Checking used heads

[Scott Nixon]

My 89 6.2 with a turbo system off of a 6.5 finally coughed up a head gasket (150k on the block, about 10k of that with the turbo).

I have the donor 6.5 block dripping grease in the corner of my garage. Unknown miles, heads look like they were swapped? (Slightly less greasey than the rest and a sticker on the back of one of them).

Figure I'd swap heads while I'm at it. Yanked them off (heavy suckers!), but not sure what to look for. I didn't see any visibile cracks and the head gaskets looked fine.

Are the usual cracks easily visible? Do I need to remove the valves to see the cracks? Should I take them somewhere for magnafluxing?

Thanks for you're help, it's my daily driver and I can't be down for long. Limping along as it is with a radiator full of Thermasgasket and my fingers crossed.....

[ZZ]

I'm sure the only safe way to check them is to have them magnafluxed (sp?) at a machine shop.

[john8662]

If they're cracked, you'll see.

The MOST common type of crack is the small short crack that will appear between the valves. It will be directly in the middle between the intake and exhaust valves. These cracks will be visually identifyable w/o magnaflux, just wipe down the surface with a rag and some brake parts cleaner or carb cleaner.

The second type of crack that is common is the type of crack that starts at an exhaust valve and makes it's way accross the surface of the head. These cracks render your heads as great weights to use in the back of the truck on that icy day.

J

[Scott Nixon]

Thanks!

I thought there was a crack that happens inside the intake passages through to the water jacket???

[john8662]

I have known of heads that have cracked in the intake ports into a water jacket. These cracks were not cracks but casting imperfections, and have been seen mainly in the Chinese aftermarket casted 6.5 heads that ACH sells. Besides that, I haven't seen any.

If you find one head that has a crack between the valves mentioned above, you have two options. You can either ignore the crack (as it will most likely not leak) or install a sleeve kit in between the valves in a coolant passage (best route for peace of mind).

J