91 Suburban w/6.2 Head cracked
 

Hey all. Grew up around the 6.2s/ 6.5s as a child and now I own one.

Just purchased a 91 suburban with 267K miles on it.... CLEAN. no rust great paint, garaged all it's life when it wasn't on the road.

Now for the bad part. when I went to look at it (and buy it) I couldn't get the radiator cap off because the surge line/clamp was stuck up under it and I had no tools with me. So, I bought the thing and drove it home...

The next day I took it down to my shop (started hard) and got the cap off. radiator is 1 gallon low.. Refilled and started the burb. immediatly coolant shoots out of the filler neck.... while it was running I stuck the cap on for about 5 seconds and then removed it. when it was removed I got a huge "woosh"...

Narrowed the cracked head down to the passenger side by removing the T stat and looking at the crossover tube.

When it was removed I had to broken lifters on #6, and damage on cylinders #4 and #6 from water... The pistons are pretty pitted up as well as the head. I got the lifters out and the rollers/cam is good, but the guts of the lifters were destroyed and the pushrods were bent. I assume from HYD locking?

Both cylinders show signs that they were rusty and have surface pitting from rust. I'm unsure how much compression I'm going to lose because of this if I don't repair, but on the upside the engine idles without a miss and smooth, so I think there's enough compression to fire.

I don't know weather to replace the other head gasket while I'm here or not. A friend has a good used head off of a 6.5 diesel for me to use, so I figure I'll swap out my injectors and give it a try. May to a complete engine compression check to see how the two cylinders stack up against the rest.

I know the engine has high miles, but I'd like to see me get some time out of it while I look for a spare.

Any suggestions?

The same friend has a pair of used lifters for me as well, and I can't see for the life of me how this engine maintained 40 lbs of oil pressure with the old lifters all busted up like they were.

http://www.prcforum.com/forum/attach...0140326_28.jpghttp://www.prcforum.com/forum/attach...20140327_6.jpghttp://www.prcforum.com/forum/attach...20140327_7.jpghttp://www.prcforum.com/forum/attach...20140327_9.jpg

I can see a cracked cylinder in the last picture at about 7:30-8:00-can't you?

I would say hydro lock pooched the engine.

Is your buddies 6.5 a turbo or non? Running turbo heads on a naturally aspirated engine will work, BUT the precups are different and you may suffer some poor fuel mileage. If your looking for a good used set of 6.2 heads I have a set I may part with. If your interested let me know. I'll have to find out about shipping. That could kill the deal.


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*update*

Got a 6.5 head from a friend for a good deal. came off his 93 6.5 diesel.

I was going to switch out precups until I pulled the drivers side head as a precaution in inspect and replace the head gasket. once it was off I was suprised to find it had a 6.5 head already on it (T precups).

So, I decided to put both heads back on with the T pre-cups since my 6.2 cups were cracked all to hell anyway.


Found out through a friend that he knew the guy I bought this burb from, and he also knew that they had filled it up with gas years ago, got about 5 miles out of town when it overheated and quit them.... that's when they had to replace the fuel system.

Could've also been when they cracked the hell out of the passenger side head.

Yes, there's cracks above both intake valves on holes 4 and 6. one is cracked from the intake valve all the way out past the fire ring. it must have been pushing coolant in there like a garden hose.!:humm:

Regardless, I used a 3 stone hone on those to cylinders to attempt to put some cross hatch back in the holes and cleaned everything up real good. heads are back on as of yesterday (just haven't had any time to work on it) and hopefully tomorrow it'll be a living breathing machine again.


I'd have taken you up on the 6.2 heads had I known sooner. I'll keep you in mind if this engine doesn't pan out.

On a side note a friend of mine knows a guy that just bought an 86 burb for the wheels and tires and wants to sell the rest of it. it's a 6.2/700r4 setup, so it'd be the same as mine. guy said it ran when he parked it.... $400 sound like a decent deal?

$400 is a great deal. If its not all rusted to hell you'll be able to sell parts off of it and get the drivetrain for free. Glad to see your getting ahead of that mess. Previous owner should have told you about it. I take it that the 93 was naturally aspirated since it has the T precups in it already. Should work out good for ya. Good luck and hopefully you'll be up and running soon.


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not sure if the 93 was N/A or not. I thought the "T" cups were for turbocharged units?

I'm not expecting miracles out of this thing, I just hope it starts/ runs and drives well for awhile.

As soon as it's running I'm gonna drop the oil to get rid of any garbage from the failed lifters plus any gasket material or antifreeze that could be present after this teardown.

Got a new set of Kennedy quick head glow plugs for it that I'm putting in at the same time. hopefully this thing cranks right up.:choochoo:

Here are my 162 heads off my 6.2. They have 1 dot on the precups.

Attachment 29091

Attachment 29092

My 567 heads off my 92 6.5TD. They have 2 dots on the precups.

Attachment 29093

Attachment 29094

You can see the infamous crack between the valves on the turbo engine. Although they never leaked.




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yep, I've heard that the 6.2/6.5s commonly had cracks between the valves that rarely leaked. That's why I was so suprised to see the two cracks on this head coming off the intake valves only. the 567 heads I put back on had no cracks at all. both heads have the two dot "T" stamped cups in them. If I had more time and was more confident in how long this engine could last, I'd have shopped around for some 6.2 precups a little harder.

got her started up tonight.

ended up pulling the drivers side head to inspect for peace of mind, and found that side had already been replaced with a 6.5 head. so, I put the 6.5 head I aquired on the bad side, and threw it back together. started up and runs good it seems, although at idle I'm noticing some white haze coming out the drivers side bank... don't know what that means exactly.

time will tell if the two bad cylinders I cleaned up will hold up or not. if I bring the engine just off of idle I can feel a slight miss, so we'll have to see how that progresses.

I'll finish buttoning her up tomorrow and take it for a test run.!
:jump:

Good to hear. Hope it all works out. If its running, that's a good sign.


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good luck, i hope the best for you, maby it will clear up once it warms up.:tu:

See post #2 of this thread.

Started it up this morning again and found that I must have had a little air in the lines yet. once it bled off the thing ran great... I still have a little smoke, out both banks, but it's very light and I think only noticeable because it's in my shop running. No bubbles or compression in the cooling system either.

after it ran about 20 minutes while I did some chores, I cam back and did a cyl cutout test on every hole to make sure there wasn't anything missing. every hole was firing.

I did the test with the advance lever on the pump to see if it was too advanced or not, and when I push the plunger in the engine gets a little more of an aggressive rattle to it. maybe it's advanced too far?

The throttle response of these engines is amazing to me.

What about the cracked block Racer55 is referring to?:humm:

Maybe I am seeing things?
Does that look like a crack to you?

I think it's a crack!

Naw, those were scratch marks.

If the block was cracked I'd still have compression in my cooling system.


I'm gonna take it for a 50 mile trip tomorrow... we'll know by the end of that weather or not this thing will hold it's nuts and bolts.

Give this a read:
6.5 blowing coolant everywhere (Total Rebuild) - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Sometimes it has to have the right conditions for the compression to get past the crack.

ran it 50 miles yesterday. no heating, no smoking, runs strong. Got it home took radiator cap off and had only normal hot cooling system pressure. reserve tank and radiator were still full as well. started it up with the cap off and have no bubbles..

Also noticed that my blowby is much less than it was 50 miles ago. right after I put it together I had a fair amount of it. now it's not much to speak of. the two cylinders I honed must have broke in...

Only thing I'm really noticing now is on cold startup it takes longer for the passenger side bank to "clean up" and get hitting on all cylinders... you can see it in the exhaust that it stays white longer than the drivers side bank. But, that too was before I took it for a drive. it might be better now.

Good deal. The passenger side might need some more run time to seat in. At least your running and not pressurizing the cooling system.


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Hey again guys, the engine's running good on this old burb, but a couple questions-

Sometimes when I go to start it hot the glow plugs wouldn't cycle. however it still started, just cranked longer. so, I bypassed what I thought was the "inhibit" switch? it's the one behind the ex manifold on the passenger side head.

Things had been working fine until yesterday morning. it was 25 degrees and I went to get the old girl started. I cranked and cranked and it smoked and smoked and wanted to fire, but acted as if it wasn't getting the glow plugs, even though the light was cycling... finally it did start, but I'm wondering, did I bypass the wrong switch?

Thanks!

DF

Sounds like you got the correct temp switch. Are the glow plugs good? Maybe they are weak.


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brand new kennedy quick heats

Check the glows for power when the light cycles-perhaps the relay is bad or a fusible link or several are burnt out?

Yes i see the crack in the cylinder as racer55 pointed out time for new motor

This thing I'm wondering now if it's a fuel issue.

found out the switch I had unhooked was the switch for the cold timing/throttle advance. hooked that back up. Tried to start it today at 40 degrees, and same blasted thing. crank and crank. white smoke out both sides till it fired.... once fired up it ran great. Took it to the shop, tested glow plugs. Glow plugs are coming on and off with the light. However, I'm not seeing that the cold advance is working. should the little plunger on the bottom of the IP be pulled in towards the pump when cold? or out? I can move it manually, but I don't think it's moving on its own.

What's strange is none of this was going on until I took it out to the shop the other night to put 2.5 inch lift blocks under the rear springs. since then I've got this cold start issue.

Damn your right, that temp switch is for cold advance. I was thinking for glow plugs for some reason. That would leave glow plugs on until engine warmed up.
As far as plunger for cold advance, can't you jump it and see if it moves? Ground the body and 12v to connector and see if it pulls in or pushes out. I have a couple pics of the cover off my DB2 pump but its hard to tell which way that sucker moves.

Attachment 32712

Attachment 32713

The pen in the pic was referencing fuel shut off solenoid for someone else.

Maybe try running a jumper to cold advance when engine is cold if you don't have power to it and see if it starts easier.


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