verifying static compression ratio

D

Dustytrix

Active Member
Grumpy, I am trying to verify my static compression ratio but dont think I got it right. the answer I come up with was 9.751 but I can,t figure where to put my cc volume that I got with piston tdc. I will give the measurements I have,cylinder heads volume 64, gasket thickness .039,cylinder bore 4.030,stroke 3.75,for gasket bore 4.187,piston head volume 12, and deck clearance .023. The question I have is that when I measured the cylinder volume, with piston tdc I got 20cc of fluid for that measurement but dont know where to put it in the calculation. I put 12 for the piston head volume because the pistons were 12 cc dished pistons , should I make it 32 for piston head volume? I have got lost on all this math :?: Thanks Dusty
 
"Grumpy, I am trying to verify my static compression ratio but dont think I got it right. the answer I come up with was 9.751 but I can,t figure where to put my cc volume that I got with piston tdc. I will give the measurements I have,cylinder heads volume 64, gasket thickness .039,cylinder bore 4.030,stroke 3.75,for gasket bore 4.187,piston head volume 12, and deck clearance .023. The question I have is that when I measured the cylinder volume, with piston tdc I got 20cc of fluid for that measurement but dont know where to put it in the calculation. I put 12 for the piston head volume because the pistons were 12 cc dished pistons , should I make it 32 for piston head volume? I have got lost on all this math :?: Thanks Dusty


if the piston volume measures 20cc you use 20cc regardless
your likely forgetting the deck height distance above the piston x the bore where your gaining the extra 8cc

heads volume 64,
gasket thickness .039
bore 4.030
,stroke 3.75,
gasket bore 4.187
make it 20cc for piston head volume, at zero deck.



http://www.csgnetwork.com/compcalc.html

http://www.kb-silvolite.com/calc.php?action=comp

both calculators give approx 9:5 as a result with those figures, when entered correctly,
remember your trying to keep the quench distance in about the .037-.044 range in an ideal world
 
Thanks lol and to think I had 4.0 in algebra and geometry 30 yrs ago. But when I used they calculators it reads 9.034?
 
I was hoping to get 9.5 compression could I change thickness of head gasket to get to 9.5? your calculation says 10.1 and I am coming up with 9.034 using the same calculator. Any help is well thought of.
 
I get 9.45 on the Solvite calculator. If you enter the piston volume as cc'd ,then don't you have to enter the deck height as 0?
 
Thanks for helping me again,I put in .015 head gasket and got the 9.5 cr I was shooting for. I hope that will be good enough for a 383 engine carbed type.
 
Using a .015 head gasket I get 9.97:1, but I would like Grumpy to comment on the "0" deck height thing when using the cc'd value.
 
IBob said:
I get 9.45 on the Solvite calculator. If you enter the piston volume as cc'd ,then don't you have to enter the deck height as 0?
Click to expand...


your correct
I over-looked that, while inputting the info,
thats totally correct!

thanks for catching that, I don,t know where my minds at today

because the piston volumes 12cc, but measures 20cc because its slightly down the bore, you either need to enter 20cc and zero deck or 12 cc and the piston distance below deck
 
Ok thats what I got too, 9.450 guess I can start putting heads on next week. Thanks for all the input Grumpy & Bob.
 
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