compression ratio

shmirk · Post by **shmirk** » Tue Feb 11, 2003 6:28 am

I don't want to sound dumb, How do you figure out your compression ratio? I have 94's with .053 deck height pauter heads 40 x 32 .478 lift 284 dur 1.25 rockers

Shmirk

turboblue · Post by **turboblue** » Tue Feb 11, 2003 9:54 am

Shmirk

Gotta have your head cc's before compression can be figured.

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Gary

shmirk · Post by **shmirk** » Tue Feb 11, 2003 10:32 am

I thought I put that in there 37cc.

Post by **Marc** » Tue Feb 11, 2003 10:35 am

You'd have 11.33:1 if it's a stock 69mm stroke/no valve notches.

shmirk · Post by **shmirk** » Tue Feb 11, 2003 12:19 pm

whats the formula you use? I want to know for future refrence.

Shmirk

mharney · Post by **mharney** » Tue Feb 11, 2003 1:42 pm

Its just a ratio. Take the stroke and the bore, figure the cylindrical volume, add this to the cylindrical volume of the barrel that is a result of the deck height, add the head ccs. Add all that up, and divide it by the cylindrical volume of the barrel that is a result of the deck height added to the cylinder head volume. That's it.

The cylinder volume formula is (PI*BORE*BORE*STROKE)/4.

1CC = 1 cubic centimeter, so in your calculations using millimeters, convert it to CC's by dividing by 1000.

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Post by **Marc** » Tue Feb 11, 2003 2:04 pm

There's a bunch of calculators on the Web: http://www.type2.com/rvanness/deck.htm http://www.angelfire.com/bc/jmartin/vwcalc.html http://www.johnmaherracing.co.uk/enginecalc.htm

shmirk · Post by **shmirk** » Tue Feb 11, 2003 4:25 pm

Hey thanks for the info guy's. Glad you can help.

Shmirk.

shmirk · Post by **shmirk** » Tue Feb 11, 2003 7:33 pm

One more question on this I'm running 78 stroke whats a c.r. for this motor?

Shmirk.

turboblue · Post by **turboblue** » Wed Feb 12, 2003 8:08 am

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by shmirk:
<B>One more question on this I'm running 78 stroke whats a c.r. for this motor?

Shmirk.</B><HR></BLOCKQUOTE>

Shmirk
That changes everything. I figured it at approxomately 13:1. I think we all assumed it was a 69 stroke engine.

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Gary

[This message has been edited by turboblue (edited 02-12-2003).]

shmirk · Post by **shmirk** » Wed Feb 12, 2003 4:23 pm

I made a typo on my last post. Whats an ideal c.r. for a 2165cc? should I change my c.r.

shmirk