I have a 1998 6-speed Z-51 Vette with ~13K miles

I don’t want drivability issues like surging, bucking, high idle etc. I want it to have enough low end torque to not have a problem cruising down the highway at 1400-1700 rpm in 6th. I don’t want to be revving the hell out of the engine…6200-6500 MAX but wouldn’t mind keeping at 6000rpm and under. I want reliability and not have to worry about the valve train much more than you would stock. For example, I don’t want to be changing springs every 20K miles. This car will see 90% of it’s time on the street with the strip maybe a few times a summer.

Supporting mod that will be going on with the H/C swap will be American Racing LT headers, 10% - 25% UD pulley, dual cone intake, possibly an LS6 intake manifold and a dyno tune. I would like to shoot for over 400RWHP and would be very very happy with 425 RWHP area!

Now what I’m leaning towards from all my reading/research online.

Heads:
I would like to get some Patriot heads. But I’m not sure which would be best for my purpose? Would the LS6 style or the 5.3’s be better for me? Would the stage 3’s flow to much for me and slow down the velocities and kill my low end torque? Someone please tell me which patriot heads would be best for my needs and why? I have no problem running 93 in the car so would it be ok to go with 59cc heads and up the SCR for a little extra kick and better efficency? I realize I’ll have to watch out for my DCR depending on my cam choice.

Cam:
I’m leaning towards a TR224 because I’ve read several times that it is a proven good performer for a DD. But I’m also open to others if they can still be mild mannered down low and not have to rev the hell out of them to get into the power. A 224/224, 226/226, 228/228 or any combinations of them? I’m pretty sure I want to stay below the 230’s. Don’t get me wrong, I’m not looking for a car that seems 100% stock but has 100+ more HP at the wheels. I like a car to sound like it’s a little nasty and when you’re in it to perform…but in my vette I don’t want it to sound and act like a purpose built strip car. Absolutely no surging and bucking or not being able to cruse at 70 in comfort. I guess I want the best of both worlds and I want reliability. I don’t want to be pulling it apart every winter. But I’m not and ‘old man’, I’m 28 and if anything I’m probably making myself sound more conservative about this than I really am. I want it to be a little ‘nasty’ sounding when I’m on it but not feel like I’m driving a drag car around!

I’ve been driving myself nuts reading and reading for a couple weeks on heads and cams and just find myself jumping back and forth between different setups.

Help please!
Aero

 

I would say some stock valves LS6 heads and a 224 - 228 cam would get you to the 410 - 425 RWHP range. If you can swing it, look into a torquer2 or torquer3 sized cam. The drivability isnt all that different. Run enough compression and you wont lose all your low end. With a spot on tune, you can have very good drivability, yet the cam will still sound pretty stout. I drove an f13 and a T2 cam around daily for 2 years. I almost wish I went bigger.

 

Try to keep your overlap under 4 degrees at .050" for happy motoring. Once you get above 6 degrees, the streetability starts to fade pretty quick and you'll need a more comprehensive tune to retain your street manners.

Whatever heads you buy, aim for at least 11.0:1 static compression ratio. With stock head gaskets, you'll need around a 61cc combustion chamber. To keep your rev limiter below 6200, you'll want your power to peak around 5900 rpm. This means you'll want an intake valve closing point around 38-39 degrees ABDC at .050". With excellent exhaust paired with an LS6 intake, you'll get very balanced power delivery with a single pattern cam or no more than a 2 degree split. To enhance spring life, you should stick with Comp XE high lift lobes and not XE-R or XFI lobes.

My cam recommendation? 224/226 .568/.570 111LSA +4

 

Thank you very much for your response Patrick, very informative and helpful. I like the way that sounds. My only concern/question with your recomendation of a SCR of 11:1 (min) and that cam is what my DCR will end up being. I am new to the LS1 and I don't have a very good idea of what it can handle on 91-93 octane? I know that once you start going over 8.5:1 DCR that you need to start thinking about it.

If my calcs are correct then with that cam and a SCR of 11:1 then my DCR would be 8.7:1. This would be a little difficult the achive exactly and with the heads I was looking at I have two choices (aside from getting them machined again after I buy them?) 59cc and 64cc. Some of my options with these heads and gaskets would work out to be:

59cc heads with GM MLS gasket (.06 compressed)
SCR = 11.22:1
DCR = 8.87:1

64cc heads with Cometic gasket (.04 compressed)
SCR = 11.06:1
DCR = 8.75:1

64cc heads with stock GM composite gasket (.054 compressed)
SCR = 10.69:1
DCR = 8.46:1

The closest to what you say would be good is the second choice but requires the thin Cometic gasket. Would using this gasket in my situation cause me any problems down the road? And, is a DCR of 8.75:1 on 91-93 octane and issue for these engines? I already use 93 everytime I fill up anyway.

I have a feeling to be safe, I should go with the third option. 8.75:1 (if correctly calculated) just seems to be pushing it a little to far to me.

Thanks
aero

 

Pat? anyone?

 

Personally, I like the thinner head gasket and 64cc chamber to get above 11.0:1 SCR. The tighter quench will give you more octane tolerance than the same SCR with less quench.