boring a T block

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rich from pec
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boring a T block

Post by rich from pec » Mon Jun 01, 2020 7:56 pm

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.


Jerry VanOoteghem
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Re: boring a T block

Post by Jerry VanOoteghem » Mon Jun 01, 2020 8:18 pm

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.


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rich from pec
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Re: boring a T block

Post by rich from pec » Mon Jun 01, 2020 8:36 pm

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.


Kerry
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Re: boring a T block

Post by Kerry » Mon Jun 01, 2020 9:49 pm

.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.

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kelly mt
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Re: boring a T block

Post by kelly mt » Mon Jun 01, 2020 11:46 pm

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.


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Re: boring a T block

Post by ModelTWoods » Tue Jun 02, 2020 12:22 am

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 !


Erik Barrett
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Re: boring a T block

Post by Erik Barrett » Tue Jun 02, 2020 3:08 am

.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.


Lonnie Doan
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Re: boring a T block

Post by Lonnie Doan » Tue Jun 02, 2020 4:02 pm

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. :D

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TonyB
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Re: boring a T block

Post by TonyB » Tue Jun 02, 2020 9:34 pm

Against my advise, the block of Lucky 7 was bored out to 0.125”. It seems to work just fine, lucky I guess 😊😊
Tony Bowker
Ramona, California
1914 Touring, 1915 Speedster, 1924 Coupe.

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