what would compression be

#1
so im doing a budget rebuild on my 140 block

im going to be using these pistons Wiseco PTS542A2=3.820 Compression Height= 1.825 Dome Volume=-25cc
i will be using stock 2 dot rods and stock 8445 heads
i don't know which head gaskets yet. any input?

just trying to figure what the compression will be im hoping for a little over 8.1:1
 

dank GN

BlackArts Automotive (661)993-8277
#2
There is all sorts of compression calculators out there just google it . Then play with your head gasket thickness to get the compression where you want it
 
#8
There is all sorts of compression calculators out there just google it . Then play with your head gasket thickness to get the compression where you want it
I did most of that but I don't know the deck clearance . So when I enter everything that is the only thing I don't know so It won't give me a reading unless I throw a number in there's
 

earlbrown

runs with scissors
#12
so im doing a budget rebuild on my 140 block

im going to be using these pistons Wiseco PTS542A2=3.820 Compression Height= 1.825 Dome Volume=-25cc
i will be using stock 2 dot rods and stock 8445 heads
i don't know which head gaskets yet. any input?

just trying to figure what the compression will be im hoping for a little over 8.1:1
You have to know how tall you block is, your exact rod length, and the exact CCs of your heads before you can do the math.

I don't know your numbers, but I'm guessing you're going to have very low compression and out of any kind of quench range by the time you add as gasket.

I happened to have a sheet sitting here on a set of 20 overs I made a few months ago and the inverted dome is 3cc's smaller than the Wisecos and the CH is .037" taller. Those two numbers by themselves are worth 14.429CCs.
 

earlbrown

runs with scissors
#13
14+CCs is a wad in the grand scheme of things. To get those back would require (most likely) decking the crap out of the block, shaving the heads as much as you can get away with (so much, the pushrods will have to be changed), going OS on the intake vale to sink it into the combustion chamber and installing 6 exhaust seats so those valves can be sunk too. Then machining the intake so it'll fit again since the heads are so much lower.

On the upside, if the machinest is compentent, and cares, with four freshly machined (not belt sanded) surfaces, a set of $200 .027" Cometics might get you there.


This one's not as accurate as a real calc, but it's easy to use and pretty close to the real number. I'll read a little higher than actual.
https://www.summitracing.com/newsandevents/calcsandtools/compression-calculator