You are wasting your time trying to fight for quench.

Leave the combustion chambers big. Stick the piston out of the hole as far as you need to. I'd have to look to be sure, but I ended up at .050-.060 out of the hole.

How do the stock eliminator guys get quench with 8.5:1 and open chamber heads? Even the 10.5:1 guys don't get the kind of quench you want.

Get the chamber correct, with the right valve job and a good top cut, get the compression where you want it and let it go.

It's a pepper and fly poop deal.

iirc the recesses were ~.120" deep as is on my SB 308's. I did not go for quench on that build but wanted to get a rough baseline on how deep they were (& as you know it'd be more after machining to level/smooth/equalize em).

Has anyone ever gotten the open part plasma sprayed to fill them in and then deck them? I know it's probably not cost effective but could be if someone already had the heads (I think the OP is using W2's?). Cadorath Aerospace in Winnipeg does plasma spraying and they're known for doing it well in the aerospace business (they were when I worked there 15 yrs ago)

Unless you are racing in a class requiring stock heads, it is really easier to just get closed chamber heads and run flat top pistons, plus the new heads will flow better too.

I did this many years ago with the KB-232 pistons. I think these were really designed for a Magnum engine with the narrower rod ends?
As mentioned, rod ends need to be narrowed to 1", the heads and block milled to get the correct quench clearance, cylinder head chambers normalized to the same cc's and the "eyebrow" between the valve and quench area needs to be reduced, or the pistons clearanced for it.

I must have missed the .085 quench pad ??? I know nothing about that KB piston .

One other thing I don't see mentioned is how deep is the open part of the chamber in the heads ... at least I didn't see it ??? .... were they machined to be all the same? If you think they are all the same ... chamber to chamber ... AS CAST you couldn't be more incorrect. doing that is the biggest, and most important part, of the whole job.

Research other brand pistons CP Height and stick them above deck, you can also put chevy rods in the mix if you cut the crank down.

You can also hunt for older,but heavy domes pistons.

I'll measure them today and report back.

Alright so I measured all the chambers quench pad, they were all in the
.078x" range.

.078 + .039 gasket = .118" quench

.118 - pistons @ zero deck + .080 piston quench pad height = 0.038"

Is that good? I know its a roughed in & final machining will make it more
accurate.

You would need to mill the OC recesses smooth/equal then mockup a piston/rod in each corner then measure to see how much needs to be milled off of the piston plateaus or the block decks to get that .035-.040 clearance EDIT & keep in mind the thickneses of available gaskets. plug it in to an online calculator to get the SCR as close as you can to where you want it & still maintain quench

Thanks

What is the RANGE??? Did you measure front to back and inside to outside?

It needs to be the same across the chamber and the same chamber to chamber.

When I did it I set the heads up in a Bridgeport and machined each chamber flat. I had an NOS 452 BB head that was .110 out at the ends and the center of the head was .125. The first 2 times I did heads I freehand cut them, what a pain cutting that arc in 2 axis . The last set I did we had installed a Prototrack(CNC) on one of the Bridgeports and that made my life easier.

The heads should be surfaced first so you know it's flat if you chose to machine the chambers inside of attempting it by hand. You also should use a radiused cutter, you don't want the edge of the chamber cut square.

You'll probably have to have the heads surfaced again if it takes a fair amount to get everything flat because it will make the chamber CC larger.

You'd have to really want to use open chamber heads to go through all that, being that the OP is building a small block and the Enginequest heads are so affordable it would be a natural choice for me, zero deck it, .040 head gasket and be done! Being able to use SBC roller rockers is another great benefit

As I posted earlier, the OP is practicing mental masturbation with the quench deal.

There is ZERO benefit to running a SBC rocker arm. Most Chevy guys don't use them.

The correct way to do what you want is outlined above. If you tested the two combos side by side, with compression equal, the tight quench engine might be, maybe 4-5 HP more, but I highly doubt that.

@ madscienctist; not looking for horsepower, just no knocking w/ iron heads & 10.5:1 cr running on 91 E10 swill.

@ JohnRR measured the quench pad in the chamber across 3 points.

@ GTS340.. yeah no way I'm using a Magnum head.. let alone POS SBC rockers.

Don't need quench to run a 10.5:1 360 on pump gas. Been doing it for years.

Correct, they sell race gas at the pump ...

10.5 with iron heads and no quench on 91 octane .... Ok ...

No, not really , using what I had because I already had too much money tied up in them to just toss them in the scrap heap ...

Dang.. learn something new everyday.

Thanks gents!

Just asking, is there enough quench area in the head to justify using, looks kinda small to be effective.? Is there a formula for bore size to quench size?

Here's a video. Motor has gone a best of 11.49@116 in the car in my sig.

https://www.youtube.com/watch?v=iyjFpyQ1ASI