The Dodge Challenger Message Board

Why when we use an aluminium head with a quench dome piston don't we just machine the chamber say 0.100" like Edelbrock do with a version of their Performer heads?
It must be less work to do this than machine down the pistons. Explain please

You only need to machine the dome on the pistons if you are using closed chamber heads.

There are numerous disadvantages by machining the head instead of selecting the correct pistons to match the chamber design. The head deck is weakened, the valve to piston clearance is reduced. The intake ports may or may not be 'compromised' by a reduction in port height although angle milling is a 'trick' that was popular decades ago before raised port heads made this technique obsolete to all but the most ardent engine builders. I would rather change pistons than permanently altering my heads unless you are a class racer and are forced to use certain parts. You can make more power, reduce detonation and pre-ignition and run a higher cylinder pressure combo with small chambers and either flat top or dished pistons than can be used in a Quench Domed piston and either open/closed chambers. I think this was what you were 'talking about' Adrian?

http://www.kb-silvolite.com/kb_car/perf ... ls&P_id=29

.........cos I got these already fitted and these closed chamber Eddy heads came up cheap. I had a good look at the open chamber Eddy 's and the only difference I can see is the 0.100" relief machined into the head, taking them from 84cc to 88cc. I could check the piston/deck height and consider a thicker head gasket, but I don't really wanna tear the notor apart again, so I'll either save these for a future stroker project or sell 'em on.

Adrian Worman wrote:http://www.kb-silvolite.com/kb_car/performance.php?action=details&P_id=29

.........cos I got these already fitted and these closed chamber Eddy heads came up cheap. I had a good look at the open chamber Eddy 's and the only difference I can see is the 0.100" relief machined into the head, taking them from 84cc to 88cc. I could check the piston/deck height and consider a thicker head gasket, but I don't really wanna tear the notor apart again, so I'll either save these for a future stroker project or sell 'em on.

Yeah, I unnerstan now. It appears as you would have to machine .075 from the quench dome on the piston to fit the closed chamber heads. This would require the engine to be torn down. Using to thick a head gasket would cause severe detonation. It sucks that those pistons you have now, are chamber specific.(Open chambers)

These are what I wanted them to look like:

Eddie wrote:

Adrian Worman wrote:http://www.kb-silvolite.com/kb_car/performance.php?action=details&P_id=29

.........cos I got these already fitted and these closed chamber Eddy heads came up cheap. I had a good look at the open chamber Eddy 's and the only difference I can see is the 0.100" relief machined into the head, taking them from 84cc to 88cc. I could check the piston/deck height and consider a thicker head gasket, but I don't really wanna tear the notor apart again, so I'll either save these for a future stroker project or sell 'em on.

Yeah, I unnerstan now. It appears as you would have to machine .075 from the quench dome on the piston to fit the closed chamber heads. This would require the engine to be torn down. Using to thick a head gasket would cause severe detonation. It sucks that those pistons you have now, are chamber specific.(Open chambers)

It was a good idea at the time Eddie cos I wanted to use my iron 452 heads and get some comp and I liked the idea of the quench area technology, but now I got these I'm a bit stuck as to what to do with them.
Why's life so difficult?

Now that I understand your question, why not just machine the quench Pad on your alloy heads? This can be easily done with a Bridgeport or Valve Cutting machine that has a X Y Axis table. Just the Quench Pad is removed about the height of the dome on the piston. BUT keep in mind that the head will be altered but since it's alloy can easily be welded back to closed then machined flat. Alloy makes it fairly easy to machine and weld.

That is exactly what I plan to do, just wanted to run my theory past you guys before I screwed up a perfectly good set of heads, and threw away £800. At least I know it can be done, I'll run 'em down to the machine shop

I figured it was better to leave the heads as closed chamber and make the pistons flater. That way I could get the perfect piston to head quench more easily. Otherwise you are relying on lots of measurements and if you get one wrong....

I see your point Dave,I will have to have a good think about this one