MTFCA Forum

Can a T block be safely bored to .080 over or should it be sonic tested to make sure it has enough "meat" left to ensure it won't present a problem later on. The block presently has an A crank with 292 Y Block .060 pistons. I searched the internet and found that .080 oversize pistons are hard to find. Any suggestions on pistons to use.

Some have even been bored to .125. That's where I'd get scared!! Past .060" you can run into trouble sealing between #1 & #2 and #3 & #4, as the wall between them starts to get pretty thin. I think I'd begin to consider sleeving back to standard, or finding a better block.

thats exactly what i was thinking. because its a A crank block, I think sleeving would be the best option. the block is in good shape except the bore has too much taper. I have no idea who did the A crank conversion since I bought the complete engine and transmission at an estate auction in 2000.

.080" pistons are now available when once you could only get them in the high dome ones. Back in the day of the cast iron ones you would bore out to .120" + The thing to remember is the more you bore the thinner the wall and hotter the engine runs. The head gasket at the heat rings between 1&2- 3&4 would be OK on a.080" re-bore.

I'm running .080" pistons, no problems except You will have clearance problems with high compression heads. I had to do some grinding on the combustion chamber of my Prus head to get clearance without a head gasket.

I have two 1926-27 blocks. Both were, or are beyond .080. The 27 has already been rebuilt and was sleeved back to standard. The 26 will go to the machine shop this summer and it will very likely have to be sleeved, also. I have some new .060 aluminum pistons and when I placed one in the top of a cylinder bore, pressing it against one side of the bore, I could see a good 1/16th of an inch gap on the opposite side of the piston. That means that the cylinder is probably in the neighborhood of .090 !

.080” will not be a problem unless there is a lot of core shift in your block casting, which is rare but does happen. I would not be afraid to punch it out to that point, I have built many that large. We have built two full race overhead engines here bored out to 3.879”. That’s nearly.140” oversize. We have had numerous problems with that but none related to cylinder wall failure. It leaves very little between the front and rear pairs of cylinders so we have to run a stainless O ring and a solid copper head gasket to keep it sealed at 10:1 compression. Not a problem with a flathead.

Try telling your T block how much more efficient the newer stuff is. Tell it the 40s stuff has so much more power. Tell it the new 54 1/2 small block Chevy is way easier to work on. Tell it about your heavy work schedule and your mother in law. That should bore it to death.

Against my advise, the block of Lucky 7 was bored out to 0.125”. It seems to work just fine, lucky I guess