Compression Ratio, Too High...Too Low ??? |
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Compression Ratio, Too High...Too Low ??? |
2-OH! |
Sep 6 2007, 05:44 PM
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#1
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Senior Member Group: Members Posts: 552 Joined: 17-October 03 From: Santa Clarita, Kalifornication Member No.: 1,253 |
Ok folks,
We just finished rebuilding the motor...94mm pistons and cylinders to match...71mm stroke...but old 1.7 case...CC'd the heads and come up with 44 cc's per cylinder... Do the calculations and we come out with 1971 cc's...Great !!! But, The problem is the compression ratio is now 10.64 to 1... The question of the day: Should I take the cylinders and heads back off and shim them to get a little relief...Probably not going to get much...Might knock it down to 10 or 9.75 (if I'm lucky)... DO NOT want this thing to clatter and diesel on me when I get it back together... OK, let me have it...What are your thoughts ??? 2-OH! |
Brett W |
Sep 7 2007, 12:24 AM
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#2
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Advanced Member Group: Members Posts: 2,856 Joined: 17-September 03 From: huntsville, al Member No.: 1,169 Region Association: None |
Toss the Djet, buy a nice cam Web 163/86b, or similar variant. Put some carbs on there with a nice exhaust and you will have a very good street engine. Yes you will have to run premium, but watch your timing and you will be fine.
Do not throw a shim under the heads. Decreasing the compression by increasing the deck height is an awful way to accomplish the goal. Your 9.5 engine will ping worse than your 10.5 engine will. Just put more cam in and lower the dynamic compression ratio. Or open the chambers up and decrease the compressed volume. If you would go with a programmable fuel injection system you could probably go a little higher and still run it on pump gas. |
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