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Compression low! Is cam in wrong?
#82778
07/01/08 05:03 PM
07/01/08 05:03 PM
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Joined: Jan 2003
Posts: 314 Kentucky
vern73
OP
enthusiast
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OP
enthusiast
Joined: Jan 2003
Posts: 314
Kentucky
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I've put together a 340 with KB hypereutectic pistons, top ring at .027 gap, should be a 10 to 1 motor and the thing is sick. Cranking compression is 120 after several turns of the engine and vacuum is about 4 in. in gear, maybe 10in. at 1000 rpm idle. It has only a few miles of street driving so I wonder if the rings have seated yet. Or maybe I somehow put the cam in wrong, even tho I degreed it I could have had a brain misfire! All I know is it is not very powerful. The combo is almost all edelbrock, new 340 heads, intake, carb, and the cam is the one they list as 308 duration and .508 lift I think, but the duration at .050 is less,, like less than 240 so the cam is not that wild. I put this engine together for a neighbor but refuse to give it back until it runs like it should. edelbrock says 417 hp with this combo but I think 250 is more like it. Any help is appreciated.
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Re: Compression low! Is cam in wrong?
[Re: vern73]
#82781
07/02/08 12:31 AM
07/02/08 12:31 AM
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Joined: Jan 2003
Posts: 1,996 s. e. pa.
calrobb2000
top fuel
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top fuel
Joined: Jan 2003
Posts: 1,996
s. e. pa.
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hi i think you are right 120 lbs is low ! i would expect 145 or more with 10-1 comp . i say move it up 4* and re test the comp . idle, power , vacuum will improve . what is your idle speed and inital timming set at ?
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Re: Compression low! Is cam in wrong?
[Re: calrobb2000]
#82782
07/02/08 01:20 AM
07/02/08 01:20 AM
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Joined: Nov 2004
Posts: 2,495 Oregon City, OR
Baxter61
top fuel
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top fuel
Joined: Nov 2004
Posts: 2,495
Oregon City, OR
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Where did you degree the cam too? Whats your initial timing at? No, your rings havent seated yet, but I doubt your cranking comp is going to come up to more than 140 or 150 after it does, but thats plenty for it to run good. It sounds like you have the eddy Perf. RPM cam in there, that thing is probably going to like 16 initial, I know mine did. But even at 12 initial you should be pulling more than 4 inches of vaccuum, that cam isnt that big.
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