Cascade Crew

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

So I pulled the heads off of my car today so that I can get the valve guides replaced. I was finally able to measure how deep the piston is in the hole.

I have this

Chamber - 64cc
Head gasket .040"
Piston in hole .045"
4 valve reliefs 6cc

This gives me an 8.22 to 1 compression ratio. Sad

Since I can't do anything about the piston in hole measurement I was thinking about running a .015" head gasket which would at least help the quench and bump the compression up to 8.7. Anybody have any experience with the thin gaskets?

Also I had two exhaust valves that are so bad that they are about 1/16th" smaller in diameter than the rest, the face on them is shaped like a cup with a ridge around the edge. They were still sealing though. Laughing

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

In conjunction with a smaller head gasket, you could have some head work done (i.e. oversized valves, pocket porting), and have the heads shaved for trueness, which would bump the compression ratio a tad as well.

Remember though that your cam will effect your compression ratio, there's a difference between static and dynamic compression ratio Smile

chevymad · Posted: Sun Oct 28, 2007 8:49 pm Post subject:

Go ahead and run the shim gaskets Rod. I beleive Paul allready is running them, and i've got a set on my 454 too. Just spray them with coppercoat before you put them on. A slight mill on the heads wouldnt hurt anything, but won't fix your quench problem. If you go too high on the compression with that wide a quench, you'll be pinging. Almost sucked 2 valves eh? That kinda sucks. On the positive side.. you'll be getting a few more ponies!

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Right on!

Hopefully I'll have time this week to look for a machine shop that I like. Get these things back on.

Schultzy89GTA · Posted: Sun Oct 28, 2007 8:54 pm Post subject:

Leave the CR where it is at and boost it Thumbs up

-Schultzy

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Twilightoptics · Posted: Sun Oct 28, 2007 9:20 pm Post subject:

Rod.... Are you sure your pistons are 6cc? I have flat tops with 4 reliefs and it's 8.65. Also, what's the bore of your head gasket?

With the rest of your specs and a 30 over 350 I come up with:

At 6cc and 4.125 bore
9.25:1

With 8.65 CC pistons:
9.05:1

With 4.1 bore and 6cc pistons
9.26:1

With 4.1 bore and 8.65cc pistons:
9.02:1

With a .015 steel shim 4.1 Bore Felpro-1094:
9.52.

Dynamic compression with your cam:
7.7:1

You're right there to run on 87/89 octane if you stick the steel shim in.

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Twilightoptics · Posted: Mon Oct 29, 2007 9:56 am Post subject:

That with 6cc pistons puts you at : 9.158:1.

I put the bore in the calculator as 4.002 (Was told by my machine shop when you hone it for rings it takes about 2 thou off.)

That shim gasket will then put you at 9.69:1.

Make sure you check and check and check the deck height. Check different pistons too... if you haven't already.

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Ok, I see that your calculator ads the chamber volume to the displacement, then divides it by the chamber volume. How can the cylinder pull in more air NA than the actual displacement?

That same math would put your engine at 10.2 CR

BigDaddyVu · Posted: Mon Oct 29, 2007 3:58 pm Post subject:

read this link. This also has a formula table to figure it out aswell. http://www.imperialclub.com/Repair/Engine/compression.htm

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Right on!

I was wrong in how I was figuring that. Laughing

So is 9.7 too high? Should I just put it back the way it was?

chevymad · Posted: Mon Oct 29, 2007 7:55 pm Post subject:

I think 10:1 is supposed to be the limit with iron heads. I'd probably still run the steel shim just to get the quench better. Ever calculate your DCR?

rjmcgee · The Hammer Joined: 08 Jan 2004 Posts: 2328

Paul said the DCR was 7.7 to 1. I'm pretty content to agree with him at this point.

New problem though, tonight I started looking at the bores close and have a scratch/gouge in #6 that I can catch my fingernail on. Ends right at the top of the wear area like a ring is stuck and scratching the cylinder wall. Not sure what to do about it at this point.

Anybody seen any good buys on 6.0 pickup engines lately?

Twilightoptics · Posted: Mon Oct 29, 2007 9:50 pm Post subject:

Read this: http://members.uia.net/pkelley2/DynamicCR.html

And download the calculator at the bottom.

It's all about the dynamic baby.

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

Twilightoptics · Posted: Mon Oct 29, 2007 10:18 pm Post subject:

Oh yes.... we are suggesting cam.

The heads I thought were still pretty okay?

chevymad · Posted: Mon Oct 29, 2007 10:24 pm Post subject:

The escalade engine is the one you really want. Beleive they're 345 to start with and a cam/intake/chip change add another 125.

blue89 · Posted: Tue Oct 30, 2007 8:19 am Post subject:

Isn't the escalade engine an LS7 in disguse?

My friend got me thinking of a 2004 RWD Northstar engine. I really think that my next swap might be a turbo charged 350.

-t