View Poll Results: Mast or PRC
Multiple Choice Poll. Voters: 16. You may not vote on this poll
Head Choice
Instructor
Joined: Aug 2003
Posts: 217
Likes: 3
From: Bardstown Ky
What was your compression with the old setup?
A 232 duration cam isn't too big for a 434, the lift is manageable with good springs like a PAC 1521. People forget a .623" lift LS1/2/3/6 cam becomes .660" lift with LS7 rockers. You really need light valves though, something under 90-95 grams would be great. If you order some of these big heads you're talking about, spend the extra money for the titanium intake valves.
Thread Starter
Burning Brakes
Joined: Feb 2004
Posts: 885
Likes: 0
From: Point Pleasant wv
Which heads did you have?
What was your compression with the old setup?
A 232 duration cam isn't too big for a 434, the lift is manageable with good springs like a PAC 1521. People forget a .623" lift LS1/2/3/6 cam becomes .660" lift with LS7 rockers. You really need light valves though, something under 90-95 grams would be great. If you order some of these big heads you're talking about, spend the extra money for the titanium intake valves.
What was your compression with the old setup?
A 232 duration cam isn't too big for a 434, the lift is manageable with good springs like a PAC 1521. People forget a .623" lift LS1/2/3/6 cam becomes .660" lift with LS7 rockers. You really need light valves though, something under 90-95 grams would be great. If you order some of these big heads you're talking about, spend the extra money for the titanium intake valves.
Thread Starter
Burning Brakes
Joined: Feb 2004
Posts: 885
Likes: 0
From: Point Pleasant wv
ISIS SUCKS FAT CHOAD
Joined: Oct 2008
Posts: 8,124
Likes: 53
From: Earth, United States
I have the first PRC 265cc heads.The compression on the old setup was 11.4 but the Dale talked me into using a .120 head gasket to lower compression. So its around 8.9 now. I going to the titanium valves also. I have the Manley NEXTEK VALVE SPRINGS for .700 lift kit. I bought the kit from Ragin Racin.
ISIS SUCKS FAT CHOAD
Joined: Oct 2008
Posts: 8,124
Likes: 53
From: Earth, United States
I have the first PRC 265cc heads.The compression on the old setup was 11.4 but the Dale talked me into using a .120 head gasket to lower compression. So its around 8.9 now. I going to the titanium valves also. I have the Manley NEXTEK VALVE SPRINGS for .700 lift kit. I bought the kit from Ragin Racin.
Instructor
Joined: Aug 2003
Posts: 217
Likes: 3
From: Bardstown Ky
I have the first PRC 265cc heads.The compression on the old setup was 11.4 but the Dale talked me into using a .120 head gasket to lower compression. So its around 8.9 now. I going to the titanium valves also. I have the Manley NEXTEK VALVE SPRINGS for .700 lift kit. I bought the kit from Ragin Racin.
A .080" increase in gasket thickness lowers the compression 1.8 points, so 11.4 would become 9.6
If you were using a more common gasket thickness of around .050" then the .070" change to get to .120" will only drop the compression down to 9.76
Here is the compression calculator that I use.
http://www.csgnetwork.com/compcalc.html
If the engine is "lazy" now, I don't think a bigger head is going to help that.
Last edited by Brian Tooley C5; Nov 5, 2011 at 12:00 PM.
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ISIS SUCKS FAT CHOAD
Joined: Oct 2008
Posts: 8,124
Likes: 53
From: Earth, United States
Agreed with Brian.
If your already at 9.6 to 1 as Brian suggest you are with those gaskets then that's where u need to keep it. Also as Brian stated if the engine was lazy before huge heads arent going to help. My question is why was the engine lazy to begin with at that compression ratio? Did u have a tiny or stock cam? Was there an issue with there being too much engine and not enough cylinder head? That engine at the compression ratio u stated shouldn't have been lazy. One of the first things I think of after reading here is that the static compression ratio wasn't where u though it was.
If your already at 9.6 to 1 as Brian suggest you are with those gaskets then that's where u need to keep it. Also as Brian stated if the engine was lazy before huge heads arent going to help. My question is why was the engine lazy to begin with at that compression ratio? Did u have a tiny or stock cam? Was there an issue with there being too much engine and not enough cylinder head? That engine at the compression ratio u stated shouldn't have been lazy. One of the first things I think of after reading here is that the static compression ratio wasn't where u though it was.
You can't lower the compression on a 427 from 11.4 down to 8.9 with a .120" head gasket, assuming you started with something as thin as a .040"
A .080" increase in gasket thickness lowers the compression 1.8 points, so 11.4 would become 9.6
If you were using a more common gasket thickness of around .050" then the .070" change to get to .120" will only drop the compression down to 9.76
Here is the compression calculator that I use.
http://www.csgnetwork.com/compcalc.html
If the engine is "lazy" now, I don't think a bigger head is going to help that.
A .080" increase in gasket thickness lowers the compression 1.8 points, so 11.4 would become 9.6
If you were using a more common gasket thickness of around .050" then the .070" change to get to .120" will only drop the compression down to 9.76
Here is the compression calculator that I use.
http://www.csgnetwork.com/compcalc.html
If the engine is "lazy" now, I don't think a bigger head is going to help that.
Instructor
Joined: Aug 2003
Posts: 217
Likes: 3
From: Bardstown Ky
http://forums.corvetteforum.com/c5-f...n-runs-8s.html
Last edited by Brian Tooley C5; Nov 6, 2011 at 11:20 AM.
