Another broken crankshaft - I'm gonna cry.

[Michaeljp86]

The 6.2 heads will give you better fuel economy, and you will never notice the little difference in the 6.5 larger pre cup holes. Use the 6.5 injectors and lines. The little 6.2 that is now 6.3 liters because of the .40 over size pistons will be just fine.

Wasnt the 6.5 heads stronger because its a turbo?

I have seen turbo 6.5s with 6.2 heads but I always heard the 6.5 heads were built better.

 

[Slim Shady]

Wasnt the 6.5 heads stronger because its a turbo?

I have seen turbo 6.5s with 6.2 heads but I always heard the 6.5 heads were built better.

The turbo heads had larger pre cup holes to get more power. The power difference is minimal. The fuel economy far outweighs the slight increase. You can run the 6.5 heads if you like,the 6.2 heads will be just fine though, and they are brandy new. The newer heads supposedly have better cooling passages, but the motor was just rebuilt so I suspect they have upgraded parts in it. Your choice either will work, feed the turbo oil through a teflon supply line from just above the oil filter housing (pipe plug).

 

[mitchedo]

Fuel + air = power. All else being equal, the reason the 6.2 heads give better fuel economy is because you get less power. If you slap on a turbo and the pump offa 6.5, won't the fuel economy go down anyway? As for power, you may only lose 20 or 30 ft-lbs, something you'd never notice, but is that what you want?

Me? I'd put the 6.5 heads on, no questions. I think I'd miss the 20-30 ft-lbs when I put my trailer on the back and head up the mountain.

 

[midniteplowboyy]

Snap us a pic of the precups on the 6.2 heads. The 82 6.2 heads are different, all the rest are basically the same except for cooling passages upgrades and different precups as they added power. I'm with Slim though, I think I'd use the 6.2 heads since they should atleast have a fresh valve job.

 

[tiredsixfive]

I noticed you have a DB2 pump.If you cranked the fuel rate up with a #1 dist plate,it altered your timing drastically due to reduced volume and pressure across the adv. piston.Too much adv and the crank takes a beating.Next time you have the cover off where you turned up the fuel,rotate the pump until the plate # becomes visible in the "window"so to speak and see which plate it has.It will be numbered -1,-2 or -3.The plates are usually sized with the transfer piston diameter,thus not altering the timing as much with the higher # plates.

 

[tiredsixfive]

Also,any air bubbles present in the inlet supply will cause timing to adv(drastic) also due to the pressure and volume drop across the advance piston.Block(web) cracking is usually found also with advanced timing,either from to much adv,or air entering the fuel system.sorry to sound like a know-it-all,wrote GM warranty for several years and saw many bombs so to speak.Does it still have the 4911 pump? Your military motor has a 24 volt shutoff solenoid on the pump also.

 

[ShawnR]

I compared both heads today and I cannot find any difference.

Here are the injectors side by side:

They look identical, but my injector socket won't fit on the ones from the 6.2. They have Bosch 902 stamped on them.

Here are the pics of the precups.
Off of my old 6.5.

Here is the new 6.2

Here is an overall of the head that came on the 6.2

And here are boths heads side by side.

I couldn't find any differences at all between the old and new ones so I am thinking that they just put 6.5 head on the 6.2 block. The only info I could find on the "new" heads was ACH stamped in it. No casting numbers anywhere.

I am just going to put on the "new" ones with my 6.5 injectors. I will compare injector lines too and see if there is any difference.

 

[ShawnR]

I noticed you have a DB2 pump.If you cranked the fuel rate up with a #1 dist plate,it altered your timing drastically due to reduced volume and pressure across the adv. piston.Too much adv and the crank takes a beating.Next time you have the cover off where you turned up the fuel,rotate the pump until the plate # becomes visible in the "window"so to speak and see which plate it has.It will be numbered -1,-2 or -3.The plates are usually sized with the transfer piston diameter,thus not altering the timing as much with the higher # plates.

I had the pump replaced by a shop shortly after I got the truck. They "inspected" my old pump, said it was shot and offered to return it to me as a box of parts or install a new one. I have to assume that they also set the timing. I did give it a 1/4 turn up after I installed the intercooler and turned up the boost a little.

Also,any air bubbles present in the inlet supply will cause timing to adv(drastic) also due to the pressure and volume drop across the advance piston.Block(web) cracking is usually found also with advanced timing,either from to much adv,or air entering the fuel system.sorry to sound like a know-it-all,wrote GM warranty for several years and saw many bombs so to speak.Does it still have the 4911 pump? Your military motor has a 24 volt shutoff solenoid on the pump also.

I'm not sure on the pump model, but that will be easy enough to look at tomorrow. There shouldn't be any air, getting into the system, but I am replacing all of my fuel lines anyway. Here is a pic of my little crack in the block.

 

[tiredsixfive]

Ouch! At least you came up with an economical way to get her up and running again.Ive got a couple of the hummer motors in a can.Pretty cool container though.Even an o ring seal and a nitrogen purge bung.Mine were rebuilt at the Maine Svc. Depot.1 even has turbo oil provision.

 

[ShawnR]

Ouch! At least you came up with an economical way to get her up and running again.Ive got a couple of the hummer motors in a can.Pretty cool container though.Even an o ring seal and a nitrogen purge bung.Mine were rebuilt at the Maine Svc. Depot.1 even has turbo oil provision.

That describes it pretty well.I was quite impressed with the crate. Mine did have the oil supply fitting for the turbo as well. It was remanufactured by UNICOR (Federal Prison System). Quite a deal for $500 I thought.

 

[midniteplowboyy]

Mine did have the oil supply fitting for the turbo as well.

Have you measured the bores? Its either the very last 6.2 casting or a 6.5.

 

[tiredsixfive]

I was told it will be a 1992 or later block if it has the oil provision,and that even though it may carry 6.2 casting #s,could be a 6.5.I do not know how a person could confirm this.I sold a couple with no complaints on lack of power or mechanical problems.I sold a motor to a Hummer nut who really seemed to know them.He also said that even though the mil specd pumps arent hi po,they do have heavy duty internals and dist head.

 

[tiredsixfive]

Here are the casting #s..well..computer guru im not..wrong pic..this one says 6.2 with oil provisions..try to add the correct one

 

[North Maine]

The Maine refurbishing center is close to my house... I've heard that the policy for a damaged engine no matter what is to just replace it... then they auction off like 250 long blocks for like 2 grand... yea... kinda crazy

 

[tiredsixfive]

I was looking at the shipping tags,Maine to Hooks Texas,Texas to N.Carolina and then N.Carolina to Columbus Ohio.The motors got thousands of miles and never out of the crate.Does anyone know if there is a difference at all between 6.2/6.5 blocks?

 

[Slim Shady]

From what I have read the later 6.2 blocks were cast for either 6.5 or 6.2 depending on the application, the engines were bored to the appropriate spec. The early 6.2 did not have enough meat in the cylinder walls to safely be bored to 6.5 specs.

The early 6.2 blocks also had a higher nickel content, the ultimate being the early 6.2 red blocks (painted red), they reportedly have the highest nickle content of the 6.2 6.5 series. Nickle gave the block it's strength and malleability, so I am told. The early 6.2 heads reportedly also had larger intake valves than the later heads.

 

[tiredsixfive]

Thanks for that info.I havent been buying any more engines lately,so I dont know what the military is selling off right now.Occasionally you will get one of the GEP replacement motors,but out of several,I ended up with only 1 of them.Most do have the turbo oil provision,tube ex manifolds,fresh i/ps ect.My truck (93 2500 6.5 turbo) is getting a 5.9 Cummins as soon as TDC gets his mounts welded up and shipped.I have had great luck out of my 6.5,but at 225K,somethings gotta b gettin worn out.The 5.9 is just me wanting to be different,and the donor truck is here with 16K miles.Not even broken in.I have a good home for the old 6.5 though,a 1994 GMC 3500 HD 2wd with a gutless 454/nv4500.

 

[Slim Shady]

Thanks for that info.I havent been buying any more engines lately,so I dont know what the military is selling off right now.Occasionally you will get one of the GEP replacement motors,but out of several,I ended up with only 1 of them.Most do have the turbo oil provision,tube ex manifolds,fresh i/ps ect.My truck (93 2500 6.5 turbo) is getting a 5.9 Cummins as soon as TDC gets his mounts welded up and shipped.I have had great luck out of my 6.5,but at 225K,somethings gotta b gettin worn out.The 5.9 is just me wanting to be different,and the donor truck is here with 16K miles.Not even broken in.I have a good home for the old 6.5 though,a 1994 GMC 3500 HD 2wd with a gutless 454/nv4500.

AS long as the old 6.5 has a good home to retire to. Got to respect the service it gave. ):h

 

[ShawnR]

UPDATE:

Everything is put together and back in. I need some new T-bolt clamps for my intercooler couplings so it should be totally ready to roll tomorrow afternoon. I did end up using the "remanufactured" heads since I couldn't tell any difference between my 6.5 heads and the new ones. My old heads are going to get coated in grease, bagged up and stuck in the back corner of the barn until the truck is gone.

Total cost:
Remanufactured 6.2 crate engine $500
ARP head studs $180
New Water pump (just beacause) $70
Gaskets (heads, manifold, etc.) $200 (I think)

Other stuff that I replaced at the same time:
fuel filter
fuel lines
oil & filter
antifreeze
glow plugs

I am still under $1000 for a complete new (remanufactured) long block.
Not bad in my opinion.

It seems to start awfully hard and does clatter a lot. I am thinking that the timing is too far advanced. I just learned this evening that the timing mark on the timing gear cover might not always be in exactly the same place. That could screw things up since I based the location entirely on the mark. I will compare with my old timing cover and do some measurements.

Am I correct is assuming that I would rotate the pump towards the passenger side to retard the timing? I plan on making an adjustment tool in the morning and trying it.

 

[NVW]

Yes, rotate to pass. side to retard timing. 1mm=2* Leo