Compression ratio calculators??
 

I've used a few different sites that come up with 3 different numbers.
Specs are 3.484 bore, 3.976 stroke, 10.2 cc dome, deck height 0, gasket thickness .074
gasket bore 3.51. Cylinder head volume 48 cc's
The sites I've found vary by as much as 2 full points (13 to 1 up to 15 to 1) Using the same input data (some of the sites don't ask gasket bore size) I would think it shoulkd be within half a point.

Re: Compression ratio calculators??
 

You have a PM
You have more than enough

Re: Compression ratio calculators??
 

Art, did you try Wallace Racing calc?

http://www.wallaceracing.com/cr_test2.php

Re: Compression ratio calculators??
 

I find this site is real simple for numerous race calculations:
http://users.erols.com/srweiss/index.html

Re: Compression ratio calculators??
 

What gets me is I get 15.70 on one site 14.62, 16.30 on another
This is with putting the same numbers in Some take in to account the head gasket bore others don't. But it shouldn't come to 2 full points. I think there is a formula in an old rule book I can do on paper.

Re: Compression ratio calculators??
 

Artie,make sure you bolt that hood down good and tight.............................................

Re: Compression ratio calculators??
 

Ed I have my front mounted parachute on that hood

Re: Compression ratio calculators??
 

Art,
I think there is a formula in both the How to Build Books. Both Small Block and Big Block. I have it on my shop computer and will PM it to you tomorrow. It will come out with in a .00 of what I sent you.
Adger

Re: Compression ratio calculators??
 

Useing your info. Above i got 13.540:1, normally aspirated at sea level........this is an older computer program i use with sprint car
motors.

Re: Compression ratio calculators??
 

I'm going to run the motor the way it is. But I was perplexed at the variation in the different programs. I wonder if the calibations are done by nhra in different divisions LOL.

Re: Compression ratio calculators??
 

13.54 to 1

I look at as the volume with the piston at bdc divided by the volume with the piston at tdc

convert all values to cc's is easiest for me

16.387 cc's per cu inch

bore and stroke volume + deck volume + chamber volume +gasket volume-dome volume
divided by
deck volume + gasket volume + chamber volume - dome volume

Re: Compression ratio calculators??
 

Thats the way i thought it was calculated. But why are the calculators on line so far off? It seems like simple math to me. I just wasn't sure of the formula.

Re: Compression ratio calculators??
 

In doing a little number movement with most of the on line calculators I think they are not figuring the dome vol. + or - properly in the formulas.
Art,
Daves formula was the one I had at the shop that I said I would PM to you.

Re: Compression ratio calculators??
 

Mine also converts everything to cc's so i can do a "pour check" with a burette thru the spark plug hole as a double check before the motor is sealed. At least we've found some consistency in a couple of programs.... Everybody have a good thanksgiving.

Re: Compression ratio calculators??
 

I have a compression ratio calculator on my website that seems to be very accurate. www.racingenginetechnologies.com/services
Please let me know what you think.

Thanks,

Chris Hardy

Re: Compression ratio calculators??
 

A couple of the ones that I tried consider piston dome as a positve number, some consider it a negative number.

Re: Compression ratio calculators??
 

Yes but even when entered correctly they vary by a lot. The one thing I have figured out is my new motor has about 1 more in the compression ratio.