were pretty weak so thats probably not a good choice. The factory 9 bolt which may be what you have in place now was pretty decent. I dont know what they were rated for but they have been used behind some pretty hot motors and help up fine. They are kinda rare though so parts are hard to find and gear ratios are limited to like 2.73s 3.23 and 3.42s or something like that. Also the differential wasnt the greatest by design would be burnt up by doing burnouts on like wet pavement. Those are about the only factory bolt in options you have. Beyond that you could go to a ford 8.8 which are pretty tough would need some fab work though. Not sure what ratios these had from the factory but since the mustangs used these I assume they have many flavors. Aftermarket options are like the ford 9 inch (which is the strongest and my personal favorite) and the chevy 12 bolt. Both are made to be bolt in pieces from aftermarket companies and either would be strong enough and offer a wide range of gear ratios. May be a good opportunity to go to disk brakes as well.

 

There is a way to set up email notifications. Its been so long though I cant remember exactly how. I would assume it would be in the user control panel somewhere though.

 

to be honest with you I would like to put a posi and stonger parts in my 7.65.with 3.42

 

Yea summit is notorious for that sort of thing. They dont make their own parts but have other well known companies do it for them with a summit name on the package at a lower price. I cant blame them though why reinvent the wheel? Holleys were great carbs. For future reference though you may want to stick with vacuum secondaries instead of mechanical. I know i ran probably that same carb an old holley 650 (still have it) with mechanical secondaries so I know exactly how you feel lol.

 

Well there are ways to beef them up somewhat. Unfortunately there is an inherent limit on what it will take considering the ring gear size. But hey they are cheap and pleantiful you could try it out they did come with posi 3.42s and disk brakes on top of it. With some work if your nice to it it may last the life of the car and if not oh well you tried right? The 4th gen camaros use nearly the same 10 bolt rear behind 300 + hp ls1s and had a great differential in some of them. That would be an almost bolt in replacement.

 

thats been my thought the hole time.grab one out a fourth gen. and like u said disc brakes. u r knowledgable. jump over to summit tell me what u think about the carb please.it really flows 675cfm,i love it

 

Yea thats definitely a holley lol. Have to love summit its the walmart of high performance lol. They are a great carb all and all. Lots of aftermarket support. Once you get the details picked out with vacuum or mechanical secondaries what type choke and all you really cant go wrong them. I know ive always had good luck. My old charger and road runner still use them and i used to use one on my camaro till i went to a 2 x 4bbl set up.

 

i was looking at an air gap 2x4bbl. and buy arother summit. too much right? but being vac.sec?

 

Yea i would tend to shy away from the edelbrock 2x4bbl set up it looks cool but performance wise you would be better off with their air gap RPM and a single carb. Besides the holleys wouldn't work on it anyways due to clearance issues. You would have to use like an edelbrock carb on it or something equivalent.

 

what clearance?what r u using

 

I mean clearance between the carbs. Even mounted sideways i dont believe you would have the clearance to run 2 holleys at least i should say on edelbrocks manifold others you could though. On my 2x 4bbl set up i run 2 edelbrocks and even that is a pain as the mixture screws on the second carb are pretty close to the carb in front of it making adjustment difficult lol.

 

would i create enough vacume to open 8

 

Oh yea it would work just fine in that respect. You can always change the springs that activate the secondaries anyways. Besides the front 2 barrels are mechanically operated only the rear one that are vacuum operated.

 

u have helped me so much.also gave me a lot to think about.im 35 an i just enrolled in college the be a mechanic.the more i do to my iroc the more i like it.in this economy i think im better off working 4 me.hey.whats you take on the procomp heads. my 190cc TOTALY CRUSH my ported,shaved,3angle.z-28 comp springed L98 HEADS.maybe im lucky

 

Yea its a very tough economy right now. Although getting into a trade as an automotive technician is not a bad idea. They cant ship your job overseas lol.

Anyways on the head theres really not much I can say as I havnt seen any flow data on thoes heads yet. The thing about heads is although people pretty much exclusively talk flow numbers thats only part of what makes a good head. See a motor is only going to take in as much air as it required to fill the cylinders. So in the low RPMs both factory heads and high performance 220 cc heads will both have the same flow rate as determined by the motor displacement and the RPM. However there is one big difference and that is air velocity. The air in the stock heads will be moving much faster which will lead to better atomization which will yield more performance at that RPM better fuel economy and throttle response so on and so forth. However in the high end this is where max flow numbers start to really matter. The cylinder can only generate so much vacuum to force the air in and due to the limited time to take air in the stock head would not be able to flow air in fast enough to effectively fill the cylinder. This is where the larger 220s would have the edge. One important thing to take from that though and what really determins the quality of the head is how much air flow can they get out of a certain size runner? I mean 2 heads that had the same flow rates but one was a 180 and the other was a 220 cc setup although they have the same max flow the 180s would be far superior by virtue of the higher air velocities. This is why AFR heads are treated as if they were made of gold they are very well done heads and flow great for their runner size. This is also why vortec heads are so popular. Not only are they cheap and plentiful these heads are just designed differently from your typical SBC head and their design (based of the LT1 head technology) inherently allows it to flow better from a given size runner. Factory versions can compete with aftermarket heads and high performance bowtie vortecs are just hard to beat for their performance and cost. Another thing to conciser the cam and how it effects flow rates. Although 2 heads may have the same size runner and same flow rates at .5 lift or whatever one head may flow better than the other in the lower cam lifts which will allow for a higher total amount of air flowed into the motor when it comes to a real world situation. So as you can see there is tons to it lol.

 

Hey man your posts are great. You have really helped me with a lot of my decision making. I will be going to perfomer rpm or air gap for sure. I don't know which yet as far as the heads are concerned there is a big write-up on chevy high performance Chump Change Challenge but I know that @500lift flow is 254 it is funny you wrote what you wrote about velocity. Because that is why I picked 190cc over 210cc they were both the same price, but I picked 190 because my motor is 355. I felt 210 was more 383+. I felt 210 would kill my low end and thats where I have fun. I have also decided to keep my lt4 hot cam. I love its street ability. I hate sending you to other sites to look at things because I see how people put those dashes on their threads to go straight to it, but I am barely computer literate and can't type. So thats why it takes so long for me to respond. Sorry.

 

Well im glad I could be of service. Also its no big deal sending me around to different website or taking your time to respond. It takes 10 seconds to type in a web address and whenever you respond ill get an notification by email so Ill know to check out the thread. No rush lol.

It was a good choice not going with the 210s. Sure they would flow better but it would hurt your bottom end (due to the low air velocities) and i think your top end gains would have been marginal as it would flow more than a 350 built up like yours could make use of. Basically a lot of sacrifice for virtually nothing in return so it was a good call.

On the intake the only thing I would watch out for is if you are considering going with new heads I wouldnt get the intake just yet. Reason is I think you would be very impressed to see what a good set of vortecs would do and the intake manifolds for vortec heads are different than your classic chevy heads. I can virtually guarantee that in chevys chump change builds they will be talking a lot about vortecs. To demonstrate why ive got some info on what the bowtie vortec heads would flow.

Now you say your 190 cc flows 253 at .5. A botie vortech head with the small 175 cc intake runner flows 251 at .5 according to super chevy. So basically you could improve your bottom end and not sacrifice your top end. Not to mention these heads are also cheap and can be picked up from your local chevy dealer. Now granted I dont have the full chart to really make a good comparison of the 2 heads but something to think about.

 

superchevy.com chump change challenge.that is the site. man as tight as money is these day ,mustangs would have to start killing me for me to spring 4 another pair of heads! but i have a 81 im about to start after this.please read that as it may help u help me.i dont know,rpm, or air gap for cam and carb that i have???

 

Yea it was a pretty stout build. From what they showed it seems like it had a very flat torque curve. Although I did find it a little interesting the started the data at 3k RPMs. Given the parts they used like the 282hr cam I'm sort of not surprised though as i dont think the low end would have been something they would want to advertise lol. I think they could have dont a bit better with it and i wish they showed more low end data to give a true picture of the results but on a $1000 budget and restricted on time I cant say I could have done much better lol.

As far as the intake goes either way I think you would be happy although I dont think you would notice much of a difference going with the standard RPM manifold over what you currently have. The RPM air gap on the other hand is a little hotter than the standard RPM manifold. I ran an air gap manifold and I loved it. However, I will caution you on one thing. If you live in a colder climate as I do the runners can get a bit more chilled than you would like which makes driveability suffer more so than what would be expected of any carb set up at least till the car gets warmed up.

 

man i wish it was cooler!i had to take the family to the zoo today 103f.hows that for cool.i live in lower sc.well ill have to hunt 4 a cowl 4 a good price.question, how can it be hotter with same rpm? im guessing cooler charge .i was told air gap has old runner tech. and rpm has newwer computer bent tech.do u think the holly 670cfm street avenger would $370 OUT PERFORM the summit carb. cause something in my head is telling air gap is doing to want more carb

 

Lol well hey I would take 103 any day over shoveling snow and sliding all around when i have to drive around lol. For the manifold the RPM advertisements are more of a guideline than a hard and fast rule. The air gap manifold is a little taller (sort of like a tamed down victory jr manifold for the street) and separated runners creating the air gap I always found made a good bit of difference. When it was cold out it made a little too big a difference actually lol. I hadnt heard anything about design of the runners though so you may have a valid point there. Something to look deeper into i guess. For the carb yea I bet the 670 would out perform the 600 on the dyno. However again like the cylinder heads the motor is only going to draw in what it needs so the 600 would feel more peppy and have more throttle responce in the lower end. Becides you could always try out the 600 and see how you like it. You can always upgrade later down the road.

 

One thing i think i should rephrase is on the manifold as i dont think i was really clear on it. When i say its hotter even though it has the same advertised RPM band as the standard RPM manifold the air gap does better within that band than the standard RPM manifold.

 

Actually ya know what after comparing the RPM to the AIR gap RPM there is no difference in height according to their web site. Seems aside from the air gap design they seem to be basically identical. Though I havnt come across anything on the port design though. Still looking into that.

 

when i look at the two the performance looks the same.thing is sbc doesnt like heat,so people running 180-195 therm.could be helped buy the cooler air gap rpm.people running 160therm.might like the performer rpm.i dont know just guessing.i will say this performer rpm cost $140. rpm air gap $210.now the pro.products air gap rpm knock off is 150 shipped.the intake i have is pro.products an it works great

 

Yea the professional products version looks to be pretty much the same. On their website they dont seem to give any dimentions for the manifold or the runners so its hard to say for sure. However it probably doesn't matter even if they weren't identical I doubt there would be much of a difference performance wise. Ive always had good luck with edelbroc so i havnt tried one of their manifolds but if youve had good luck with them why not save a few bucks?