- Location
- Williams AZ
Rig the starter to crank very slow.
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Not a jeep...
- Thread starter SC Rednek
- Start date
- Location
- Williams AZ
Big cam will also drop you cranking compression numbers, but you'll sacrifice a little torque down low.
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
I did the math and keeping the stock deck height of 0.025, and a fairly standard gasket of 0.040, I'm getting 9.37:1 compression (feel free to double check my math, probably screwed it up). I'm finding places say PSI is usually 15 to 20 times compression, so I think I'd be in the ballpark already without changing anything.
A stainless steel shim gasket at 0.015" thick would get me up to 9.9:1, might still be under the 180 PSI limit with that
A stainless steel shim gasket at 0.015" thick would get me up to 9.9:1, might still be under the 180 PSI limit with that
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SC Rednek
NAXJA Forum User
- Location
- Winchester TN
Russ, you see any issue with the camshaft I have selected, or disagree with those numbers? If you think it's good I'm going to start ordering parts
- Location
- Williams AZ
Static compression has very little to do with cranking psi numbers. Cam will change everything. If you google dynamic compression ratio you can read all about it.
Here's a link to the calculator I've used a few times, it also compares static and dynamic using cam specs to calculate them. Unfortunately it does not appear to give approximate cranking psi.
Another minor consideration is that lower ambient air pressure will change your cranking psi numbers. So at higher altitudes it would read much lower, something to consider if you race at different elevation tracks.
http://www.projectpontiac.com/ppsite15/compression-ratio-calculator
Here's a link to the calculator I've used a few times, it also compares static and dynamic using cam specs to calculate them. Unfortunately it does not appear to give approximate cranking psi.
Another minor consideration is that lower ambient air pressure will change your cranking psi numbers. So at higher altitudes it would read much lower, something to consider if you race at different elevation tracks.
http://www.projectpontiac.com/ppsite15/compression-ratio-calculator
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
I'll give it a try tomorrow. I'll only be racing at this track, and the only rule is cranking psi.
- Location
- Williams AZ
This one does a straight calculation to psi, however you still need the cam card for the valve closing numbers in order to be accurate.
http://www.wallaceracing.com/dynamic-cr.php
http://www.wallaceracing.com/dynamic-cr.php
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
According to that, 141.6 psi at 9.4:1, 151.5 psi at 9.9:1. Both still far under the limit, looks like I'll go for the steel shim head gasket. Thanks John!
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
Parts ordered! Should be all the parts I need to finish the engine.
Front suspension is back together with new bearings, shocks, and brakes, and one bad ball joint replaced.
Front suspension is back together with new bearings, shocks, and brakes, and one bad ball joint replaced.
SC Rednek
NAXJA Forum User
- Location
- Winchester TN
Probably not the right tool. But got the job done for changing springs and seals. The hardest part of it all was drilling that stupid hole in the wrench, it dulled a few bits for some reason.
And no that is not Ford blue, it's GM blue, says so right on the spray can. I didn't want to do the normal orange because it would clash horribly with red paint.
And no that is not Ford blue, it's GM blue, says so right on the spray can. I didn't want to do the normal orange because it would clash horribly with red paint.
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