CR for 400?
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Cargo Master
Joined: Dec 2004
Posts: 2,232
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From: NE Texas
CR for 400?
I am in the process of painting and freshening up the cosmetics of my 78 F150 4X4 that I bought new.
I built the 400 ten years ago, but it has seen very few miles. I milled the heads the max which I think was .040. I also did some pretty good poor boy porting on them. I used an RV cam, Edelbrock and Holley 600 along with a good, stock manifold dual exhaust system.
After the paint job, I will revisit the engine. The only thing I want to accomplish is adding compression ratio. My thinking is flat top pistons rather than heads since the heads are good save for the low compression.
What CR can I expect with flat top pistons? What about the particular custom ones that Tim provides?
I have searched alot here and have not found my specific answer.
Thanks kindly for your help,
I built the 400 ten years ago, but it has seen very few miles. I milled the heads the max which I think was .040. I also did some pretty good poor boy porting on them. I used an RV cam, Edelbrock and Holley 600 along with a good, stock manifold dual exhaust system.
After the paint job, I will revisit the engine. The only thing I want to accomplish is adding compression ratio. My thinking is flat top pistons rather than heads since the heads are good save for the low compression.
What CR can I expect with flat top pistons? What about the particular custom ones that Tim provides?
I have searched alot here and have not found my specific answer.
Thanks kindly for your help,
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
Originally Posted by MBDiagMan
I am in the process of painting and freshening up the cosmetics of my 78 F150 4X4 that I bought new.
I built the 400 ten years ago, but it has seen very few miles. I milled the heads the max which I think was .040. I also did some pretty good poor boy porting on them. I used an RV cam, Edelbrock and Holley 600 along with a good, stock manifold dual exhaust system.
After the paint job, I will revisit the engine. The only thing I want to accomplish is adding compression ratio. My thinking is flat top pistons rather than heads since the heads are good save for the low compression.
What CR can I expect with flat top pistons? What about the particular custom ones that Tim provides?
I have searched alot here and have not found my specific answer.
Thanks kindly for your help,
I built the 400 ten years ago, but it has seen very few miles. I milled the heads the max which I think was .040. I also did some pretty good poor boy porting on them. I used an RV cam, Edelbrock and Holley 600 along with a good, stock manifold dual exhaust system.
After the paint job, I will revisit the engine. The only thing I want to accomplish is adding compression ratio. My thinking is flat top pistons rather than heads since the heads are good save for the low compression.
What CR can I expect with flat top pistons? What about the particular custom ones that Tim provides?
I have searched alot here and have not found my specific answer.
Thanks kindly for your help,
Your choices as I see it now, are to run a bigger cam, or get new heads.
Tim's pistons will work well with closed chamber Aussie heads, or aftermarket aluminum heads, and will give you about 9.5:1 static CR and quench.
You could talk to Tim about increasing the dish in his pistons to bring your CR down, but you should try to get quench, if you want to run over 9.0:1 with an RV cam.
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