closed chamber vs open chamber edelbrock heads

[joes68340s]

Hi, I know I started with the question of installing the open chambered edelbrock heads on my 340 with .020 positive deck. But is it possible or practicle to put the closed chamber heads on. I have forged TRW .030 pistons and steel rods. Some people talk about piston to head clearance and quench as the same thing. I have seen where a 440 with 12.1 popup pistons converted from open chamber iron heads to closed chamber edelbrocks. What do you think. Thanks Joe

 

[rumblefish360]

Ok, so I'm straight on this.
You want to modify your stock 340 pop-up pistons to fit the small chambered Edelbrock heads?
While there would be a slight performance gain due to a lighter rotating assembly, as in spin up the RPM quicker, the cost dosen't really justify the end. It would be better to re-do the bottom end with bigger weight savings in mind not to mention a stronger piston.

Some people talk about piston to head clearance and quench as the same thing.

This is true to a point. The quenched area is of the piston closest to the head and is only a small portion of the piston. (on a flat top piston that is.) The rest of the area is more open.
On a domed piston, the manufacture makes the dome to (Semi) fit the stock head. Work is still needed due to things like milled deck/ heads/ polishing the chambers , re-worked rods, etc..
If I was in your socks, I'd go with the correct head (Open chambered) on your pop up pistoned engine. If you change pistons in the future, you can allways mill the heads.

 

[dgc333]

A quench design has a portion of the piston come very close to a portion of the head opposite the piston. This forces all the mixture from the side of the chamber over towards the piston a a high velocity promoting better mixing and makes the engine less susceptable to detonation. This will allow you to run a higher compression ratio.

For example: My 360 with closed chamber magnum heads was built with the pistons at zero deck. With an 0.039 head gasket the flat portion of the that extends over the piston comes with in 0.039". I have 10.6:1 compression in my engine and it will run without detonation on 89 octane gas.

 

[moper]

possible? Sure. Pratical? Sure. need a thicker head gasket, and a little measuring to get the right thickness. The piostons you have are flat tops, the ones with 2 valve reliefs, right? You'll need to make sure the piston that comes out the furthest has enoughr oom to do it's thing inside the heads' chamber. Just be careful, take your time, and it's fine.