Compression question

[dougs67]

How do i figure out compression.. i tried the calculator go about on a few times but my math is way off.

im redoing my 454 block as im sure everyone has read..

it is .30 over so a 461.

heads are 119cc

edlebrock performer air gap intake

cam is a elgin prostock .576 lift .050 duration

i would like to know if i can get this set up and be able to run pump gas etc. street/strip. http://www.summitracing.com/parts/ESP-B11000030/

im not sure on gasket thickness etc, or deck clearance..


at this point its over my head and any help would be greatly appreciated... thanks

[CDMBill]

You are missing some data points in the calculation. The flat top pistons make this easier with their 3 CC valve reliefs. You have your bore size, stroke, combustion chamber volume and you might assume safely that the pistons will be zero deck, that is not down in the bore. So you add the compressed gasket volume, here you have to take the spec from your gasket of choice, lets say .45. So you can readily calculate static compression with any of the available online calculators.

You haven't posted the necessary numbers for the cam specs so you can't calculate dynamic compression which is a better way to access pump gas suitability of the overall combination. I didn't give you the answer because all of the necessary data points aren't present. I did give you enough to go and get the data and then plug in the numbers. I like the calculators on the Wallace Racing site. Tell us what you find out.

[dougs67]

Thanks for the info.. ill try to dig up those other numbers tonight and keep pluggin them in..

appreciate the help

[JeffMcKC]

Its going to be around 8 to 1

The cams going to be key with this low of static comp.

[dougs67]

Found a different set up that is a little better on compression i think.. www.eaglerod.com part number 18002

says 10:1 with my application.

im guessing a dome piston isn't that great for a shot of nitrous though?? im undecided if i will spray or not. but it is all set up for it......

[Orange65]

Domes are a requirement for compression. But most of the big N2O users have what they call "softened" chambers. Not much quench area, etc. But still manage 13:1 or so. You won't do that with your engine. I see nothing wrong with a dome- I am headed that way.

[JeffMcKC]

At 10 to 1 your not stopping any flame travel with that small of a dome

[quick 52]

using nitrous on a dual plane intake is ok but it helps to put a spacer on the intake. just spray it and have fun i have a nice 150hp tune from monty at drag week 2010. its 65n 52f 5psi fp retracted tip plugs around a ngk 8 heat range 28* timing total 100+ fuel. if using pump gas 93 fuel i use a tune of 42n 36f 5psi 28* total timing stock plugs works great

[dougs67]

been doing a little more research and decided i would try and go with a 489 stroker kit. ive been crunching some numbers and as far as i can tell this set up would give me 10 to 1 i believe??


http://www.summitracing.com/parts/SCA-1-42260BE/


im kind of confused though as to why some pistons are -cc and some positives?

[JeffMcKC]

-cc means it has a dish or valve reliefs in it so its negative volume