How accurate is this compression calculator?

http://www.rosspistons.com/CR%20Calculator.htm

For this setup, it gives a compression level of 12.42 <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" /> That seems very high.

Bore: 4.10
Stroke: 4.00
Head CC: 67
Head Gasket: 0.040 ( stock thickness )
Deck Height: 0.0001
Dish or Valve Pocket: 0.0

<small>[ September 23, 2002, 01:12 PM: Message edited by: ls1290 ]</small>

 

I get 12.4 as well.

http://www.appletreeauto.com/engcalc.htm

This is the engine calculator I used.

 

If this is true, are all the 422s out there running dish or inverted dome pistons? 12.4:1 compression would require at least 95 or 96 Octane gas if at sea level.

 

Yes it works out too 12.4:1 yes alot of the 422 runs dish pistons.
Brent
Speedahoilic
Engines & cylinder heads

 

if you have vavle relief's (which you probably do) you have a 5cc dish. that alone is 11.73. the gasket is more like .047 or so after factoring in the negitive deck (.006) and the fact that stock gaskets are actually .053 as far as I know.

also, when i put 0cc relief, .047 for gasket, and stock ls1 measurements, surprise, i get 10.17 with a 68cc head. I have heard factory clearances as low at 67 and as high as 69cc's.

<small>[ September 23, 2002, 03:23 PM: Message edited by: Ryan ]</small>

 

That is the correct compression ratio for the spec's that you have listed. Most guy's should be running a dish with the big inch LS1's, if they want to run it on pump gas. In another week we will be stocking 422 pistons for 6.125 rods and 4.000 stroke. In the following bores, 4.100, 4110, 4.120 and also 4.125. Let me know if you need anything.

Thanks,
Chris Gelineau
Diamond Pistons
877-552-2112 toll free