Low compression

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Low compression


Post by Elvis » Thu Jan 22, 2004 2:55 pm

Been trying to figure out the same thing a lot of you are. Have a 56 Pan with an Aristocrat (Sifton 412) cam in it. I can practically turn the thing over by hand though. People have told me that taking static compression readings on a Pan are worthless by standard reading because of the valve overlap. It's this reason that I do not have any readings to offer because I havn't taken any.
I know the valves, springs, rockers, lifters, tappets, and the like are all in good order as I rebuilt everything recently.
When cold it's a three kicker, and when hot it's a solid one. I'm not worried about it, I just remember when I bought it, I had to practacally stand on the kicker to get it over, and when she was bitchy, I better had a hold of the bars cause she'd put you over. At that time the engine had some considerable mileage on it too.
The cam was spaced wrong though, and the shim, thrust washer badly scored the cam. Since then I've gone though an A, a J, and now I have this 412 Sifton.
I put 8.5/1 pistons in it, an E carb with a velocity stack, drag pipes, auto advance breaker, just for your information. I'm about ready to rip the cylinders out of it and mike them, but I've only got about 1000 miles on it in the last 5 years(that's when them engine was built).
Does anyone have any valid numbers for static compression?? In another post (Timing for another beer), 80 psi was considered high by one of the comments.

Any help would really rock, cause as usual H-D won't pull their head out of their a-- for under a billion dollars and an Evo motor.


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Joined: Fri Jul 13, 2007 8:47 am

Re: Low compression


Post by 57Kicker » Thu Jan 22, 2004 7:14 pm

Not sure if its any help but since youv'e had no responses yat i will offer my 2cents.
My 57 was recently checked for compression and had 90 in one jug and i think 92 or 95 in the other. can't remember front or back being higher or lower.
If it was only numbers to figure as comparison, there you have it. As for whats been done to the motor...unknown. I just got this baby in May and still trying to figure it out. Oh and not to cause you any concern or anything, but I am havibg some probs at present. Possible manifold leak...

...now i gotta go build something to test it ;) CHEERS!

Posts: 87
Joined: Sat Dec 01, 2001 1:00 am

Re: Low compression


Post by panomania » Fri Jan 23, 2004 2:07 am

I am now going through the same thing. Mine is showing 90 lbs front and back and it runs like crap when the motor gets hot. I just pulled the jugs back off and the rear cylinder has about a 1/4" of carbon! I only have 3000 miles on this motor. Its looks as though my jugs have worn just enough to keep my rings from working properly. Im hoping that new jugs and rings will remedy the problem. I am running a A- grind cam. I tried the j grind but didnt like it. Let me know what you find...

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Joined: Wed May 25, 2005 2:33 pm
Location: Stockholm-Sweden

Re: Low compression


Post by Ente » Fri Jan 23, 2004 9:48 am

recently I encounter sort of...similar problem. Run solids and had adjust the pushrods a little too tight. She was ok to start when it was cold but as soon she become warm or hot, the aluminium-rods expands more than the iron-cylinders and never close the valves (I guess) and she feels very slow. (I was used to adjust them more closely when I have an evo with solids). Maybe you have already checked this up... but just an idea.

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