I have owned a 94 Gmc 3/4 ton 4X4 with the 6.5 TD since last may. Had 107k on it when I bought it, now has 118k, blew head gasket.

This is my first diesel, have had gm trucks since I could drive, 30 years now, never had a major engine failure.

Pulled the heads and found where the gasket blew. Had the heads cleaned and magnafluxed, they are cracked between the valve seats, Junk.

Rebuilt heads are $750. New heads are $1500. Motor has enough blow by to push out the dipstick. Lots of oil in the turbo and intake manifold. Could be turbo seal I'm told, as well as blowby. Has 20k on new warranty replaced injector pump. Has 30k on new tranny. Both done before I bought truck.

Truck ran ok before the head gasket blew, 18 mpg, used about 1qt of oil every thousand miles other than that no complaints. New Gm 6.5 long block with 3 year 100k warranty is 6 grand.

Not thrilled about putting new heads on a lower end with 118k on it.

I'm assuming the new GM engine has had some improvments done since 94, would like to find out what they are. Have been advised to stay away from rebuilts.

I've got 6 grand in the truck as it sits, looking for some opinions on what to do. Thanks

J Benton

If it was me i would want to do everything i could to get it up and running again, but if u want to take the cheap way out you could always drop a 350 in it

if u want to take the cheap way out you could always drop a 350 in it
traitor...

Ebay has heads rebuilt for $275 and new for $350 iirc. That's not many miles. If you have the engine out, you could make sure the bearings are good.

K-line sells a brass sleve kit for the cracks between the valves model KL3900. You pull out the 7/16" freeze plugs on the intake port side, ream out the passages, and install the sleves with loc-tite using the insertion tool. The kit comes with about 50 sleves, reamer, sleve guide, insertion tool, cleaning brush and loctite 609. The only other thing you need are the 7/16" freeze plugs. The # I have for them is 1-800-824-5546.

Those cracks are "normal' for the 6,5 heads and usually do not go clear thru to the water passage.

The kit suggested by lupey is the fix for your heads

I forgot to mention that a lot of companies selling rebuilt heads for these things install these sleves as part of their rebuild weather they are cracked (yet) or not.

traitor...lol, no i hate this idea, 6k is a lotta dough though, although i think you can get em a lot cheaper than that. P.S. before id put a 350 in mine id leave it settin till i had the money to replace or fix the current engine or put it towards a dmax:ro)

I would say that 90% of the 6.5 and 6.2 heads I have had apart were cracked between the valves. Years ago I made a plate to pressure test the heads. I stopped doing it because I never found a set that leaked! Unless I see traces of coolant on the cracks, I run em the way they are, and have recommended this to countless people and never had a comeback. If the heads are cracked anywhere else, then you need new heads. The head gaskets do blow, no big deal. What do the cylinders look like in your engine? How much ridge is there? Unfortuneately many people buy used 6.5's with fairly low mileage and assume that the engine was maintained well. Running the oil for extended drain intervals in a 6.5 will kill the engine. Even just running the oil for 5000 miles like is recommmended in the service manual is not good. Too much soot and the soot becomes an abrassive and the cylinders wear.6.5's that don't have excessive taper can be successfully re-ringed and will run good and it doesn't cost an arm and a leg.
Most 6.5's that you hear about that go over 300,000 miles have had very good maintainence and usually had oil changed about every 3000 miles.

If you didn't have cracks between the valves on your heads then I would be worried. :) Those cracks are completely normal for a 6.5 TD and completely cosmetic. Just go ahead and reuse the heads.