ZR1 Increase Compression ratio
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,376
Likes: 4
From: Hershey, PA, USA
Cruise-In VI Veteran
St. Jude Donor '12
ZR1 Increase Compression ratio
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?
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?
Melting Slicks
Joined: Apr 2007
Posts: 2,987
Likes: 16
From: Phoenix
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.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,376
Likes: 4
From: Hershey, PA, USA
Cruise-In VI Veteran
St. Jude Donor '12
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.
Le Mans Master
Joined: Jul 2010
Posts: 5,407
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From: montreal quebec
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!
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Le Mans Master
Joined: Dec 2005
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From: Southeast TX
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.
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.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,376
Likes: 4
From: Hershey, PA, USA
Cruise-In VI Veteran
St. Jude Donor '12
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.
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.
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.
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.
Last edited by C5kid; Dec 16, 2013 at 08:56 AM.
Race Director
Joined: Dec 2006
Posts: 12,389
Likes: 2,910
From: Fort Worth, Texas
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.
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.
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
Last edited by PRE-Z06; Dec 17, 2013 at 07:04 PM.
Thread Starter
Melting Slicks
Joined: Feb 2001
Posts: 3,376
Likes: 4
From: Hershey, PA, USA
Cruise-In VI Veteran
St. Jude Donor '12
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
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.
Melting Slicks
Joined: Mar 2012
Posts: 2,206
Likes: 22
From: San Diego CA
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.
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.
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.
Race Director
Joined: Dec 2006
Posts: 12,389
Likes: 2,910
From: Fort Worth, Texas
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
Last edited by PRE-Z06; Feb 25, 2014 at 07:19 PM.