I, have a 6.2 with a blown head gasket and was curious if this is common with the 6.2. I, have had people tell me that these motors aren't very good, but from reading this forum most subscribers seem to have a positive view of these engines.

It is probably not just the 6.2 but GM engines with the spider instead of an intake maniold with the rear water passage. Heat wipes out the #8 cylinder. later engines had improved water pumps and crossovers to help with this.

I have about 230,000 miles on my 1984 6.2L engine and it still puts out max. horsepower with minimum smoke on the emissions test dynometer. From what I have heard is that turbo boost contributes to a lot of blown gaskets plus high rpm from driving fast. The head gets very hot with high speed driving. I was really worried four years ago when my belts broke while on the highway at night and my coolant temperature hit 265 degrees (and it boiled). We will never forgot those great Nova Scotian's that helped us that night!!!

;) I bought the '94 going on four years back with a ?rebuild and fresh pair of heads and 260,000 miles on the clock. Now it's over 305,000 and the only major repair was to replace a cracked piston recently.
I repaired the one piston 'cause it was all that was wrong. The rest of the engine looked good. un worn and not scarred by use.
500 miles later she's taking 15psi boost and performing like a champ. This was the first time in my life that I attempted to disassemble and repair an engine in this manner but it went straight forward and at $500 in parts, well worth every mile I continue to squeeze out of this block.

My 86 with over 200,000 miles on it blew a gasket 3 days before I took delivery on my 03! This motor had a lot of high speed miles on it (4:10 gears) so I wouldn;t be suprised of that contributed to the failure. Sold the truck for $500, that guy sold it to someone I worked with for $1000 (never mentioned the gasket problem) he got it fixed, and I saw the truck pass me last week! Decent motor but doesn't like high RRPM's.

Quantum mechanic: Be careful of those pistons. I have done that before with a 94 6.5. After a tear down to fix the cracked piston I discovered other cracks at the top of the wrist pin bore, hidden from sight. I ended up replacing 5 pistons. 50,000 miles later I cracked another and ruined the block. I think it was probably already starting to crack also. My last 6.5 was put together with 18 to 1 pistons and it did a great job, for a 6.5. No comparision to my new cummins:D As for head gaskets, early head gaskets were prone to failure, GM sued the gasket makers because gaskets were not to GM spec. The new version of head gaskets are very good. Just remember to always use new head bolts.):h

BIG IMMEDIATE PROBLEM!! HELP

86 Surb, 6.2 torn down, two cracked heads (yes, #1 and #8)
Can't find proper 86 head casting #14077162.

Will the 87 head Casting # 10137567 interchange? Found a good used one.

Dennis

The casting # on head #10137567 is from a '92 or later 6.2 and 6.5 (interchanges).

The #14077162 that I just took off with two cracked heads ( #1 and #8 between the intake and exhaust) is impossible to find a replacement for it. No one has the re-cast or re-built for the '86. They all say that too many of them blew and their are no cores to work on.

My question is this: I was told that the ...240 and ...901 were also built for the '86 (along with my ...162)

Will they interchange? (the ...240 and ...901 interchange with my ...162) No one seems to know that?

My advise - avoid the 6.2 like the plague. This is my third cracked head and fourth blown headgasket in 2 years.

This fix is going to be about $2000 for a car worth no more than that. It's simply that I replaced everything in the last two years - radiator $500, trans $1200, rear end $2300, plus tires, brakes, starters (one a year), inj pump $500, etc. etc.

So, again - will the 240 or 901 interchange on the '86 with the ...162 (casting numbers on each head)

Please respond quickly - my Surb is sitting (again ) in the mechanics (at $50 an hour for labor)

Dennis

I surely feel bad for all of the unsuspecting people that have replaced heads just because of the cracks between the valves. 75% of all of the 6.2 and 6.5 heads out there have cracks. 98% of the cracks are not even problems! Most of these cracks are surface cracks only and do not penetrate the water jacket. Replace the head gaskets and head bolts and call it done. You won't be sorry. If you are really doubtfull, have the coolant passage between the valves repaired with the valve guide repair kit.:grd:

I second D.C i have put many heads right back on with cracks between the valves

Most machine shops that are familiar with the 6.2/6.5 heads know that they can place a cheap brass sleeve in the water jacket to keep the head from leaking when it does crack. A lot of shops have been burnt and won't touch them though, and I don't blame them, these engines are NOTOROIUS for cracking heads, blocks, pistons you name it.
Turbo and high RPMs add to the risk, but none of them are safe.

Possibly the best test for cracks in heads is to build a pressure tester. A piece of plate steel the length and width of the head with round holes cut out so that the combustion chambers are visible. Glue a piece of soft rubber to the plate to seal against the head and either clamp or bolt the plate to the head. Next one crossover block off plate must be installed and in the other crossover location install a block off plate with a fitting in it to allow the introduction of compressed air. Limit the air pressure to about 15 psi and place soap solution on cracks and rest of combustion chamber. I got bored doing this because I have never found a leaker! I have been doing these repairs for over 20 years and have faired well.:grd:

Well, I'm $2000 poorer, but two re-built heads on my 6.2 (86 Surburban). Mine doesn't just crack between the valves, it blows the head gaskets all over the place. Before the "jerk" put in used heads ("dah!") This time a fellow said, "I only do both heads - and let's get new/re-built ones) i got two heads with valves for about $800.

As usual, it was cylinders #1 and #8. I KNOW (I'm pretty sure) that the problem was the cold injection of zero degree water suddenly through the rapid opening thermostat and injecting into #1 and #8 which are the two most vulnerable to getting hot - and (it seems to me) to be missing enough bolts around those corners (front driver and back passenger if I remember right) It always happens in dead winter when the radiator fluid is probably zero degrees.

Another problem was finding the right casting. There were three castings for around the year '86. Mine was the 14077162. There are two different valve sizes (but don't have that written down) I found a good source for, what looks like excellent re-built heads. Contact me and I give it to you. The GMC dealer wanted $1100 per head - and that's without valves and not installed. I got two w/ valves for about $800.

I hope I have a good engine now. I'm not going to put a thermostat in it this winter. I'd rather run colder than to have that same thing happen - suddenly cold water injects (I watched it on my guages!), then the head cracks where it is the hottest.)

This summer, without the thermostat it's running about 160 degrees.

No more 6.2's for me - this is the third time I've replaced heads/ head gaskets, but first time for actual re-builts, not "used" from a junk yard.

Dennis:rant:

The 6.2 is a good, dependable, long-lasting engine. As long as you use it as it was intended....light duty, fuel economy with some towing capacity. Most failures come from over-reving, over-loading and over-boosting! Remember, it was designed as a light duty engine. The factory never installed a turbo on the 6.2 and never intended to do so. That's why they switched to the Duramax. When you exceed the design limits, things fail.

Now two new head - $2000 for re-builts ($800) plus labor. My problem when the head gaskets blow there is not that much of a "sign" they are blown - except a bubbling in the cooler overflow. But, when the heads come off the gaskets are a total mess, the heads are burnt from the exhaust blowing out - in short, a mess.

It's obvious in looking at the head and the block that where these engines blow gaskets there is a shortage of head bolts - they blow right where another bolt on #1 and #8 should have a bolt. Is that where the 6.5 strengthened the system? Also, the cold water (always blows in zero weather) suddenly entering a hot engine at #1 and #8 may be the cause for the crack between the two valves. i've seen the temp gauge suddenly go from 200 back to 100 when the thermostats open (3 different ones)

I now run my 6.2 without a thermostat - and let it warm up.

Dennis

I will say it again, most of the cracks between the valves on 6.2/6.5's are only surface cracks and are no cause for real concern. I just helped a fellow DP member replace his head gaskets on a 93 6.5, lots of cracks between the valves, it is back running with no problems.
The biggest problem with replacing head gaskets on 6.2/6.5 is use of new style gaskets vs. old style and ALWAYS replacing the head bolts with new bolts and very carefully torqueing them. I always go around the head bolts twice with the 50 lb setting before torqueing to 90 degrees. Also, the head and deck surface should be carefully cleaned and scuffed. I like to use 100 grit wet dry sandpaper on a chuck of steel to get a good clean straight surface. Then clean all surfaces well with brake clean. Over heating an engine is a very easy way to fail the head gaskets because the head bolts will yield. Keep the temps below 230f. Put your thermostat back in your engine! You are doing way more damage with it out than you can imagine. 6.2's always have coolant flowing through the engine to the radiator, even when the thermostat is fully closed, return line from heater core runs to radiator. Buy a good quality thermostat, stock gm or Robert Shaw only and your temp won't fluctuate like you say. Most gasket failures are from the fire ring on the front or rear cylinder to the water jacket right next to the fire ring. Late model 6.5's have the exact same configureation, just use better head gaskets than early 6.2's.:eek:

I don't understand why very cold coolant is entering your engine. A thermostat opens VERY slowly unless you have removed the crossover hose between the the coolant crossover and the water pump. The crossover lets the coolant flow past the engine side of the thermostat so that it will open.

The coolant flows thru the heater, then to the right side of the radiator, to the water pump, and then into the engine. The coolant also flows from the crossover to the water pump and then into the engine. These two flows occur anytime the engine is running since the heater shutoff does not shut off the coolant, it just closes the door so the outside air doesn't go thru the heater. Ford's had the heater shutoff valves, but not Chev.

I installed a mod. in my cooling hose so that I canput the flow from the crossover hose into the water pump or into the radiator. I always have the coolant going to the pump in cool or cold weather. In the summer, I flow the coolant to the radiator and it does improve the cooling capacity by 15-25 degrees. I try to keep my coolant temp. around 190-200 F. If it goes over then I divert the coolant to the radiator. If my temp gets to 225 F on a ong or steep grade, then I downshift to second gear.

I've been the last two winters in SE Ohio (from Florida and Arizona). Two winters now (with three new thermostats - Napa usually) I've WATCHED the temperature go from 190 degrees and drop suddenly 50 degrees - in the very, very days. And, it's during these times that I get the cracked heads and blown head gaskets (3 times in three years!)

I'm not sure the damage that would be done running at approx. 160-170 degrees rather than 190 - 200?

I notice truckers having "bibs" (whatever they are called) that open and close partially on their radiators in winter - that must have something to do with this, eh?

Dennis

Hate to say it but napa thermostats are sub par for a 6.2. You need to run either stock gm or robert shaw thermostats. They are a different design than the one size fits all thermostats that the parts stores sell. Autozone or pep boys used to sell the robert shaws or give kennedy a call, he has them. I live in Wyoming and I can guarentee you that we have some of the severest tempature extremes in the country and in the winter with a thermostat you are lucky to get to 170 with the thermostat closed when it is -30f! Sounds to me that your thermostat is opening and closing all at once instead of gradually the way it is supposed to. I have never had head gasket issues unless the engine has lots of miles, the boost has been run too high and too long or the engine was overheated. A severe overheat will almost always result in failed head gaskets as the bolts tend to yield.:eek:

with what DC said, use good(robertshaw) thermostat. did you use new head bolts and have heads checked before install. thermobulbs are designed to read water air no matter how hot will read cool, which could account for temp drop. with no thermostat water flows too quick to pick up heat from block which could also allow heads to lift from not giving heat to coolant, engine oil has to act as main coolant and really starts to kill engine. if you insist on no thermostat get or make restrictor like moroso sells to throttle water threw engine. in winter without wrap(bra) i have put cardboard or plastic in front of radiator to conserve heat, have to watch to prevent too much restriction to cool engine.

Do you have the coolant by-pass hose (from the crossover) to the left side of the water pump installed? If both are capped then your thermostat doesn't see the normal build up of coolant temperature as your engine warms up. Hot coolant finally gets to it and then the thermostat opens wide open just as you are describing.

The outlet on the right side send coolant to the heater and then to the right side of the radiator. That coolant flow doesn't cause coolant to flow past the thermostat.

Thanks Gentlemen for all the hints and info. I will do what you suggest - I see nothing that I can't do in what you tell me. Even now in slightly cooler weather I am not attaining decent water temp. I can see why that would not be good.

Yes, we put in new headbolts this time, re-built heads, GM head gaskets (mechanic said they "update" the head gaskets to fit the needs???? He charged about $125 just for the gaskets themselves. Is this reasonable?)

Another starter went out - this one only lasted 3 months. I entered on another thread for that. I'm convinced two powerful batteries "juices out" the flimsy NAPA solenoids - all the signs of solenoid failure - on this my 6th starter in five years. I got "lifetime" starter, so I don't have to pay, but...(I'm too old for this stuff anymore - tho' I can replace it in my sleep)

I'd like to boost the power by an injector "tweak" but don't know which way to turn the mark. Is it by ear only? Since injector re-build it lost power - struggles up a hill. Does it lose milage to gain power? By how much?

Thank You,

Dennis

Hate to pick on Napa again, but their electrical parts leave a lot to be desired. If you want a starter that will last, get a gear reduction starter A/C DELCO new or rebuilt, from a 6.5.

Thanks again for all the info. I decided to go with the a/c Delco gear reduced starter - and ask NAPA for my money back on -if I get one more - 5th starter in about 3 years.

You recommended a later model gear-reduced Delco from a later year 6.5. NAPA will be of no help to me there.

Do you have a specific ID # or description to help me find one that mates with my
'86 6.2? Everything is closed today, but tomorrow I will need to replace it. It finally "ground" to a halt 25 miles from home yesterday. Poop!

None of the super stores had the Robert Shaw line of thermostats - AutoZone, etc. I will go to the GM dealer if that is the option you suggest, eh?

Thanks again, I hope I hear back today re: the starter info - otherwise I must go for another "FREE" replacement of junky starters.

Dennis

Well, I got the later model gear reduced starter in, adapted my bracket - they didn't have one at local GM.

The starter binds. I put one shim in already - still doesn't want to go in and mesh . Sometimes keeping clicking starter switch gets it to go in.

Or, I go underneath and loosen the two bolts, get in and turn the switch, it meshes, then tighten. I'm going to put in another .20 shim. Will that do it?

They are ordering a GM thermostat. I can see where it is necessary.

What is the "box" starter someone was talking about for this Surb?

One more question : I can't find a thread about it. Will fuel oil work as a diesel fuel? Just needing anti-gel in the winter? Or are there other essential "stuff" in there?

Thanks for all the help!

Dennis

I put the gear-reduced starter in my 86 6.2, but it usually won't engage - just clunks. I have to turn the flywheel to get it to engage.

Can I put 3 (three) .20 shims in it?

Any other suggestions?

Dennis:help:

Friends,

I'm having a hard time getting an answer to this question.

Now, I put in the starter you suggested (gear-reduced), I am up to 3 -.20 shims - and 1/3 the time I have to get under the hood and turn the engine by hand to get the starter to mesh to engage.

One didn't work, two did a little better, three a little better yet.

Do I go to four or five shims?

What's happening?

:help: :help: :(

Both of my 6.2's have head cracks. (My pickup has main web cracks, too! Has had them for tens of thousands of miles but I have lots of spare blocks.) No problem as long as you check them closely before installation with new gaskets and new bolts.

OK, you got a gear reduction starter, who made it? There is a reason I say buy A/C Delco. 1) They don't surface nose housings, they use brand new. 2) I have never had one that didn't work properly. 3) As a professional mechanic, I have to stand behind my work and customers don't like paying for labor to replace faulty parts numerous times. And in case you didn't know it, Autozone carries the A/C delco line, but they might have to special order it. At the very least, I would return the gear reduction starter you just purchased and have them replace it. Three shims is too much.

Poop! You ever been so tired that you just want to shoot the thing?

This will be the sixth or seventh NAPA starter. They didn't want to give my money back this last time - they special ordered a gear-reduced starter - but, I'm sure its not AC/Delco Remy.

Back to NAPA again - they are nice here, but this is TOO much, eh?

Friend,

Dennis

And thank you very much for your insight and help!

It appears my reply went up in cosmic smoke.

It said, in essence, "Thank you so much" I appreciate your comments and help. This will be NAPA starter # in five years. I agree three shims indicates something is wrong.

They special ordered it, but it's not AC, I'm sure.

I'm so tired!

Dennis