C5kid

Ok, so the winter mod bug has bitten. I'm thing of having the heads ported and while I'm there I do have the chance to mill the heads just a little and bump up the compression.

I've been doing a lot of searching and reading in this section. I do agree the ZR1 does have a hard time busting the 700rhwp range due to the low compression. (9.1:1) GM probably had the compression set to 9.1:1 to make the engine super reliable for warranty reasons.

I'm thinking of having the heads milled what ever it takes to bump up the compression to 9.75-10:1. My current mods are in my signature.

Just as a sanity check.. this would allow me to run the same or less boost and bump up the HP with out creating crazy IAT temps.

Anyone have input about this theory?

jon6.0

What fuel do you use? I'm not sure how much is safe to mill those heads either. Richard at WCCH should know. You can also use a thinner head gasket as well. Do you have a cam yet? That would be on my list as well.

C5kid

We have 93 around here. You can mill quite a bit of the LS9 heads, they have a really thick base .75"

I could use a thinner head gasket, but the LS9 9 layer gasket is pretty tough and I don't want to put a thinner one in that could be a problem.

No cam, call me crazy but I will not do a cam swap. The drivability is great with a stock ZR1 cam.

jon6.0

Mill away then! Maybe have then ported while they are off.

jon6.0

You can always add meth injection also.

turbotuner20v

do you not have access to e85?

venomws7

The heads I bought from Danny at Lethal Performance for my friend's ZR1
are milled a little (not sure how little) Also from WCCH for around 9:5 compression with stock head gaskets.

timmyZ06

Dustin that is a great idea, i too thought GM went too conservator with a very low CR. Some supra guys goes up to 10.2 CR. Your current boost setup with higher CR is the next obvious move, having said that, i would not bother with thinner HG, compromised reliability. But a head mill sound great or different pistons while you're rebuilding your motor too. Maybe some custom CP pistons, just saying!

Silver Bullet C6

You could also port the blower while it's all apart.

lt1z

Set compression at 9.5:1 and run an appropriate cam.

old motorhead

Your wanting to increase c/r is moving in the right direction. Lots of TVS2300 blown LS2's and 3's running fine with 10.7-10.9 c/r. I don't know if you can get anywhere near that without a piston swap though.

I question your reluctance to do a cam swap. You can go to a more capable cam without buying into a bunch of big cam issues. I'm ordering a 224/234 116+2 in the morning for my new Grand Sport/TVS combo. I don't anticipate any big cam issues with it. Hoping for 700 at the wheels on about 11psi.

C5kid

I'm a forum sponsor and port intakes, throttle bodies and blowers. Mine already got the treatment



Just don't want the hassle of a cam. Worrying about springs, etc.

If I can get it up closer to 10:1 with some simple mill work, then so be it. E85 is 5 miles from my house. So going to the corn juice is always an option for some more HP.

PRE-Z06

We've done a 223/235 116+2 in a CTSV with a factory stall, with headers and aftermarket catback there was only slight hint of it not being stock to a well trained ear and zero driveability issues. We've also done a small TT build with 12.5:1 which made 960rwhp on 13psi in a 402, of course it runs on E85 though. Compression is great for a bump in power across the board for better efficiency by putting more of a squeeze on the intake charge, the cam's valve events will also play a roll in the DCR which plays a roll in the octane requirement as well. Pump gas and SFI is why I believe they keep the CR low from the factory, here's a 11.25:1 centri build in case you missed it...
http://forums.corvetteforum.com/c6-f...eo-inside.html

C5kid

Great info guys. That AMS car is what got me thinking about this.

I'm not going crazy high on the compression but a bump def won't hurt it looks like.

K B Vettin

you could always spec a custom cam that has a little more lift and duration than stock. you could put it on a say a 120 or 121, stock is on a 122.5. when i had the gt9 LPE cam it had stock like drivability, no muscle car lope, smooth idle, and was on a 121.

i've been thinking of doing a piston upgrade to bump compression and pulley down to lower boost and keep same power level. this will be my last attempt to control IAT2's if that larger intercooler reservoir doesn't work.

Frans96ss

I would do it... Boost loves compression... just need to have a good tune and your fine.

PRE-Z06

just finished up a little TT 370ci 12.2:1 on E85 that made 1038rwhp SAE on our dyno at ~19psi with a single plane intake and Texas Giant cam