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Discussion Starter · #1 ·
Can someone figure out what my compression ratio will be if you have the figures? 53cc head chambers, 20cc piston dish, 4.050 bore, 3.625 stroke, 6.5 rod, 9.5 deck height, .020 head gasket. Thanks Tim
 

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Your deck height confuses me. 9.5?

How far above or below the surface of the block is the piston at tdc? should be in thousandths....
 

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Originally posted by TIM BARNUM:
Can someone figure out what my compression ratio will be if you have the figures? 53cc head chambers, 20cc piston dish, 4.050 bore, 3.625 stroke, 6.5 rod, 9.5 deck height, .020 head gasket. Thanks Tim
Deck height is correct; 9.500" is .035" off of stock Stage II deck height of 9.535.

CR= total volume/total-swept volume

Swept volume = 3.625x(4.050/2)^2x3.14=49.70ci. =765.24 ccs

Total volume = swept volume+chamber cc+gasket cc+deck cc+piston dome/dish cc

deck cc=3.625/2+6.5+pin height=? Pin height for zero deck would be 1.1875; you didn't specify. I'll ASSume you go .020 shorter than that to gain minimum piston to deck clearance of .040" for proper quench.

Given that, deck cc+ gasket cc=8.44 cc
So: total volume=765.24+53+8.44+20=846.68cc.

Then: CR =total/total-swept=10.40:1

You need more dish or more gasket. Good luck.


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Orange Park, FL
various cars, some running
 

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Discussion Starter · #4 ·
The deck height is .0375 . From the pin to the top of the piston is 1.185 plus the 6.5 rod and the 1.8125 crank/2. For a total of 9.4975 - 9.535= -.0375 . If i use a .035 thick head gasket that would make 9.5 to 1 compression, if i calculated right. Please check my calculations. This is my first time. Is that size head gasket avaliable without using a copper one? Please just let me know. Thanks Tim
 

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Originally posted by TIM BARNUM:
Can someone figure out what my compression ratio will be if you have the figures? 53cc head chambers, 20cc piston dish, 4.050 bore, 3.625 stroke, 6.5 rod, 9.5 deck height, .020 head gasket. Thanks Tim

Revision posted by TIM BARNUM:
The deck height is .0375 . From the pin to the top of the piston is 1.185 plus the 6.5 rod and the 1.8125 crank/2. For a total of 9.4975 - 9.535= -.0375 . If i use a .035 thick head gasket that would make 9.5 to 1 compression, if i calculated right. Please check my calculations. This is my first time. Is that size head gasket avaliable without using a copper one? Please just let me know. Thanks Tim
If your revised data's correct (are you sure your block's not been decked, for instance?)
then deck cc is now 7.92ccs. With a .035" head gasket, gasket cc would be 7.39ccs.

Swept volume = 3.625x(4.050/2)^2x3.14=49.70ci. =765.24 ccs

Total volume = swept volume+chamber cc+gasket cc+deck cc+piston dome/dish cc

So: total volume=765.24+53+7.92+7.39+20=853.55ccs.

Then: CR =total/total-swept=9.66:1.

A composite gasket like the Felpro 1000 or 1007 will be more like .040" compressed, so the CR might be a tenth or so lower.

Unless your block's never been decked, though, it will probably have slightly less deck height than the factory spec 9.535"; if so, CR will be bumped up accordingly.

HTH..



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Orange Park, FL
various cars, some running
 

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Discussion Starter · #6 ·
Hey Kendall, Thanks for the info. The motor with all of the goodies (except cam) went to the mechanic today. Maybe I'll see it together by next month. If I'm lucky. I'll probably go with a 224/224 cam, sence I'm going to stick with the stock computer for now. And 75lb injectors and a 72 turbo. What do you think about that? Maybe high nines. Thanks Tim
 
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