Head gaskets

[84 Convert]

Ok, now I have two trucks that need head gaskets! I was figuring on doing the one I knew had a problem within the next two months, and now my daily driver surprises me by hydro-locking itself at my work! Three holes with water in them. Any special tips you guys have found especially useful please do share. I checked with the local engine shops and they are telling me that the way they surface 6.2L heads is with a large belt sander. Is this normal procedure elsewhere? The upside to all this is that my daily driver is sitting right outside an excellent shop.

Thanks in advance for your help.

Gregg

[DmaxMaverick]

I checked with the local engine shops and they are telling me that the way they surface 6.2L heads is with a large belt sander. :eek:

I wouldn't take it to that shop. Surfacing heads with a belt sander is a %100 guarantee of another head gasket soon. The heads should be milled and mic'd. I forget what the breakdown is, but if so much is milled, then a thicker gasket is required to maintain deck clearance. This is not to mention the importance of a true, milled surface. The best way is to determine how much is milled off, then compare it to the marking on the original head gasket. If the magic number is exceeded, then the next size gasket is required.

Make sure you use new head bolts. You can get head gasket kits with new TTY bolts. I've used Fel-Pro with excellent results in the past.

[catmandoo]

in my 10 years and over 500,000 miles between 3 different 6.2 and 6.5's i've never had to put in a headgasket or pull an ip but it does happen as for milling the heads i remember the old 5.7 olds used 4 different headgaskets and they were different colors as for how thick you needed there was 2 thicknesses and 2 with bigger bores and on them you could only cut the head 10 thousands anymore and it was junk.

[84 Convert]

Thanks for the caution, Dmax maverick, I had thought that sounded a little hokey... the belt sander thing. Might as well just throw in a new gasket and go! I know that doesn't work... it has been tried(not by me) on the one I was already planning on fixing. As for the never having changed gaskets, catmandoo, the C engine that came in my GMC never had problems of that sort either. Both of these that need gaskets are J engines out of 1-T crew cabs with 4.10:1 gears and of course, no OD. I'm beginning to wonder if there is a correllation between high loads, high RPM, and blown head gaskets. hmmmm...

Gregg

[catmandoo]

sounds like your on to something there that would be interesting to here from others on their headgasket failures and what engines they have.i personnally only use mine for cruising down the road almost always empty.i bought diesel for the milage and again yesterday they raised the price of gas to more than diesel so i'm in heaven again ha ha ha poor gas suckers.

[TimK]

84Convert,

I replaced my head gaskets about 20K miles ago on my 85' 6.2L J engine when I was replacing a couple of cracked pistons. I followed the recommendations and procedures listed in the R&R guide sold by this website. I decided to use the Fel-pro TTY bolts and the 6.5L head gasket. The 6.5L gaskets have an extra hole stamped in them at the front of the head for a water jacket gallery that does not exist on in the 6.2L block. I highly recommend placing a very small bead of silicone rubber on the gasket around this hole. On the side I did do this, I had zero leaks. On the side I did not do this, it had a small dribble of antifreeze when I filled the system with coolant. After all the work it takes to install the head, I was very disappointed to see this. Instead of pulling the head back off, I decided to warm the engine up and cool it down through a couple of heat cylces with the radiator cap loose. This sealed the hole. Here I am 20,000 miles later and no problems.

Good Luck.

TimK

[rumbler1]

I rebuilt my 86 J 6.2 back in March. I had the block resurfaced and needed a .010 thicker head gasket. I installed pistons which were made .010 shorter for just such a situation, but some of them protruded a little too much, so in went the thicker gasket. About 3500 miles later I have no problems. While you're at it have the heads checked. When the shop checked mine for problems they found that all eight intake valves had been leaking, thus the reason for all the black residued around the intake manifold. A tip I got from another DP member on installing the heads: after initially torquing the head bolts to 50 lbs, paint a white line on top of each bolt head about 1/4" long at the edge of the bolt head, running from the edge toward the center of the bolt. This way when you give the bolt it's final 1/4 turn in, you can tell by the painted line just how far you're actually turned the bolt, and if you've missed any. Just to make it aesthetically pleasing I've painted the lines at the bottom of the driver's side and the top of the passenger side. That way when I'm done all the lines are facing toward the front of the engine. Also, it will be a lot easier to install the head if you use an engine hoist to do it. I was able to leave the exhaust manifold on the passenger side when I did it, but had to remove it from the driver's side. Good luck!

[aloharovers]

I did NOT have good results trying to use 6.5 gaskets on my 1984 J 6.2.
They leaked antifreeze from the extra hole in the gasket. I think it was front left and rear right.
Put 6.2 felpro gaskets in and leak stopped.
Pete

[84 Convert]

Thanks for all the info! I am still wondering what sort of procedure is used for machining the heads. Do the pre-cups come out for machining and then get cut down themselves or what? Both the local shops are saying that regular machining like that for a gas head will tear the pre-cup out of the head. Any thoughts? Thanks again for the help!

Gregg

P.S. Maybe I should try a big truck engine shop instead of the car engine shops. No?

[Dieselboy]

When I did my head work, I installed brand new 6.5 "T" pre cups, then had the heads milled. They were still installed when I got the heads back.

[arveetek]

As for head gasket failures:

I rebuilt my '82 C code engine in '95, using new Fel-Pro gaskets, and the original head bolts. I've put over 100,000 miles on it since then, with no problems. I've upgraded the engine using a J intake, Dr. Lee's exhaust adapters, turned up pump, and other things like that. I've pulled my fifth-wheel all over the country, with EGT's in excess of 1300 degrees for miles on end, many times spiking above 1400 degrees. I've kept the engine up near the governor pulling the trailer up mountain passes. No head gasket problems at all.

I don't know what to think. One thing to mention is that I've never had a cooling problem. My temp guage hardly ever gets close to hot when pulling hard.....only when really revving her out on a hard pull. Most of the time it's in the middle normal range. Perhaps head gasket failures are more related to excessive engine coolant temps on hard working engines, or to improper installation during rebuilds?

Casey