D Slater-fire crater advance

Or anyone else who is knowledgeable about the subject. My Super M had IH fire crater pistons in it, along with 22 L stamped on the plate below the weights -- I assume this means 22 degrees advance which is supposed to be used with fire craters. The unit is worn and sloppy, with very little noticeable movement from the springs. I am going to replace the whole mechanism, which is still available. Question is--I have a Tisco sleeve and piston, kit with what I will call imitation fire craters with a much lower step than the original meaning less compression. The original pistons are scratched, but the machine shop person says they can be cleaned up and used with the new rings and sleeves. Only the pistons will be used, bushings, etc will be replaced. I need other opinions on that, agree or disagree, AND if it is not a good idea do I still use the 22 degree advance. I assume the 22 degrees is for anything but the original flat top pistons but I need conformation, to know what advance curve parts to order. The 22 degree weight kit part # (not in the parts book) is 374262R91. external_link changed the number to 362723R91. 374262R91 is in the link. Type fire crater in the keyword, click search and page down to the 7th item, #1014153R1. Thanks in advance.
fire crater distributer

374262R91 was a distributor shaft, 2 springs and the pin for the distributor shaft gear all under the one #. Parts are sold individually now.
Shaft 362723R91, springs 372785R91, and the drive pin 70916202.
If the firecrater pistons check out okay I use them with new sleeves. Figure there made out of better stuff than the replacements.
If decided to use lower compression and the tractor never worked hard the 30 degree original SM advance could probably be used. Looked for a note of the advance rate springs used with the original 374262R91 kit. Didn't find where it was at the first look.
Yes the L22 means the distributor will advance from 0 up to a total of 22 crankshaft degrees if everything is correct. In case something was off a little IH wanted you to play it safe and set the time at 22 with the engine at full RPM and let the low speed time fall to around 0.
Templet to mark the front engine pulley for 22 degrees was in a firecrater kit.
Think I can get a NOS distributor shaft at a lot better price than a dealer if you decide to replace.

Thanks, I'll get back to you, just don't know when. The one and only machinest in my home town, left and then came back, by then he was probably 3 months behind. So, I took the engine to a guy that has his own business outside of town and works when he feels like it, he's had it 6 months. Took it there because I broke off a head bolt and made a mess when I tried to drill it out (never again). Dealer price for the shaft is about $165, springs $44 each, pin $3.00. At first I thought the whole thing was $165, that makes it about $260. Other question is will the 22 degree advance curve be ok with the Tisco stepped head pistons? If so, I might make a deal with you.

Sure the 22 will work. Don't know if thats the best operating setup for those pistons or not. So far I haven't used a tisco piston in a tractor I have. May have to one of these days. Probably the 22 is the safest. Have removed several tisco that swelled and gauld after they were run to hot.
Coarse I don't know if they were installed correct to start with and found other types damaged also.
They have ridiculous prices on the distributor parts. Someone is selling a look alike IH distributor aftermarket for less than $300. Don't know about the quality or advance. They say the same unit fits to many tractors to have the correct advance rate for all.
If you get a new shaft the pin hole for the drive gear will need drilled.