[rohrt]

I know their are other Pontiackers that are running 11:1 with aluminum heads and running just fine. I guess its better to be safe then sorry.

[Bruce K]

10.77 here, and no problem with pump premium. Also, the engine keeps begging for more advance, seems to like 38+.

The amount of compression the engine can take depends alot on what cam you choose and how it is timed.

[Steve C.]

Ok between the two, and setting aside the minimal differance in air flow.

One set-up with a little deeper chamber and flat top piston, with no dish and only valve reliefs, for 10.5 compression. And the second with a little shallower chamber and a piston with a 20cc dish for the same 10.5 compression.

Is there any flame front and/or burn pattern issues with the deeper 20cc dished piston compared to the flat top piston ?

I was told by a friend about a discussion years ago with Jim Butler and at the time Jim favored a flat top. This came during a discussion about milling out a dish on a TRW piston to make them pump gas friendly with a small chamber iron head.

[b-man]

Originally Posted by Steve C.

Ok between the two, and setting aside the minimal differance in air flow.

One set-up with a little deeper chamber and flat top piston, with no dish and only valve reliefs, for 10.5 compression. And the second with a little shallower chamber and a piston with a 20cc dish for the same 10.5 compression.

Is there any flame front and/or burn pattern issues with the deeper 20cc dished piston compared to the flat top piston ?

I was told by a friend about a discussion years ago with Jim Butler and at the time Jim favored a flat top. This came during a discussion about milling out a dish on a TRW piston to make them pump gas friendly with a small chamber iron head.

From what I've read, putting as much of the combustion chamber as you can in the piston itself is beneficial.

Aren't some of the best engine builders using heads with a tiny or even close to no combustion chamber along with a properly shaped dish in the piston these days?

I know this is the street forum, but wouldn't it be a good idea to mimic this type of build on a street engine if the additional cost for a properly dished piston is somewhat minimal in comparison to the rest of the build? That's all I'm getting at.

[Steve C.]

I don't disagree. I know little on the subject and putting forth conversation to get opinions. My 505 build is using a custom 27cc reverse dome piston with 72cc Edelbrock castings for about 10.2-10.3 compression. They are a JE piston very similar to the one Andy Mitchel used in his 505 Road Warrior build in the Dec 2005 Hot Rod on pg 128.

[Skip Fix]

Gosh no one has even brought up the old too big race head argument!

I want to think my Ross dish were around $550.

[Skip Fix]

My conversation with Dave Bisshop was for the little HP increase for 10.5-11.0 for E heads why take a chance if you get stuck having to get some low grade pump gas while really street driving it on an expensive motor? We went with 20cc dish with mine on a 455 to stay 10.25. I had the 72s in case we were to put them on a 400 they would interchange and not be too low.

On the dyno increasing octane over 93 did nothing for the motor.

[Hooter]

Originally Posted by Skip Fix

My conversation with Dave Bisshop was for the little HP increase for 10.5-11.0 for E heads why take a chance if you get stuck having to get some low grade pump gas while really street driving it on an expensive motor? We went with 20cc dish with mine on a 455 to stay 10.25. I had the 72s in case we were to put them on a 400 they would interchange and not be too low.

On the dyno increasing octane over 93 did nothing for the motor.

Ditto - Dave told me the same 3 years ago when building my combo.