73dodgearcher
Active Member
Good afternoon every body, this is my first post with fabo and I was wondering if there is a way I could figure out my compression ratio from my cylinder psi. My motor is a 360.
compression ratio to cylinder psi
- Thread starter 73dodgearcher
- Start date
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Probably not unless it is dead stock. Because a 12:1 engine might have 150 PSI and an 8.5 engine might have 170 PSI. Cylinder pressure and compression ratio are related, but not "connected" you might say.
Baxter61
Well-Known Member
if you knew when the intake valve closed couldnt you reverse calculate your way into a close guestimate? just thinking out loud here
73dodgearcher
Active Member
thank you very much.
dartsport74
Well-Known Member
Not to hijack things here,
but how would you then go about determining how much compression you really have??
but how would you then go about determining how much compression you really have??
73dodgearcher
Active Member
Rebuilt 360
340 j heads ported w/ 2.08 intake and 1.62 exhaust valves
mp 528 cam
Kb flat tops
Eddy performer rpm intake
that is all the info got on this motor. Thanks
340 j heads ported w/ 2.08 intake and 1.62 exhaust valves
mp 528 cam
Kb flat tops
Eddy performer rpm intake
that is all the info got on this motor. Thanks
Nope. How is that going to tell piston head volume, combustion chamber volume, deck clearance and a myriad of other variables? The only way for sure to be accurate with an unknown combination is to disassemble and measure. If it has strong cylinder pressure, that just means it's in good shape and a good combination. That's no indicator of static compression ratio whatsoever.
If you can provide a piston part number, we can probably get a fairly close guess. If it is the KB107, you could have from 8.8 to 11.1. Get number one plug out and get a compression reading. With the info we have now, we can give you a good guess with the compression pressure. Why didn't you give us all that to begin with? lol
73dodgearcher
Active Member
I am just going not worry about it. Thanks for the replies
73dodgearcher
Active Member
157 Lbs
73dodgearcher
Active Member
Please excuse me I am very new to this.
My guess is that with "only" 157 PSI, no extra machine work was done such as block decking or head milling. IMO, it probably has 8.8-9.1 static compression. I also think that if that cylinder pressure is correct, a smaller camshaft would provide a power increase by increasing cylinder pressure. That said, it's probably a pretty nice little combo for a street motor. How does it run?
73dodgearcher
Active Member
It sounds great. I hope to have it out on the track in 3 to 4 weeks. I will keep you posted. Thank you strokerscamp. For your input
No problem. I wouldn't really worry too much about numbers. If you're happy with how it runs, that's all that counts. That's a great cam you have in it.
1wild&crazyguy
Banned
if take the int closing engine specs and play with static assumptions....you can figure it out.
http://www.wallaceracing.com/dynamic-cr.php
http://www.wallaceracing.com/dynamic-cr.php
1wild&crazyguy
Banned
9.2-1 comp....cause if i remember right....that cam int closes at 52*
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