This may be a silly question, but here goes. I've pulled the head off of my 29 block and found a crack in the water jacket and several broken studs. I have another block that appears to be in good shape, just missing main caps. my question is, can I just switch main caps and be alright, or do the bearings need re-poured. The cracked block was gone through and has beautiful new bearings poured so I hate to switch.
Main Caps
- Thread starter 58Darlene
- Start date
This subject has been discussed sometime ago, the possibility that the main caps might interchange is slim. The reason is that the mechanic that poured the mains was not careful enough to align the reamer, front to rear in the block, centered and 4.155" from the cam shaft bore. When you bolt the cap on the block it might bind up and the crank wont turn. Hope you get lucky and it works.
carry on nick c
carry on nick c
I've got another block. Doesn't appear to have cracks. All of the studs are out, and not broken, and has decent looking bearings. I just don't have main caps for it. Can use the good one on the other block without redoing the bearings?
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hardtimes
Well-known member
Hey Darlene,
If I were in your position, I'd take the main caps and good crank and try installing them in the 'good' block. I'd lay the crank in and add one main. Test for bearing clearance and when that is right, I'd try rotating the crank several times. Then on to the next main and repeat the process. If at some point, you cannot get proper bearing clearance AND free crank rotation, stop and find reason why. If you get all three mains in and clearances are acceptable to you AND the crank is freely turned..you may get lucky
! What do you have to lose in this process/procedure ?First thing to do is see if your crank fits in the new block. Just try to lay it in.
Then get some measurements on the new block and the old caps. Measure the new block and old caps at the parting line, very carefully. Odds are that after 80 years and who knows how many rebuilds, the caps and block will be different. But whatever, then measure the crank dimensions and compare to the block and caps.
You can get the correct clearance between the top of the caps and the crank by just adjusting shims, but that does not deal with side dimensions. If the cap and/or block are too small for the crank, you may be able to lap them in with Timesaver.
Then get some measurements on the new block and the old caps. Measure the new block and old caps at the parting line, very carefully. Odds are that after 80 years and who knows how many rebuilds, the caps and block will be different. But whatever, then measure the crank dimensions and compare to the block and caps.
You can get the correct clearance between the top of the caps and the crank by just adjusting shims, but that does not deal with side dimensions. If the cap and/or block are too small for the crank, you may be able to lap them in with Timesaver.
Pete
BANNED
The chances are very slim you can use the caps on the other block.
When you go to the machine shop, take all of the parts and let them measure things to see if you have a combination of parts that will work with no machine work, other than digging out the broken studs.
That crack can be TIG welded without distorting any of the machined surfaces if you can find a qualified shop.
They can stipple the welded area when done so that you can never tell it was welded.