neat

I'm getting ready to buy parts for the build up of my 1991 Corvette.

I came from the LS1 camp over to a Gen II expecting lower initial HP numbers, but once you started modding I figured a Gen II would have no problem laying down power numbers near that of their LS1 brethren. After a bunch of reading on www.corvetteforum.com and www.thirdgen.org I noticed that no L98 based engine really seem to put out the power. I can count the number of 425+ RWHP L98's that I've seen on one hand, and none of them were stock displacement.

I really don't see why an L98 with a short runner style intake like the mini-ram can't make the numbers. Maybe you guys know of a combo capable of laying down 425-450 RWHP that could go for 40,000 miles between rebuilds?

The goal is 425 RWHP NA, decent fuel economy (18+ MPG on 6th gear on the freeway), and strong enough internal components that will with stand a 200 HP shot of nitrous.

To me, coming from the LS1 crowd, those numbers seem entirely reasonable. To the other Gen II owners I've spoken with, those numbers are ridiculously high, and they seem to think I'll need gold plated cryptonium parts that cost more than a house.

What do you guys think?

TwoFast4Lv

iTrader: (8)

the biggest key will be good heads and a Stealth ram intake I see 400RWHP no problems

TransAm12sec

There are some people one www.thirdgen.org that may be able to help you out.

With the stock cubes, you're going to reach the limit with a nice set of heads and a cam.

neat

A stealth ram won't clear the hood on my vette, so it's out.

The only guy on 3GO I found who was making the power was Matt87GTA. He dyno'd upper 400's with a solid roller 383. Have anyone specifically in mind on 3GO I should seek out?

YenkoST

iTrader: (10)

There are more people than just a few making the 400+ power numbers. However, if you are talking NA then that's a different story. One setup that is making those numbers is a 383 with a SuperRam making 510 ft lbs and 420 hp. That's durn impressive in my opinion for a NA engine. Me personally, I don't know how much I am making but I have a 383, AFR heads, Stealth Ram and its fun to drive and I know with a 100 shot I will easily make 425rwhp. Just depends if you are talking NA or FI. NA you will have to go bigger cubes, different intake/runner system, cam, and heads. Some people with a 350 are making 350rwhp so its very possible.

However, L98 engines aren't the dyno king engines but they are impressive on the track for example, a 383, AFR head, 219/219 cam, SuperRam system will run 11s all day long but will only make about 350rwhp. These engines live on torque in the lower to mid-range, where the LS1 is all about hp and top end. And they're better cams out there for more hp/tq.

91Z28

My combo better make at least 410rwhp. I just ordered a set of heads that'll flow 310cfm@.600. I'll be using them on my zz4 shortblock with the stealth ram and Comp cams 280xfi cam 230/236 .594/.588 113 LSA with 1.65rr (comp 1100 series hi-tech stainless). I think 425rwhp is easily done with a 383 like was said above. I've seen a few 525-550hp solid roller 383 builds. NA of course.

TwoFast4Lv

iTrader: (8)

BTW Another company makes a top for the Stealth ram that fits the C-4

1bdbrd

iTrader: (12)

i think the problem with a big majority of heads and cam setups on TGO is the combination used. most are extremely budget. meaning stock vortec truck heads with a small cam designed for a TPI setup. hell a set of stock vortecs, LT4 hot cam and a modded tpi will make 300+rwhp with HUGE amounts of torque. most also dont want to give up low end torque that the TPI gives them.

me personally im hoping for 420-430rwhp with my heads and cam setup. i should realistically see no less than 390rwhp. im going to run a converted lt1 intake, cc306 (230/244 .544/.576 112LSA) cam with ported trick flow heads that im hopin will come close to 300cfm and pairing that with a t56. that should make a relatively fast car. im worried how long the stock bottom end will take 6500 but well find out.

btw, car is a 91 trans am.

91Z28

We have similar goals. I ordered a set of trick flow bare castings with stg II porting from a sponsor here, www.portpros.com. They should be in the 310cfm range, so I'll be getting my stealth ram ported to support that. I noted the cam I'm using above, and I'll also be using a T56. I also have questions about my stock bottom end living, especially if peak power ends up being around 6300 or something crazy. Ideally I'll make peak power at 6100 and shift at 6500, but we'll see. Most people tell me the ZZ4 shortblock is pretty stout, so here's hoping.

91Z28

I just looked up some builds in a SBC book I have, and it has a solid roller 11:1 385 (.040 over) making 550hp NA, here are some details

TFS 215cc heads (I'm sure AFR 210s or the new Patriot 215cc heads will work just as well)

Solid Roller 246/246 .630/.630 110 LSA

Super Vic intake, in your case I'd use the miniram

Long tube headers, 1 3/4" (For this hp range 1 7/8" might be better)

Port those heads and use 1 7/8" heades and you'd definitely see 550 at the crank.

TwoFast4Lv

iTrader: (8)

I Spun my stock LT1 bottom end(basicly the same as TPI) to 7k for 20K miles

Biggest thing is to make SURE to valve train is up to par and CHECK it often!

Good luck!

OH yeah still isn't as easy as many think to get much over the 420 mark with out some work.

91Z28

My valvetrain should be good, I splurged on pretty much everything I could think of. I had planned on using Hydra Rev as well for insurance, but you steered me clear of that with your thread.

TwoFast4Lv

iTrader: (8)

Glad I helped you out there! I am just getting the engine back together after that. Nice set of Morel link bars in there now

BTW any want a AFR Hydra rev kit and a few sets of Comp "R" lifters?

91Z28

LOL, the notorious Comp "R" lifters. I stayed with the stock ones, I heard they are pretty good actually. Screw AFR, I figure with Comp 1100 series Hi-Tech Stainless Rocker arms (1.65), comp 918s, titanium retainers, hardened pushrods (of the proper length) I should be ok to see 6600 without valve float.

1bdbrd

iTrader: (12)

seriously bro i cant count the number of times ive watched the video of your car. i love everything about it. its actually inspired me in a few ways as well. PLEASE keep me updated on the progress of your car as it will be a bit before i get mine going. right now all i have is the cam.

as far as more details, ive decided to go with the standard TFS 23° heads which will be ported and polished by a local guy (non-sponsor so i cant post his site) and he said with just basic work i should see around 280-290 at .550" lift. which for traditional 23° sbc heads thats DAMN good IMO. im going to run a set of comp 987 dual springs with titainium retainers per a guy on TGO. i was going to run some 918s like you but the 987s are half the price and IMO a little better insurance as well. im going to pick up a stock set of LT1 lifters as they are actually very strong and less than 85 bucks from GMPP according to cz28. im going with custom length hardened comp pushrods and a set of comp pro mag 1.6 rockers. im also thinking about a crane stud girdle just for a little extra safe (and some under valve cover bling... ). ill have an lt1 intake i MIGHT at the very least have gasket matched but i may opt out before i throw it on and have it ported for a 58mm tb as well as ported in the runners as well. followed up by a new msd billet (unless i find a better or just as good cheaper one) dist., msd 6al (i need the rev limiter for this), a new high flow aluminum water pump from Jegs and a cloyes true double roller. and ill have the same 2210 hooker long tubes you have.

like i said, with this i expect 390 atleast. but if the bench racing numbers ive pulled up are correct, i might get as much as 430rwhp. and like you i want to limit it to 6500. i have a stock L98 bottom end and not even a zz4 bottom end like you. you should be fine. ive never heard of pistons failing because of rpms, and you have a forged steel crank and PM lt1 rods which ive been told are VERY beefy.

if money plays out i might slap on a hidden 100-150 shot just for more fun. and when it finally goes im in a toss up between a built ls1 with a procharger and lots of boost or a 408 sbc with a big cam some 18° heads and a 200 dual stage. either of those should get the job done nicely i think...

91Z28

I went with the 918s since they are lighter, I know they are good to .600 lift and I'll be awful close (.594/.588) but I may shim them just to get that extra 10lbs seat pressure just to be safe. Not to mention I found out that is the standard spring portpros uses, I paid 1899 and got ready to bolt on heads that will flow over 300cfm and have 918s and titianium retianers. A good deal I think. I was thinking about spraying 150 on top of this, but I don't think the LT1 pistons (which is what the zz4 uses) would like 400+rwhp and then a 150 shot up to 6600. I know the crank/rods are pretty stout, but the bearings I'm not so sure about. I've been told by several people that I'd notice no increase in performance stepping up to an MSD ignition, so I'm sticking with the HEI. I already got the cloyes double roller and a two piece timing cover. I pretty much have everything (heads should come in this week) except the fuel pump/lines and 12 bolt, then its time to get to work. Tuning is going to suck....

1bdbrd

iTrader: (12)

ya that was the big reason i wanted the 918s as well. but ive been told 987s with ti retainers and such will be pretty similar in weight but at a cheaper price. im thinkin ill have around 1600 or so in my heads which is more than a standard set of afrs but i wont have to wait on them like i would the afrs. i figured there really wouldnt be much of a change with the msd over the HEI but the real reason im buyin it is for the rev limiter. what timing cover did you go with? i was thinking about a two piece but i dont know if its really worth it unless they are about the same price. im goin to stick in some strong pieces into the rear end when i get the t56 and im not gonna be too rough with it. im hopin that will last a while as im going to redo the rest of the car as well.

and your right, tuning is going to suck. im gonna be pickin up a cable soon for mine as well as the craig moates ostrich. and im gonna tune it with tunerPRO, so hopefully it wont be too bad as no one around here really tunes TPI cars unfortunately.

91Z28

I got a proform 2 piece timing cover from summit for 52$

1989GTA

On the 3rd Gen board VincentZ28 is at the 373RWHP mark and 404RWTQ with his 355 and an M6. Hi expects to pass the 400rwhp mark with his next round of mods. By the way he is using a Superram that is for the Corvette. The plenum is shorter in height. He also has stock Trickflow heads with the CNC option.

Me, I'm only at the 330RWHP mark with my 350. With my next round of mods I hope to up that quite abit. DynoSim has me way up there in HP but we will see. I believe that 400RWHP number will be broken this year with a 355 L98. Lot of good cams and heads on the market these days.

1bdbrd

iTrader: (12)

i agree. im hoping this is the year people start making these cars fast and stop trying to make diesel like low end torque.

desktop dyno puts me at about 500 crank. heres hopin its right!