Deep in over my heads!

[Subzilla]

Finally took the plunge to install that ATS turbo system that's been sitting on the garage floor for a year and a half. It's going on Subzilla. Last week I tore apart the engine down to the head gaskets at the advice of TDP fellow members to replace these old and tired gaskets. The Sub has 305k miles and I bought it with 130k miles. I always assume it was the original engine with no internal work.

As Gomer said it, surprise, surprise, surprise! The gaskets are stamped Fel-pro and have the orange outline around all the holes. One of the previous 2 owners in the first 130k miles must have overworked it in its pre-pyrometer days, I assume. I was looking for a stamp on the pre-cups but the head and pre-cups are smooth as silk. No markings, no slightly protuding. Would this mean the heads have been machined down?

My plan was to have them re-worked so will this prior machining affect another head rebuilding? Would I need thicker head gaskets?

Also, the heads have the extra pre-'88 coolant passage as described in TDP R&R guide. Jim says to buy the 6.2 gaskets if they have this passage and not the 6.5 gaskets. BUT, the block does NOT have a mating passage in the same place. Is it suppose to?

One other observation: there is a thick carbon-like build-up literally running out of a few of the intake valves. Is this normal? It seems each piston/valves seem to look different from the others - more carbon on some, more roughness, more stuff running out of the intake valves, some looking cleaner........

This is new territory to me. Sorry for the many questions.

[john8662]

As Gomer said it, surprise, surprise, surprise! The gaskets are stamped Fel-pro and have the orange outline around all the holes. One of the previous 2 owners in the first 130k miles must have overworked it in its pre-pyrometer days, I assume. I was looking for a stamp on the pre-cups but the head and pre-cups are smooth as silk. No markings, no slightly protuding. Would this mean the heads have been machined down?

That's factory equipment, there isn't a GM Gasket, GM tasked Fel-pro for the OEM gasket. What you decribed is the original equipment felpro (their very best gasket, superior to the stuff on the shelf today).

The precups vary, most feel as though they're flat, and I'm sure they settle slightly over time. The spec is only .001"-.002" protrusion, very very very little, hard to feel. you need an appropriate dial gage to tell for sure.




My plan was to have them re-worked so will this prior machining affect another head rebuilding? Would I need thicker head gaskets?

You can have them rebuilt. I'd advise sending them to someone that knows these heads. These heads are hard to have rebuilt correctly. I have a few recommended places to send stuff like this. I would not allow your local shop to rebuild these heads. Chances are though, you'll be looking at different cores (luck of the draw in regard to cracks).



Also, the heads have the extra pre-'88 coolant passage as described in TDP R&R guide. Jim says to buy the 6.2 gaskets if they have this passage and not the 6.5 gaskets. BUT, the block does NOT have a mating passage in the same place. Is it suppose to?

There wasn't ever a mating port in the block for this funny shaped port. It's there as a means to clean out sand during the casting process. It basically needs to be sealed by the gasket because it's in the head's water passage. The issue that is caused by that port is when using a later 6.5TD gasket with a metal reinforcement plate. The plate doesn't allow the gasket to seal this area. The 6.2 gaskets don't have the plate.

I like a specific gasket for these engines though, I prefer the Victor Reinz gasket for the 6.2. It looks and functions like the OEM gasket (black/grey in appearance with orange outlines). Very good rigid gasket.



One other observation: there is a thick carbon-like build-up literally running out of a few of the intake valves. Is this normal? It seems each piston/valves seem to look different from the others - more carbon on some, more roughness, more stuff running out of the intake valves, some looking cleaner.......

Oil, most likely from eating years of blow-by gasses and some of the oil from valve stem seals. You could at the very least have new stem seals placed on these heads.

John

[john8662]

Just caught the part about the precups having no markings, yeah, probably been decked then, they should have some dots on them.

You can tell for sure, knock one of them out (using a faily blunt punch) angle your punch through the injector hole (injector removed naturally) and angle the punch to where the end your're hitting is angled away from the head. Basically there is a flat spot inside you can tap on, feel with the punch as to not have it fall in the opening of the cup.

Once you get one removed carefully you can measure with a caliper (digital or analog), measure from top of cup to the base, it will measure .865 or .8645 if they're stock. subtract from that if you suspect decking with the cups installed (wrong way).

J

[Subzilla]

Thanks for the replies, John! That makes sense.

What makes rebuilding these heads any different from any other heads? And how do I know if a rebuilder "knows these heads" other than relying on reputation/word of mouth?