CrazyHawaiian

Well I didnt really know where to post this considering I wont be swapping my motor, but I had a question about building up a L98.

After riding in my friends Z06 I'm sold on the top end street car type of setup. His LS6 launched pretty good, but the engine really screams on the top end. It was really fun on the highway!!

Because of that experience, I want to build my motor for top end power. I want the car to pull hard to 6500 rpm like a LS6. Right now I have a completely stock L98 and a Vortech S-Trim (V1) blower @ 6 psi. I can feel the power drop off around 4500 rpm.

I am in the process of planning a motor rebuild (gotta do rings anyway) and I am looking for info on what engine components I can use that will give me more top end power. I know the intake design has alot to do with it, so thats the first thing I looked into. I've decided to go with a Holley StealthRam intake instead of the TPI intake. I'll also need a bigger TB. That seems like a good choice for top end power. Do you guys agree? As for the ECM, I'm doing the 749 Sy/Ty swap and I'll be burning custom chips so the tuning wont be an issue.

I am looking for info on what I should do with the motor itself (heads and cam, etc) to make alot of top end power. I'm thinking about lowering the compression to 8.5:1 and turning up the boost. That would give me more top end power right? The blower can support up to 20 psi intercooled, I can tune the ECM for 20 psi, and I'm planning to build the motor to handle 20 psi.

I was wondering if you guys could give me any tips on what heads or cam to use? Or if anyone has a motor built for top end power with a 350 block and crank, can you tell me what components you used? Or anything I'm leaving out?

Drivetrain will be a T56 and a 10 bolt with upgraded gearing. Car wont be used for dragracing and will never run slicks, so wont have to worry about hard launching. I want to build this one to have some top end fun (other Camaro will be the torque machine). I want to beat my friends Z06 on the freeway. Curious what you guys would sudgest. Thanks!!

1991tealRSt-topGuy

start off by getting rid of the TPI

you should notice a big improvement with a better manifold


next some better flowing heads and a cam with more duration


lastly compliment all this with a custom PROM and a higher stall torque converter

1991tealRSt-topGuy

sorry just noticed you said T56


just dont ask the stock bottom end to spin too high

maybe like 6500 RPM max

QwkTrip

iTrader: (22)

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CrazyHawaiian

Very impressive results with that Vette considering like you said alot of the stock components were used. I dont know the actual limits of the S-Trim V1, because I'm running the same 9 psi pully you're running (however I only see 6 psi). Here is how Vortech rates it:

VORTECH V-1 S-TRIM SUPERCHARGER
The industry standard supercharger

Straight cut spur gear
Fits engines up to 680 horsepower
Maximum airflow: 1,000 CFM *
Maximum boost pressure: 20 PSI *
Maximum impeller speed: 50,000 RPM
Adiabatic efficiency: 72% **
Available with straight or curved discharge and clockwise or counterclockwise rotation

* Flow and boost ratings are based upon efficiency. All Vortech superchargers can exceed these ratings but they cannot perform efficiently above these ratings. Vortech uses an efficiency rating of 60% and above as the approximate minimum usefull range.
** Efficiency shown is for straight discharge. Curved discharge is 1-2% lower.

So that kind of gives me hope. I know for sure boosting over 1 bar (14.5 psi) will require an intercooler. So thats something I am planning as well (ATI 3rd Gen Twin intercooler Setup, thanks Willie!). Tuning will also be a big issue, but I'll be taking care of that with a 749 Sy/Ty ECM swap and custom chips.

Well I have to say reading about your Vette I'm pretty excited. If you could push that much power with the stock but modified heads, crank, cam, etc then I should be able to reach my goal using aftermarket parts. I'm budgeting around $6k for the motor buildup itself. I plan to do the bottom and top end. I wont be pushing high boost untill I'm sure the drivetrain can handle it.

Any other people out there using aftermarket parts (heads, cam, etc) to produce alot of top end power?

J's T/A

iTrader: (2)

Whatever you decide, make a budget... to get the top end you may end up spending more than the LS6 that you enjoyed so much..

Keep up the drifting your car is pretty kewl.

CrazyHawaiian

Hey I hear ya! Selling one of my project trucks (97 S10) so I can fix up the 3rd gens. Had to wait before I started doing stuff because I had to refinance my house. But now thats done and I'll have about $11K to fix up both my 3rd gens and my house (appliances).

I wont be doing the motor on the 91 Z right away, but I'm trying to get the plan together. Before I do the motor I want to redo the cooling system as well as the brakes. Want to make sure the car will be able to support these kinds of mods. My drivetrain will be a weak link for a while, so I'll be running low boost. But the fact is that the rings are going in the L98 and it has 113k miles (35k miles boosted). So pretty soon its going to need the rebuild anyway. Might as well go all out while its out of the car.

To be honest I think my 90 RS drift car will be completed before the 91 Z. My G/F's dad and I will be doing all the work (motor swap, interior, suspension, and paint) so I'll be saving alot of $$. I also got mad deals on all the parts (got everything for under $2k). Cant wait to get it back on the track with a 350, full suspension, gutted interior with a cage, the ROH ZS's, and new paint.

Since the 91 Z is my daily driver (aka needs to be very reliable) I have a professional mechanic thats a family friend doing all the work. I wanted to read about some other peoples setups before I get with him to do the motor. From doing reading I've realized that I'm going to need a strong bottom end (crank that can spin to 6500 reliably), aftermarket heads for better top end flow, a cam with longer duration, a different intake setup with more top end power, and good tuning to reach my goal. Motor itself should be around $6k. Intake and Injectors another $1k. Total cost of everything well over $10k but I have a long time to complete this project. And considering all projects cost more than you initially think, I think it will take $15k to get my 91Z where I want it.

CrazyHawaiian

BTW, thks for the tips 1991tealRSt-topGuy.

wm_sorg

You will definetely need a super ram intake set up. Next will be hard core porting and polishing to get thise heads to breathe. I would consider going to bigger valves as well. Higher duration is good, but you also want high lift. Springs and pushrods also a must.

Then comes the fuel system. More pressure bigger injectors, etc.

I like your idea of lowering compression and raising boost. I am surprised the L98 does not make top end power with that on top of it.

If you do this right it will not be cheap. I would guess you will be in the range of 3500-4000 dollars. I would suspect at least 1500 will be for the heads.

You may want to consider an LS1 sawp as an alternative.

iroc22

You should try and find the specs on the LS6 cam and LS6 head flow numbers and match them. Although the LS6 is an entirely different small block, I'm sure matching the specs will yield similar results (but that blower will bump of the torque a lot). The LS6 I bet could definitely hit 7000rpm easily but the fuel shuts off at 6550rpm

J's T/A

iTrader: (2)

There are a few ways to go at it.. but you are right, go for the brakes first.. I think it would be cool just to plant an LS6 smack in there, with some head work on that.. vipers may even have to think twice...

Budgeting is good, I am pretty burned by my current project.. lets just say it is over 10k right now.. I tried to be disciplined with it but it snowballed, or avalanched, oh well..

SFX099

Probably easier and possibly cheaper you could get a 400 block and build a 377 they rev higher than a 350 due to the 400 being destroked. I built one in desktop dyno a while back with Vortec fast burn heads, Performer RPM air-gap intake, 750 carb and a hydrolic cam that made 483hp@6000rpm. I didnt really get out of the powerband until around 6800rpm. That could just work better than a 350.

ME Leigh

How about a LS6 swap they are only $7000, for a complete motor, minus ECM. http://www.paceparts.com/product.asp...&1=241&3=56136

CrazyHawaiian

Hey thanks for all the replies everyone. I think a LS1/LS6 swap would be awesome but I dont think it would be a good choice for me because of two reasons. The first reason is that the LS1/6 motors need alot of work to reliably handle the kind of power I'm planning to make. 600+ hp @ 1bar+ boost is alot of abuse on the engine. A stock LS1/6 would need a rebuild to handle it. Plus the blower I already have wouldn't fit on the LS1/6. I do alot of reading on LS1.com and most of the guys over there with blown or turbo LS1/6 motors have problems once they boost over 12 psi. Most guys will rebuild the motor with the 5.4ltr truck block and the LS1/6 heads. The LS1/6 would be a great choice if I wanted N/A power, but since I'm boosting I think it would be cheaper in the long run to just stick with what I have and make it strong. The second reason I dont think it would be good is because of the swap itself. When you do a LS1 swap usually you have to relocate alot of the engine components and some you have to give up. By sticking with the L98 and building it up, I wont have to relocate anything (power steering or brake master cylinder) and I can keep some creature comforts (like A/C).

The 400 block destroked to a 377 sounds like an interesting idea. I've seen alot of posts about this lately. This is something I'll definately look into but destroking just dosnt make sense to me. If I did go with a 400 block I'd probably stick with the 400 and go for torque. But when it comes time to spend the $$, I'll definately compare the 377 idea to the 350. I think the 350 will be more than enough since I'm boosting (377 would be good N/A top end power).

I think iroc22 had a really good idea. I'm trying to get the powerband characteristics of the LS6, so I should look into how its setup. I didnt find any head flow numbers yet, but I did find the cam info:

Camshaft 12565308 (hydraulic roller):
Gross Lift (.550” I / .550” E.)
Duration @ .050 (204 I / 218 E).

One of our users here already has a setup that I really like. I think I'm going to be reading up on the parts he used and go from there to decide what would work for me. The user is bbunting and I give him alot of props ( :hail: bbunting). His car is putting out 649 RWHP 580 RWTQE @ 12 psi on pump gas. His components are: 393 CI, Vortech YS Trim w cogs, 12 lbs. boost, custom Spearco intercooler, Mondo, Stealth Ram ported to FP 1206, ASM 1300 CFM TB, Accel DFI,72lb/hr MSD injectors, Aeromotive 11104 pump, Summit alum 15 gal cell, Dart Pro 1's 230 CC,custom solid roller.

After reading I think the hardest part of reaching this goal as far as the supercharger goes won't be the intercooler, won't be the tuning, hardest part will be getting the belt to push 18-20 psi (dont know if it can do it). Maybe 12 psi will be the max I can run

camarojoe

Hey CrazyHawaiian,

This is off topic but I was wondering if the paint on your 91 is the same sunset orange like the newer f-bodies have? Either way I love the color on the car and I'm thinking about going with the sunset color in the near future.

CrazyHawaiian

No worries man. The paint is 2002 GM Sunset Orange Metallic. I'm not sure if they offer it on the newer 4th gens. The color is really growing on me. Thanks for the compliments. Hopefully soon the car will be able to back up an orange paintjob. heheh!!

Black363IROCZ

get a 363, top end matches with BPU supras are no problem

89firechicken

biuld a d-stroker those are very good top end motors use a 400 block with a 3.75 crank, afr heads, super ram, with your s-trim backed by a t-56 and a 3.42 gear and you would be surprised on how that winds up and your top speed would be impressive. you may want to jack some ri(ers wing to put on your car because unlike them you'll need it.

Black363IROCZ

^this is true, a 377 for instance, one of the sickest small blocks out there. sacrifice a little, I mean very little low end grunt, for a high end rush that'd embarrass an LS6 with a 150 shot!

89firechicken

what i wanted to do was but a 327 crank in a 400 block which would make about 350 ci. and rev like motorcycle but my car weighs way to much for the loss of torque. mabey if i get my hands on a vega i'll use that combo but untill now the bird gets a 377.

Black363IROCZ

a 377 is basically a big bore, high revving 350, can never go wrong with that. I went with a 363 cause I had a 350 block, not a 400, but I'd love a 377!

89firechicken

well it's kinda like a high reving 350. but when you down stroke a motor like that you also reduce friction on the cylinder wall which increases in the life span. think of the 377 like a big brother of the 302 in the 69 camaro rs/ss

Black363IROCZ

yup, leave it to GM to do a 302 right they should revive that motor. it was a beast

Air_Adam

Yup... want a high winding engine? Build a 302... in '69 they were good for 8000 rpm and often, much more.

SLP IROC-Z

iTrader: (1)

holley stealth ram, mini ram or even a modded LT4 intake manifold. and a nice cam to compliment it, u should be getting some topend power there. i know the tpi doesnt make much power after 4500, i still have to shift at 5k but i mean the car goes just as good on the highway as it does on the street all u gotta do is keep it in the power band, IE; shift to the next gear, u said u had a t56 right, shouldnt be to hard to keep in the meat of the poewr band. i have no problem with my t5. i can go from 60mph to 130mph real quick