High Mile overhaul

[Robyn]

I recently lost the 6.5 in one of our Subs and have posted a few other items asking some ??? such as about the DS4 to DB2 swap.

Well I found the issue that brought this old girl down.
255K miles (original) and the truck has always had Amzoil in it since new.
I got the top off tonight and the #2 head gasket had blown forward past the fire ring into the front water passage.
The gasket was totally wasted and the fire ring was all ate up and finally burned through. The block is etched out some just outside the fire ring area so I am going to have the block decked to be sure.
The Cylinders still have cross hatch hone marks in them and NO wear at all that can be easliy measured with an inside micrometer.
The plan is to finish the tear down over thios weekend and get the block tanked and magnufluxed. If it mags OK its off to get decked and then soft plugs, cam bearings and a quicky hone with a bottle brush hone.
I am going to put in a new set of pistons just because and a set of new heads from Clearwater cylinder head.
I looked at a couple lifters and they look new. I will pass judgement on the cam after I see all of it.
Also the #7 cylinder was about to lose the gasket out the back just as the other one went. The block is not eroded but a decking will be sweet.
All in all I am very pleased with what I found.
I have all new wiring harnesses for the DS4 and the main harness for the engine that goes under the manifold and feeds all the sensors, pump and such.
I am also going to replace the filter harness too as it is toast and the plugs are in sad shape from time and heat.
I really had not intended to use Amzoil this time around as it is tough to find when you are traveling, but such long life with little wear is very convincing.
I am very anxious to see what's in the bottom end of this little beast.
Momma is hot to have her Burban back so I'm a gonna have to hustle.
Will add more as I find out.
Robyn

[john8662]

Look at the top of the cylinder bores, with the block sitting upright.

There will be a ring groove worn in the cylinder bore usually starting at the top of the bore but will not usually travel all the way around the top of the bore.

Take your fingernail and see if you can catch the ring groove in the cylinder bore. Just something to look for before deciding to bore the engine or not.

Most engines will need to be bored, especially at that mileage, but it's good that the wear was low! To verify bore, measure one of your pistons and see what bore clearance you have, the pistons don't wear much, or not as much as the cylinders do.

The cam is likely to be in good shape, they hardly wear, just have the machine shop inspect it, or lightly polish the journals as you'll be doing the crankshaft.

Replace the lifters, even if the "look" good, but it's up to you.

Not a bad idea to replace the pistons either way, after seeing some that have cracked over time.

[Robyn]

This is a very unusual case as there is no sign of the usual "ridge" at the top of the cylinder. The bloody thing is like it was new yesterday. The honing marks are quite prevalent all the way around from top to bottom.
I have never seen this in an Auto block even at much lower miles.
I am sure this thing has not been replaced as there are none of the tell tale signs that the engine has been out. all the hose clamps were the original squeeze type and all the hoses are original as well. The little brackets that are a bitch to get to and almost impossible to unbolt were still all intact and neat. The overall picture of the outdside of the engine was "Filthy" with 12 years of crud on it.
The original owner confirmed that the DS4 had been off while he had owned the truck.
The one thing I found strange though is that there was no marking on the push rods as described in the GM service manual noting which end is top.
I found most of the push rods had a small "punch" mark, but the marks were sometimes on top and some times on the bottom.
I think I will replace them as well as the lifters just to be sure.
Any input here would be helpful. I have built a load of Chevies over the decades and never seen such nonsense. The big blocks in some years had a hardened area that ran in the guide plate but it was obvious where it went.
This is a 599 Block I noticed.

[john8662]

very odd indeed.

Sometimes the paint on the pushrods wears off or is covered with oil and not visable. Thats why you've got to take a paint pen or some other marking device and mark them, then you can re-install them in the same orientation.

I noticed the notce on one end or the other too, no rhyme or reason to it, even though they had the mark on them.

I don't know how to tell otherwise, not that is a HUGE deal or anything...

Just check for crack in the main webbing when you get it that far, then you've got a golden engine to rebuild.

What are you specs while mic'ing the bores?

J

[Robyn]

Well the sucker is all torn down now.
Boxes of parts everywhere.
The bearings looked very nice for over 200K miles, some etching and a little flaking of the outer layer of bearing material but if the head gasket had not gone away they would have carried this engine a looooooooong time further down the highway.
The bores are within a thousandth overall.\I am just going to bottle brush hone them and deck the block. Will use the pistons cut for the decked block.
New heads a lick and a promise, ooops dont forget a couple rattle cans of fast black engine paint to make it look nice.
I tossed all the lifters in a can, the cam is sweet and I will install new lifters as it is just a great idea with this many miles. My luck one would collapes and there I would be tearing it apart. NO THANKS
I was beginning to think that maybe this engine had been gone through or replaced untill I got to the bearings, marked 10-93 so its original.
Funny there were no numbers on the rods and caps so I numbered them as I took them apart just as one would expect to find a GM V8. Number out
LH 1-3-5-7 RH 2-4-6-8
Timing chain is a tad loose so its gonna get a new one too

[16gaSxS]

Robyn, Have you given any consideration to lowering the compression on the engine? How about having the piston tops and heads ceramic coated?
Good luck, it's a shame the gasket issue happened on this engine.:(

[Robyn]

I took the block and crank to the machine shop yesterday to be tanked and magged.
After looking things over some more the plan is to reuse the pistons and just do a ring and bearing job as well as replacing the heads.
I spent yesterday afternoon late washing up and organizing all the bolts, nuts and various small parts into marked sandwitch bags and boxing them for quick retrieval when the block and crank get back.
Nothing I hate more than sorting through cans of bolts when I am ready to assemble.
200K+ definately leaves things real mungy.
I had to order the .010" thicker head gaskets from LA as the local suppliers did not have them in stock. Bearings and stuff as no problem. I still as yet need to Mic the crank and see what the bearing sizes are. I do hope this sucker does not have a batch of select fit bearings of all different sizes..
Well all for now, will post more when I know more.
Robyn

[john8662]

Every 6.2/6.5 that I've taken apart has had the select fit bearings.

You can tell by looking at the bearings. Stamped on the back will be one of three things.

Just a part number = STD
.013 us (it's metric) = .0005"
.026 us (again, metric) = .001"

When taking one apart I take note of where they're at.

Usually a person gets away with just putting all STD bearings in and going on.

I'll bet you're going to plastigage the journals to see what your clearance is. If you're slightly low, that's what the slightly oversized bearings are for. You can get the .026mm from Federal Mogul and Clevite and GM, you can only get the .013mm from GM.

From my readings on Clevite catalogs, etc. you normally put the larger bearing on the cap side.

The 6.2 I put together actually required STD on the mains (some were close enough to almost put the .001" in) and the rod journals ALL needed the .001" bigger bearings installed to get the clearance right, was a little low on the rods journal on the crank.

J

[Robyn]

Well I saved all the bearings and know where the individual inserts came from so we are good to go. I think they are std but will need to look to tell for sure.
Thanks
Robyn

[Robyn]

Well
Good news, the block and crank are back from the shop with a clean bill of health. The Block got a tanking and new soft plugs.
The cylinders honed lightly on the power hone and a general looking over as well as a mag job to find any dreaded cracks.
The crank is clean and pollished and all good to go too.
This is wonderful news as I am in need to get this rig back on the road.
I have almost all the new parts in hand now except one wiring harness that will be here by weeks end.

Will post more as it goes back together.
Robyn

[jspringator]

What about studs for the heads instead of the TTY bolts?

[Robyn]

Not sure but it might be worth looking into!!! GOOD Point

[Robyn]

Well good news
Starting to put the beast back together.
Got the cam in and checked all the main bearing clearances and finished bolting the bottom end together this afternoon.
I would have liked to have had the .013mm under mains but I am not going to spring for Gm's usery on them. I used standard Cleavite77 STD and the clearance is .0028 - .003 inches
Not the least they recommend but within spec. Thats what they make STP for "dont ya know" HAAAAAAAAAAA
Spec is from .0017-.0032 Inches.
I am of the mind set that .0017 is just to bloody tight. .0025 would have been sweet but not worth almost 3 times the cost of cleavite bearings to get it. The rods will be fine as they were STD coming out.
All for now
Robyn

[tommac95]

hope ya spring fer a new harmonic balancer/vibe-dampener!

The lack of wear is impressive--mine at 175K seemed to have about .002" wear on 6 cyls, and .007" wear on the other two.

Too bad all the 6.5s don't go like that.

[farmerherb]

Robyn, thats why use Amsoil. I have 340,500 miles on engine and trans. Everything original except injectors, alternator and water pump. Always used synthetic oil.