Compression too high?
Thread Starter
Racer
Joined: Dec 2003
Posts: 399
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From: Haslet,Texas
Compression too high?
Well, I finally got my Vortec heads torqued on. Because of all the problems I've been having with my old heads, I did a compression test before putting the rest of the upper end together. This was to ensure the problem was with my old heads and not my block. The good news is that the compression test showed all the cylinders to be pretty close on their readings. The bad news is that they all ranged between 170 and 180. Is this too high? For some reason I was expecting between 140-160.
Thread Starter
Racer
Joined: Dec 2003
Posts: 399
Likes: 0
From: Haslet,Texas
Yes, the starter is what I used to turn the engine. I have flat-top pistons, so I'm sure the compression is up there. I just hope it isn't too high up there. I don't mind using premium fuel, but I don't want to have to go beyond that.
Race Director
Joined: Apr 2000
Posts: 17,665
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
My L48 with Sportsman II iron heads was 230psi across the board, it would run on pump gas with timing set at 40 degs. no vacuum advance, no problem 
Racer
Joined: Jul 2005
Posts: 317
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From: PA
Your cam profile will make all the difference in the world on these pressure readings, what your looking for is consistancy, your higher rpm cams generally will have lower cylinder pressure because of centerline, overlap and duration.
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Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by 73'Vette
compression test showed all the cylinders to be pretty close on their readings. The bad news is that they all ranged between 170 and 180. Is this too high? For some reason I was expecting between 140-160.
http://www.campbellenterprises.com/R...o%20calculator
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by 80TexasC3
L48 with Edelbrock RPM 64cc & SRP flattops here...
11.5:1 run 93 octane no problems...
11.5:1 run 93 octane no problems...
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
Originally Posted by 73'Vette
Thanks for the help guys. I guess this weekend I'll be finishing reassembly and hopefully go for my first cruise I've had in months.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
jackson -
I agree - If he has an otherwise stock engine and slaps the 62 or 64cc heads on it with a stock-type gasket set, he'll probably be around 9.5:1 - should run great on regular pump gas on the street.
I agree - If he has an otherwise stock engine and slaps the 62 or 64cc heads on it with a stock-type gasket set, he'll probably be around 9.5:1 - should run great on regular pump gas on the street.
Race Director
Joined: Sep 2005
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From: Farragut,TN
lars, what do you charge to put your golden hammer on a q-jt rebuild and a distriburetor? the car is a '69 350/300 four speed have offidle surging and high speed problems. you can contact me off line at amanns@tds.net
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
Team Owner
Joined: Jan 2004
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From: NJ
Originally Posted by MotorHead
My CR was about 10:1 and I got ~ 230psi with both CC270H and CC282S cams
My last build was a Pontiac 455 with .30 milled 6x heads and had 230 with a 10.5 calculated CR. The car ran super with no problems.