Compression Ratio help..

[blk00z28]

So I've been thinking it over. I know my head are small (60cc). But I was wondering what exactly will my CR be? I'll be using the Stock crank, eagle rods, .030 over bore, JE pistons (I don't know the numbers on the pistons off hand, they are our replacements..). I don't know the deck height or gasket thickness to factor in.

I'd like to know that way if it is going to be to high I can send the heads off and have them open the chamber up a little. I probably should have figured this out a while back but it slipped my mind until I was looking at everything the other day.

I think I read once that the larger bore will increase the CR. So if anyone that knows how to figure this out would be so kind as to do my build with the stock bore, and then a .030 to see what the difference would be. Because my cylinder walls still look great and if I can get away with only a hone and using some stock size stuff that'd be great.

 

[dgoodhue]

Re: Compression Ratio help..

So I've been thinking it over. I know my head are small (60cc). But I was wondering what exactly will my CR be? I'll be using the Stock crank, eagle rods, .030 over bore, JE pistons (I don't know the numbers on the pistons off hand, they are our replacements..). I don't know the deck height or gasket thickness to factor in.

I'd like to know that way if it is going to be to high I can send the heads off and have them open the chamber up a little. I probably should have figured this out a while back but it slipped my mind until I was looking at everything the other day.

I think I read once that the larger bore will increase the CR. So if anyone that knows how to figure this out would be so kind as to do my build with the stock bore, and then a .030 to see what the difference would be. Because my cylinder walls still look great and if I can get away with only a hone and using some stock size stuff that'd be great.

Bigger bore 4.03 increase CR by about .1. The JE Dish Piston most use are -14cc. SRP are maybe -18cc (off the top of my head) Cometic Gasket are 4.155 0.040 thick (stock gaskets are 4.125 0.040). With a 0.030, Cometic, 64cc Vortec heads (From what I have read, I think they might actually be 62 or 63cc but I never measured them.), minimal amount deck material removed, this workouts to be about 8.8:1 CR. With a 60cc heads, I would guess around 9.2:1 playing around with the formula.

 

[blk00z28]

Re: Compression Ratio help..

Ok, so I might not be that bad then.

Thanks for all the info Dave! This has been worring me for a little while now.