looking for .040 over propane pistons 292 cant seem to locate any????thanks in advance

get a hold of Ross pistons

Gary,
I know we talked about pistons for you. I will put this out for other people that see this. https://www.12bolt.com/store/p509/Ross_292_Pistons.html

Tom, you and I have talked about these pistons, and I am going to have to bite the bullet this year and order a set, that and a cam. But just as a matter in inquiry and conversation, is 9.5 CR the most that can be used on a street motor or will something a little higher also work? If higher, say the 10.0 or better range, is that something that is possible to order from you? Or is 9.5 the easiest available choice?

You should be okay with a 10.0 for a street my buddy was running that in his 292 for yrs. So with the right cam you shouldn't have any issues.

Try a Silvo-Lite 3468 HC Hypereutectic piston. It should work well with Propane. It has a small recess in the top of the piston which will allow for a slightly higher than standard cam lift. Increased compression is really only needed if you're running a radical cam that needs to squeeze what's left of the cylinder volume tighter after keeping the intake valve open partway up the compression stroke. The hotter the cam, the higher the static compression ratio needs to be just to get cylinder pressure back up to where it used to be with a short duration cam.
Jerry

As others have said, depends on the cam. I am running a 219@.50 cam and "theoretically" can run over 10:1 compression with 93 octane. I settled on 9 3/4:1 and achieved that between pistons, decking the head and the block. My logic was better to be slightly low on compression than slightly high.

"theoretically" can run over 10:1 compression with 93 octane"
The .050" duration is not the test, it's where the intake valve closes ABDC at nominal duration.

There are too many variables left out to consider this a reliable method.
If you increased the piston to head clearance @ TDC to drop that 1/4 point, you also reduces your anti-knock protection. How far is it now?

If it doesn't knock on 89 run it. My older 250 was running between 13.9 to 15-1 compression and it ran like Hells fire (89) no knock No Ping. And would start with just a bump of the key. But you couldn't shut it off without loading the clutch.
They run much different than a v8 my 396 (12-1) you couldn't get it to start on 89.

It wasn't posted as a "reliable method", just what could be achieved.