Cracked model A block

T

trctrdr

Member
I'm sure this has been covered before but one of the model A blocks I have is cracked through the exhaust seat toward the # 2 cylinder, probably about a half inch long ( hasn't been magna-fluxed yet). Is there a good fix for this or do I have a boat anchor?
 
I'd be interested in the answer too, as my '28 has done the same thing.

Earlier this year, the engine was seeping coolant through this crack into the exhaust port / manifold / muffler, and eventually into the crankcase.

A recent treatment of "K-Seal" stop-leak seems to be holding... ( I know it's a band-aid...)
 
That would depend on how much time, money, and love you have in that particular block, and how much more you want to invest to end up with a patched up block. A blocks are plentiful. If it is just an un-rebuilt core, I see no value. It needs metal stitching, the valve seat recut, cylinder rebored and sleeved, and maybe deck work, depending on the skill of the stitcher. Bad place for a crack, common on rare B blocks.
 
Mike is right. I do these with a new seat installed and bore the cylinder to install a sleeve and stitch the deck surface before I resurface the block This makes the crack all but gone and no more leaks. It is pricey but there is a lot of machine work involved, probably 4 or more hours to do it right.
 
James Rogers said:
Mike is right. I do these with a new seat installed and bore the cylinder to install a sleeve and stitch the deck surface before I resurface the block This makes the crack all but gone and no more leaks. It is pricey but there is a lot of machine work involved, probably 4 or more hours to do it right.
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What if the crack goes down below the valve seat? Those seem harder to fix.
 
Go to a good auto parts store and tell them you want to pin or stitch a block. You will need a special drill bit, a tapered tap, and some tapered pins. If your block has an insert valve seat, remove it. Drill a hole at the beginning of the crack, tap it and screw the tapered pin in with some Loctite. Cut off the pin and file it level with the block. Drill the next hole overlapping the first pin and screw in another pin. By overlapping the pins, they lock together. Continue this process the length of the crack. When you're done stitching the crack you will need to install a new valve seat.

I've done this on a few Model As and once put 40 pins in a straight 8 Packard block. Worked great every time.
 
John Stone said:
What if the crack goes down below the valve seat? Those seem harder to fix.
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You follow the crack with the stitch draw-screws right across the valve seat and down into the port. You then have to finish up with a die grinder and carbide burr in the port and re-machine for a new valve seat insert. Diesel shops do it all the time. Fixing a diesel head crack for $400 plus 3-500 for the head rebuild beats $2500+ for a brand new head (bare) or $1500 for a good used if you can find one. Think model A engine rebuilds are expensive? Try $15-25K and up.
 
trctrdr,

Find another good block with no cracks; why put 3 to 4 thousands dollars in a rebuilt engine using a repaired block. Just my opinion.

Ron
 
It's worth saving but while better blocks are available I would pick up a better one and store trade or sell the cracked one.
 
trctrdr said:
I'm sure this has been covered before but one of the model A blocks I have is cracked through the exhaust seat toward the # 2 cylinder, probably about a half inch long ( hasn't been magna-fluxed yet). Is there a good fix for this or do I have a boat anchor?
Click to expand...

Unless the engine numbers match the car numbers, you would be better off using another block.
The one in my Sports coupe was cracked, but it was the original engine. So I pinned it, put in a seat and cylinder sleeve. I also have fixed many in my Dads garage back in the day when no one had any money for new engines. It's not a big deal but does take a lot of time.
 
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