8BA block concern

[Mike51Merc]

Before you get radical with disassembly, pull the center bolts and apply Permatex #2 to the threads. Reinstall to normal torque. Let it set up overnight and test it again.


Do a compression test. If the center cylinders are low, then you may have a crack in the exhaust runner that goes up into the valve seat.

Another test is to run the engine with a spark plug removed (one at a time!) in the suspect cylinder. If it belches steam or droplets, you found the problem.

 

[flatheadmurre]

The blocks has a bad habbit of separating in the thread of center exhaust runner...weaping coolant down into the exhaust.
Longer threaded stud and sealer fixes that issue...

 

[3twinridges]

So I started out pretty sure the center headbolt was leaking. As the first photo shows. But then when I go back and look at #7, it looks like it’s wet around the guide but I cannot tell for sure. The block was magged thoroughly so I am surprised by that if it is.

 

[JSeery]

If you're looking for cracks it is best to pressure test the block, mag doesn't get everything.

 

[3twinridges]

We pulled the center bolt tonight and resealed it. Going to let it setup overnight before we refill with coolant. I have the GM seal tabs to add for the leak test.

JB

 

[3twinridges]

Just to update all that responded, we reapplied sealant to the center bolt and let it setup. re-installed head bolt and refilled with coolant. Exhaust leak has stopped so that must have been the culprit.

JB

 

[Bored&Stroked]

Just to update all that responded, we reapplied sealant to the center bolt and let it setup. re-installed head bolt and refilled with coolant. Exhaust leak has stopped so that must have been the culprit.

JB

Great News! That crack is so common that some of us believe that Ford gave it a 'Part Number'! LOL