Aluminum heads and 63 vs 65cc chambers

[Dohc Rocks]

Are the 65cc combustion chambers on Speedmaster and Promaxx heads closed or open like on the Edelbrock 340 head?
If they're both closed, is there any difference in the chamber design or is it more of a case of clever marketing of casting variations?

 

[pittsburghracer]

Are the 65cc combustion chambers on Speedmaster and Promaxx heads closed or open like on the Edelbrock 340 head?
If they're both closed, is there any difference in the chamber design or is it more of a case of clever marketing of casting variations?

An Edelbrock head requires a lot of chamber work to get as good as a Speedmaster head. Both require work but the chamber on the Edelbrock head crowd the valves. Especially the intake valve.

 

[rumblefish360]

Are the 65cc combustion chambers on Speedmaster and Promaxx heads closed or open like on the Edelbrock 340 head?
If they're both closed, is there any difference in the chamber design or is it more of a case of clever marketing of casting variations?

ProMaxx purchases bare Speedmaster heads and works on them here in the U.S. in Alabama.

Addressed @

103 Rainbow Industrial Blvd
Rainbow City, AL, 35906

Below is the first few lines in there about us page;

We are a family owned business that began in 2012 by purchasing the remnants of Patriot Performance and Alabama Cylinder Head Exchange.

Click here for the page; About Us - PROMAXX Performance Products

 

[PRH]

I don’t believe any of the of the SM or PM heads are offered with the cnc machined quench pad area, making them an “open chamber”.

But, I’m sure a phone call/email to them would verify if that’s the case or not.

 

[mshred]

So the Speedmaster stuff is an open chamber head?

 

[pittsburghracer]

So the Speedmaster stuff is an open chamber head?

No

 

[pittsburghracer]

No

 

[pittsburghracer]

Edelbrock open chamber (340 style head)

 

[mshred]

I thought they were a closed chamber head from the pics, but this had me second guessing.

 

[rumblefish360]

The Edelbrock has a .060 (IIRC?) recess for the positive deck height 340 pistons. Same chamber otherwise really. The speedmasters are a copy of.

 

[pittsburghracer]

The Edelbrock has a .060 (IIRC?) recess for the positive deck height 340 pistons. Same chamber otherwise really. The speedmasters are a copy of.

The way some of you guys word things is very confusing

 

[Bodyperson]

I opted for the 65cc because I assumed the difference was some unshrouding of the valve.

 

[Demonx2]

My Eddie Rpm heads were advertised as 63cc but measured 65+ cc's. Had to mill them to get my actual CR to 10.5 in my avatar 408 (pic prior to milling).

 

[Dohc Rocks]

All I want to know is if the Promaxx and Speedmaster 65 cc chambers are just a slightly larger closed chambers or an open chamber like the Edelbrock 65 cc chambers are.

The pictures on the respective websites don't clarify this. Promaxx shows an LS combustion chamber which just adds to the confusion. I messaged both vendors and haven't head back from anyone yet.

On a related note, the recessed spark plug on these heads looks like a machining process was skipped. I wonder it there's enough material in that area to spot face the plug hole to sink the plug deep enough to at least get the ground strap in the chamber?

 

[mopowers]

Why would they even offer 63 and 65 cc versions?

 

[Bodyperson]

They are closed, like PBR and PRH already said.

 

[rumblefish360]

Why would they even offer 63 and 65 cc versions?

65 offers space for the positive deck piston height of the early 340’s.

 

[mopowers]

65 offers space for the positive deck piston height of the early 340’s.

Gotcha, that makes sense. Couldn't one just use a thicker head gasket in that case? It just seems weird to me that they'd take the time ($) to make two options if there's a readily available work around. I guess it's worth it to them.

 

[rumblefish360]

Gotcha, that makes sense. Couldn't one just use a thicker head gasket in that case? It just seems weird to me that they'd take the time ($) to make two options if there's a readily available work around. I guess it's worth it to them.

Yes, but hit up a ratio calc and run some numbers and be aware of the effects and dimensions of the chamber space area.

 

[Dale Davies]

The Edelbrock has a .060 (IIRC?) recess for the positive deck height 340 pistons. Same chamber otherwise really. The speedmasters are a copy of.

By positive, do you mean below the deck? A +0.025" deck means the piston is below the deck 0.025". When the piston comes above the deck 0.005", it is -0.005" deck height. A bit confusing but that is the way it is.
How much do 340 pistons protrude above the deck in an unmolested engine?

 

[rumblefish360]

OMG- positive is above deck

 

[Newbomb Turk]

By positive, do you mean below the deck? A +0.025" deck means the piston is below the deck 0.025". When the piston comes above the deck 0.005", it is -0.005" deck height. A bit confusing but that is the way it is.
How much do 340 pistons protrude above the deck in an unmolested engine?

In an “unmolested” 340 the spec is .018 POSITIVE deck clearance.

To actually get the compression ratio you might want the piston may have to be out of the deck 45-50 thou, maybe a bit more.

 

[Dale Davies]

OMG- positive is above deck

Just read K1 article on deck height. You are correct and that makes sense. I had read a couple of other sites that had above as -.

 

[Newbomb Turk]

Just read K1 article on deck height. You are correct and that makes sense. I had read a couple of other sites that had above as -.

I believe that is due to how some formula calculate it. I believe the Wallace calculator uses - for a positive deck height. I think anyway.

 

[Dale Davies]

View attachment 1716169836

So these heads on an early 340 would require gaskets of 0.050" compressed thickness and possibly a bit skimed off the piston crown.