Smoothing combustion chamber

[Joe 1320]

I'm doing the port and polish of some stock iron heads, how much unshrouding of the spark plug is recommended? It seems like the back side away from the valve has a pretty good lip that could be blended. How much should I take out?

 

[bruce]

Originally posted by Joe 1320
I'm doing the port and polish of some stock iron heads, how much unshrouding of the spark plug is recommended? It seems like the back side away from the valve has a pretty good lip that could be blended. How much should I take out?

YOU DON'T WANT TO CHANGE THE SHAPE.

All you want to due is lessen the surface area. Just use a fine stone, and remove the sand appearance. Carbon will form and be the final surface, so polishing isn't necessary.

Then you want to just, JUST, break the edge where the chamber meets the head gasket surface, so there is no sharp edge.

Just do a little blending around where the machining for where the valve sets are.

Taking too much, is worse, then anything.

YMMW.

 

[Joe 1320]

I won't change the shape of the chamber. I have already smoothed the chamber the way you described, I was just thinking that the lip behind the spark plug could use a little blending.

 

[Ormand]

Unshroud the Valves!

There are some photos in the Buick "Power Source" book which show how the chamber should look with the valves unshrouded. Be careful, don't take too much. The "squish" area helps to induce swirl, and to prevent knock.

 

[OneLethal87GN]

OOPS!!

I bought some used heads from a guy to practice on and I smoothed the whole combustion chamber. I had heard it was best to smooth it to get rid of any hot spots that may be caused by bumps in the casting. Sure wish I had some ported heads for my car though.

 

[G-Racer]

A properly polished combustion chamber is a good thing.
Did you say you needed some heads ported?

 

[OneLethal87GN]

That totally depends on how much they cost to get ported. I'm just a po li'l fella.

 

[WH1 85]

I have a set of spare 8445 heads that I plan on doing a little port work on as well. Does any one have any pics of their chambers after the did a little work on them.