Heads, Compression and Gaskets

[moremph]

I would like to know the ratio of compression to how much is cut off the dodge head.



For example if we cut . 010 off the head is that +1 or +1/2 of a compression # or close(if a stock gasket was used)???



A head for a truck a friend has been working on for another friend had to have 17thousanths cut off to make it flat, what would be the best gasket to run(marine i would guess . 010 bigger). We are running fire rings in this truck if it makes any difference.



Any help would be greatly appreciated!!!!



BTW this is a brand new head out of Cali'



Thanks

 

[J.R. Adkins]

Travis,



You are only going to loose 1- 2 cc's(per cyl) from decking the head. You could always sink the valves and make that up. Or not even worry about it! :-laf





J. R.

 

[nick05]

at my work taking off about . 007" is equal to 1 cc. by cutting down the head only . 017" i don't think you would even gain 1 point of compression. 1 if any but i doubt it. that's on gas engines though. maybe the same for diesels. i wouldn't sink the valve job that much because then your just going to shroud the valve and lose airflow in return hp. unless your going to do a little bit of chamber work after the valve job.

 

[TRCM]

I think if I got a NEW head, and it had to be cut to make it flat (especially . 017"), I'd send it back.

 

[WDixon27]

yea really, that not a head it's a surfboard

I think if I got a NEW head (especially . 017"), I'd send it back.

 

[MCummings]

I cut . 020 off my pistons, and . 010 off my head, and put a . 020+ HG in.



What's my '98. 5 24v compression at?



Merrick

 

[nick05]

mcummings, all depends on where the piston is in the hole. is it zero decked or is it . 030" down. what is the bore & stroke you have and cc's of your cylinder head. i could possibly help you out.



nick

 

[Hohn]

Guys, there's no rule of thumb for effect on compression. This is because it's not linear. The first . 010 will affect compression less than the next . 010, and . 030 is more than if you just took your first . 010 and multiplied it by three.



Crunch the numbers and you'll see. It's like having kids. When you go from having one kid to two, you have a 100% increase in the number of kids you have. The third kid is only 50% more than 2 kids, and 4 kids is only 33% more than 3 kids-- etc etc.



It *is* linear with respect to CCs, like JR mentioned, but NOT with respect to compression ratio.



jh