but more important is that all cylinders are the same + or - 5lbs
Cranking Compression
Drifting
Joined: Jun 2007
Posts: 1,552
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From: Lake Villa Illinois
St. Jude Donor '14
Thread Starter
Safety Car
Joined: Dec 2009
Posts: 4,171
Likes: 335
From: Homewood Alabama
Im trying to see if a cam is not advanced enough because the power is low after a recent rebuild-cam was apparently installed straight up without being degreed. I was told by a person to check the cranking compression and if the cranking compression was low, that it would indicate if the cam was too retarded. however, i was not given a specific PSI that would be considered too low or too high. I read online in an article that 160psi was low and that 220 was high. I guess it really just depends on the particular engine and its components and that is why i asked here. This engine was a stock 427/390 rebuild with the stock compression ratio.
Thanks
Thanks
Le Mans Master
Joined: Sep 2008
Posts: 5,662
Likes: 2,344
From: Lake Minnetonka, Mn
2018 C1 of Year Finalist
Im trying to see if a cam is not advanced enough because the power is low after a recent rebuild-cam was apparently installed straight up without being degreed. I was told by a person to check the cranking compression and if the cranking compression was low, that it would indicate if the cam was too retarded. however, i was not given a specific PSI that would be considered too low or too high. I read online in an article that 160psi was low and that 220 was high. I guess it really just depends on the particular engine and its components and that is why i asked here. This engine was a stock 427/390 rebuild with the stock compression ratio.
Thanks
Thanks
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Le Mans Master
Joined: Nov 2008
Posts: 5,691
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From: columbus oh
if it's running badly, i would first check the advance mech. in the dist. and also initial timing...jmo...
Melting Slicks
Joined: Nov 2002
Posts: 2,460
Likes: 5
From: Wheaton IL
Im trying to see if a cam is not advanced enough because the power is low after a recent rebuild-cam was apparently installed straight up without being degreed. I was told by a person to check the cranking compression and if the cranking compression was low, that it would indicate if the cam was too retarded. however, i was not given a specific PSI that would be considered too low or too high. I read online in an article that 160psi was low and that 220 was high. I guess it really just depends on the particular engine and its components and that is why i asked here. This engine was a stock 427/390 rebuild with the stock compression ratio.
Thanks
Thanks
What was your MEASURED compression ratio?
Brian
Thread Starter
Safety Car
Joined: Dec 2009
Posts: 4,171
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From: Homewood Alabama
Heads were ccd in right around 101 and the pistons used were the speed pro 16.8 forged pistons from speed pro, with a .038 thick gasket from felpro. The block has never been decked, so that should put it in the range of around 10.2:1 compression. That should be perfect for the stock cam, which wasnt very big.
I havent checked the cranking compression yet. Should the throttle be held open?
I havent checked the cranking compression yet. Should the throttle be held open?
Melting Slicks
Joined: Nov 2002
Posts: 2,460
Likes: 5
From: Wheaton IL
Heads were ccd in right around 101 and the pistons used were the speed pro 16.8 forged pistons from speed pro, with a .038 thick gasket from felpro. The block has never been decked, so that should put it in the range of around 10.2:1 compression. That should be perfect for the stock cam, which wasnt very big.
I havent checked the cranking compression yet. Should the throttle be held open?
I havent checked the cranking compression yet. Should the throttle be held open?
Brian
Le Mans Master
Joined: Sep 2008
Posts: 5,662
Likes: 2,344
From: Lake Minnetonka, Mn
2018 C1 of Year Finalist
