Cylinder head problems.

[56pan]

I put a new mil. surplus engine in my '93 C2500 about 1 1/2 yrs. ago. Had 21,000 on it and the dr. side head gasket started a slow seep of anti-freeze done the side of the block. Also, got bubbling in the coolant reservoir on shutdown. No anti-freeze in the oil. Pulled the head yesterday, and noticed I've got different pre-cups on each head. One head had the 14525518 - 3 dot - 6.2L "J" code and military - 1982-1990 pre-cups, the other head had the
10230426 - Square - 6.5L "Y" code (and presumably military) NA - 1994-up
pre-cups. I was told it was an NA mil. engine when I bought it, and have read that the NA pre-cups will crack on a turboed engine, and every one of them have cracks. Some exceeding the 3/8" limit. I am taking the heads for a valve job tomorrow, so guess I'll have to eat the price on 8 of the 10183926 - Diamond - 6.5" "F" code - 1997-up pre-cups. These are the correct ones, right? Also, while I've got it down, I was considering one of the A-Team turbos for the 6.5, and was wondering if anyone here had any experience with them. The only mods on my truck are a less restrictive turbo downpipe, a mandrel bent exh. crossover and header wrap on both of them. And I've turned up the fuel screw 1/4 turn. Any input would be appreciated.

Thanks.

[Robyn]

The MIL surplus engine, from my experience, depending on a lot of factors, including where it came from, and who the seller was/is can have any amount of anomalies.

From What I have heard, the field shops (war zones) only do light maintenance and not major engine work, and any engine with a serious issue will likely be replaced with a fresh one rather than see internal work.

This said, the likelyhood that the engine you bought was worked over by a shop stateside after it was released by the MIL, for sales as surplus.

There have been a butt ton of these engines released for sale in an AS IS WHERE IS CONDITION.
Many shops over time have bought these engines and resold them after doing whatever repairs were needed to get them more or less sound again.

Many will have had head gaskets replaced, heads, a piston or two and whatever else may have been needed to make them run again.

I personally have seen a lot of these engines sold at auction and have never seen any that were "new/unused" but instead were used with issues.

This does not mean that new ones were never sold, but if you have mismatched precups, then the thing has been into, as the factory would never assemble one with mismatched precups.

Be sure to examine the decks very well to be sure that you dont have a crack from a headbolt out to the outside of the block.
Also examine the decks for erossion where the fire ring sits, as this is common too.

Good luck and keep us posted

Missy

[56pan]

Thanks for the input, Robyn. The block has "506" cast in the lifter valley, and the Navistar diamond. Also, the drain hole at the rear bottom of the lifter valley. No cracks in #8 cylinder, and I'm confident the problem was just head gaskets. But I'll check for the cracks you mentioned when I clean up the block deck. Tried and just cannot make out the casting numbers on the rear flanges. The owner of the surplus outfit I bought it from said he always puts a new oil pump on all the surplus engines, plus new bottom end bearings, and takes the heads off to look for any problems. I saw the old bearing inserts, and it was a new engine or very low time. But it had been cannibalized at the cyl. heads, obviously. And my oil pressure was way down below what I'd seen on my old engine as I figure he'd put on the wrong pump, so I put on the higher capacity pump as I'm sure it's an oil squirter block. All is well there, and I put on the bigger oil lines and a new oil cooler. 376 heads, and no cracks between the valves at all. I would be very grateful if anyone who has experience with the A-team turbocharger would offer his/her input, however. Heads going to machine shop this morning.

Thanks,
Garrett

[56pan]

Put two new heads from O'Reilly on the truck. Couldn't get the machine work for changing the pre-cups and a valve job on the old heads done in time for my limited time home. Both O'Reilly heads had the proper pre-cups for a 6.5 with turbo. Installed an A-team turbo and had no leaks anywhere:), all is good. I'm very pleased with the performance of the truck now. Idling, it sounds like it did with the original 6.5 turbo engine, which I attribute to having the proper pre-cups in the heads now. However, I found no GM casting numbers on the O'Reilly heads anywhere, and as they were advertised as "reman", I believe it's not true. I think they're chinese heads, but everything did fit up perfectly. Hard to get away from chinese parts nowadays. Anyhow, life is good with the truck now.