2 Strikes and I'm out.

[Aerodyne]

I have two engines a 85 6.2 and a 93 6.5. Both have cracks at the main bearings. The 6.2 is on the scrap truck now.

I found a 95 GMC van type schoolbus at Pullapart with a na 6.5? for 166.00 w/warranty. It will take most of the day to get it out. Is it worth the trouble to pull it out and bring home turn upside down pull the pan to check the mains and rods?

I want to put a diesel in my 46 Ford 1 ton. It has a 80 chevy front clip so I could use the chevy motor mounts. The GM diesel will fit the small engine compartment better than others.

Thank you for any ideas.

Lynn

[Robyn]

Dont toss the blocks unless the cracks go out of the bottom of the bolt holes.
Lock and stitch inserts will effectively repair these cracks easily.

The should be someone in your area that can do it for you.

I do them all the time here.

If the cracks are in the corner of the register then the block is junk though

A goodly percentage of 6.2 and 6.5 blocks will show some cracks in the outer holes of the center mains and unless they are as described they can be fixed in a jiffy.

I do all 6 center outers nomally. Takes a couple hours to do them all.

Hope this helps

[jerry598]

Robyn,
You've mentioned the "register" relative to cracks in the block several times, but I don't have a clue as to what part of the block that would be. For us novices, could you try and describe what part of the block is the 'register'
Thanks,
Jerry

[Aerodyne]

Robyn

Both blocks have cracks at the register where the main cap meets the block.

I still have the 82 C 10 with the red motor but I want to leave it in the truck and make a parts chaser. Think black primer, lowered with wild color rims. I may have traded for a 84 GMC K20? that ran 2 years ago when parked. I sold my 86 F250 4x4 with a 460 and now need a truck to tow my 16' trailer.


Lynn

[Robyn]

Aero, Bummer :( That pretty well seals their fate then.

Jerry

The main bearing caps sit down into the block slightly.
On either end of the caps is a little ledge in the block, if a crack starts in that sharp cut and runs down the web its pretty much game over.

In most cases of main web cracks the crack will be within one of more of the center three mains outer bolt holes.

The cracks start on the inside of the hole within the threads and progress outward and then through the web, traveling upward (engine upright) and can in wost case scenarios actually penetrate into the cylinder walls and I have even seen cracks go into the cam bearing bore area.

In many cases the cracks are well within the depth of the bolt holes and some may only be visible with the aid of die check, magnaflux or what I use ***Heat the web area a bit with a propane torch after the block is washed clean*** Heating the area to just hot to the touch will cause any oil trapped in a crack to seep out and make a very noticeable line of black on the casting.


With cracks at the "Register" there is really no sound way to repair the thing.

If the crack/s are not too lengthly the block could be reused for a light duty vehicle but I would not do it.

Now
Cracks within the confines of the outer bolt hole are easily fixed using a
Lock and Stitch insert

This thread insert is not like a Heli coil or other coil type thread repair devices.

This repair unit is a a solid round steel piece that has a small flange on the end that faces the part line (where the block and cap meet) and the device has the proper internal threads to accomodate the main cap bolt.

The outer portion of the repair device has very unusual threads in that they are steeply angles towards the part line. (Sort of like the branches on a Christmas tree)

The harder the pull on the insert the more it tries to pull the crack back together.

The reason the blocks crack is due to internal stresses in the casting and possibly metalurgical issue too.

The bolt threads as the bolts are torqued create enormous stresses in the threads. The forces are similar to driving a wedge into a piece of fire wood.

Along with the internal stress in the block the added stress in the bolt holes results in the cracking.

The issues are many but AMG/GEP fixed the problem in the new blocks by changing the material makeup of the block as well as slight changes in the internal dimensions of the crankcase.

Now back to the insert.

The insert is made of a very tough steel material and thus handles the spreading action of the bolts real well with no tendency to crack.

The tightening force of the bolt pulls the area of the crack together and stops any further spreading or propagation of any cracks.

Testing of these inserts has shown this repair to be a lasting and reliable one.

I spoke to a local engine builder some months back and learned of the process.
They had been doing this to all their cracked 6.2/6.5 blocks for a long time and to date have had ZERO failures due to main web cracks.
(But did not offer the service as a repair on outside jobs)

This insert technology is in use for repairing many other items that have seen casting failure and short of a new casting have no easy repair.


I purchased the tooling to do the 12MM outer bolt holes last fall.
To date I have done several 6.2/6.5 blocks for local shops as well as my own stuff.
I will eventually purchase the tools to do the 10MM outer bolts (later engines)

The engine thats going back into DaHooooley has all 6 center main outer bolt holes inserted.

All 6 were done because now they wont fail. I only found one with a very small crack but with the engine block down, clean and being bored anyway it was a perfect time to do the repair.

The block has to be completely apart to do this machine work and then completely flushed and the cam bearings replaced (to be sure no metal gets in the oil holes to later cause trouble)


I would not use a GM cast 6.2/6.5 without inserting the 6 outer main bolts on the 3 center mains.

Also I would not use a block with the oil squirt holes in the main saddles

The early 97 blocks were the worst at cracking through the squirt holes.

There is no fix for this mess.

The only older blocks I would use (6.5 only, all 6.2's OK)

Casting # 599, 929 and possibly 141
IMHO anything with squirt holes in the mains should be avoided unless it is a new casting from AMG/GEP

The new stuff seems to be great.

Now you can find 6.2 engines built from about 90 to 94 that are built using the 599 casting and they also have the one piece rear main.

The exact date they started using the one piece rear main on the 6.2 I am unsure of but it was prior to the introduction of the 6.5

The Military got these blocks even after the 6.5 was in the civilian rigs.


Hope this helps clear up any ambiguity :)

Any other questions just ask and someone will chime in. :D


Robyn

[jerry598]

Thanks Robyn.

My 929 block is at the shop to get inserts in the 6 outer main holes now. Only one was cracked, not deep and not involving the register. Guess I'm still on the right track. Thanks again for all of your help.

Jerry

[Aerodyne]

I found a 97 block on Craigslist that looks crack free. Its a 506 with piston oilers. I also picked up a crank that will need to be turned. I don't care much for reground cranks.

Robyn I know you don't like the blocks with the squirts but could this block be useable. I didn't remember that till I reread your post.


Lynn

[Aerodyne]

For what it's worth I looked at the casting number on the block with the broken crank and it's a 599.

At this point I think a trip to the machine shop to have the 506 block checked out is in order.


Lynn

[Robyn]

If the squirt block has time on it and is not cracked it may be a fine piece.

Here is a tech tip from missy's garage.

Debur and chamfer (Lightly) all corners, all bolt holes, all oil holes ect.

A small electric drill with a counter sink is ideal.

Just touch all the lower end oil holes in the main saddles and break the sharp edges.

Not a lot but just get rid of the sharp edges.

These sharp places are stress risers and ideal spot for cracks to start.

Using a file break the sharp edges on the part line of all the center mains, both the block and the caps.

Get all the main bolt holes with your little counter sink too.
A chamfer width of 1/64" is plenty.

These engines are literally like a bag of razor blades in the lower end.
Very poor machine shop practice to leave all those sharp edges

Check the bottom of all the cylinder bores too. Looking up from the bottom, make sure that if there are any little nics in the cylinders lower edge that you smooth these out.

Now these nics that may be there are in line with the squirt holes and are a result of the tooling coming into contact with the cylinders lower edge.

These nicks can precipitate cracks forming and going up the cylinder walls.

Even the outer edge of the main bearing bores can be smoothed a little with a rolled up piece of emery cloth.

A round stone (Sharpening stone) can also be used to do these bores.

Any sharp edge needs to be broken to help eliminate stress risers.

All part of the way overused term "Blue Printing"

Make very sure that before you start stuffing parts back in that all the squirt nozzles are in the passages in the main line.

There is a nozzle for every cylinder. Leave one out and you will have a huge internal oil leak that will result in very poor to zero oil pressure at idle.

If the stock cam bearings are in good order they can be left in the block.
If the block is bored the cam bearings need to come out so the oil groove and passages behind the bearin gs can be cleaned well. (No exception)

Any shavings that fall into the oil holes of the cam bearings can become lodged there and not wash out readily and surface later to cause trouble.

Keep us posted

Robyn

[Aerodyne]

Thanks Robyn

It would still be a good idea to put inserts in the outer bolt holes on the three middle mains right?

Lynn

[Aerodyne]

I'm working on a Case Uniloader with a 4 cyl. diesel. Number 4 rod bearing went out so it needed a trip to the machine shop. If you are going to the machine shop why not have the 506 block checked for cracks.

The block came back crack free with cylinders honed and new cam bearings. Must have been a breakdown in communications. The cylinders were good to go without boring.


$187 later I have a block ready to build but no crankshaft. I hope the 141 block is still at pullapart.


Lynn

[jerry598]

Thanks Robyn

It would still be a good idea to put inserts in the outer bolt holes on the three middle mains right?

Lynn

Robyn must have missed this one unless she replied in a PM. She told me just that - do all six outer holes, which I did. The shop charged me $40 each. Do to other delays, the engine's still not in the truck yet.

[Aerodyne]

Jerry

Thank you


Lynn