Need to lower compression

[Khyron]

I just got my heads back and found out they where once shaved 60 off, then the machine shop just took another 10 off them.  The motor has been decked and only 10 removed from that.

I have 906 heads on it and am running Ross racing flat top pistons and scat rods.... What is the compression going to be at? I want this to run on Pump gas but it doesn't look promising 

[firefighter3931]

Relax  Try not to panic just yet 

Get a piston to deck and chamber volume measurement and report back. There are lots of head gasket options to adjust the static compression ratio....it can be done. 



Ron

[Khyron]

Relax  Try not to panic just yet 

Get a piston to deck and chamber volume measurement and report back. There are lots of head gasket options to adjust the static compression ratio....it can be done. 



Ron

Will do. Thanks. My Engine guys have been talking about just converting it to E85 because of the high compression and the unrealiable gas now a days, but I'm not sure I'm ready to do that yet. though it intrigues the hell out of me.

[Khyron]

o.k... sorry it took so long, but I finally got the pistons in.

The heads measured about 80cc's and the piston is to deck hight... maybe about .010 in the hole if i'm lucky.... ideas?

[Musicman]

Cylinder Bore    Stroke 

[Khyron]

Cylinder Bore    Stroke 

.030 over, standard stroke. ... it's a 440/

[Musicman]

Your compression should come in at roughly 10.9 depending on actual deck height and gasket thickness. That's a little on the high side for iron heads in my opinion... you should be shooting for something closer to 9.5

[Khyron]

Your compression should come in at roughly 10.9 depending on actual deck height and gasket thickness. That's a little on the high side for iron heads in my opinion... you should be shooting for something closer to 9.5

hmm, not as bad as I thought at least, I'll shoot for some thicker gaskets. Should still be able to run pump gas at least. That makes be feel a bit better. Thanks 

I Want to get a stud kit for the heads but all I see is a stud kit for eddie heads, anyone make any for iron heads?

[Rob R]

For every .020 of head gasket you'll loose about .5 of a point of compresion...with a Cometic .080 gasket you'll be 9.9..
I'd just grind a cam for it and bleed the cyl pressure off that way or cut 7 cc valve reliefs in the pistons or buy some alum cyl heads from 440'sRus for 900 a pair and be done with it.

[Musicman]

You may want to look at something like the SCE Copper head gaskets. Some of those can be had with a .093 compression thickness. That would bring your compression down to the 9.7 range.

[aifilaw]

There's a few people out there that run steel shims as well, that can bring it down quite a bit.

Fact is, if it were my choice, I would:
A. stick with what I got, and either bleed off quite a bit with cam overlap and be able to run low octane, or deal with what I have and urn high octane
B. Buy aluminum heads and run a no-overlap cam just fine.

[firefighter3931]

Now is the time to upgrade to a nice closed chamber aluminum head. 



Ron

[Foreman72]

http://www.popularhotrodding.com/tech/0605phr_pump_gas_secrets/index.html

hope that helps some...