I'm working on a pair of '302' heads to be put on a 0-deck KB-pistoned 360 engine.

Since the bores of the 360 are larger than the chambers of the 302-heads, I'm wondering what to do on the chamber edge.

Considering of doing just a tiny rounding off to prevent hotspots and keep as much (quench) edge and CR as possible, or...
...put a nice chamfer and try to unshroud the (stock) valves in the chamber?

The heads are polished and ports are manually/optically contoured/flowed.

Engine will be run on propane with a mild Compcams XE256H cam and 1.6 rockers if the PtV distance allows it.
Shooting for good MPG and low-rpm torque is the goal of this build.

What's advisable?


(I forgot to take pics of where I marked the headgasket outline on the heads to see where the 360 bores end up. Will post them later.)

If it were me I'd scribe the gasket bore to the chamber side of the heads (based off the dowel pin holes), and then chamfer any corners exposed. That's the best you can de aside from ginding away a bit of chamber trying to loose the edge.

I bevel the one side back where the valves
are to unshroud them(both the intake and exhaust
so it helps with the lower lifts... then just a
slight bevel on the rest of the chamber so you
dont have any shape edges.... but with the bevel
near the valves I will give up a bit of compression
to help the flow for the low end lift... this is a
pic of a set of W-9s.. this set was done by Chapman

I will clearance around the intake valves where there seems to be a lot of unneccesary material shrouding the intake valves near the edge of the chambers.
Don't want to give up too much quench area but I tend to agree the unshrouding will be of more benefit here.

Pic of the head with the chambers marked with a felt marker.
The outside of the circles defines the headgasket edge, which ofcourse is just a tad larger than the cylinder-bore.

Make sure the gasket is similar bore to the block, otherwise put a couple bolts in the block and head, flip the block over to use the actual bore for you line to chamfer out to. Also on those 302 heads the pointy thing is really bad hot spot, grind it down a lot to look more like a magnum head. I would also mill them to get as much compression as possible for the propane, it is very high octane and low BTUs so this should help with low speed TQ and MPG.

Check on the block. I matched the headgasket with the block first before I marked the contours on the heads.

I've rounded off the pointy nubs in the chambers already a bit, but they'll probably be semi-removed anyway for unshrouding the intake valve and I'm also thinking of making a quench jet groove in the quenchareas, pointing at the plugs.

The heads have been milled once already.
I plan to mockup the engine first and see when I'm at with the compression ratio.

With the (pretty much) 0-deck KB-pistons a CR of 10.5 to 11:1 should be possible. Although I don't want to push my luck too much with going too high.

11 to 1 would not be too much, actually still low for propane. I would shoot for 12 to 1 personally but that won't happen with the parts you have.

This - most times the head gasket dia is considerably larger than the bore.