New heads

[westcoasttowing]

I just purchased new heads. I torqued them down exactly as specified. Finished final assembly and began to add coolant. I then noticed coolant pouring out between the pass. side head and the block. Tore it back down and noticed my block was now cracked in the cylinder wall of the cylinder all the way in the back. I then noticed that on my new head's surface that mates to the block, the injector pods are actually raised about about a 1/200's of an inch. I called the manufacturer and he said that is the way they are. My old heads are smooth. Is this normal. I'm thinking this could of caused the cracked block. It was not cracked before. Any thoughts?

[DmaxMaverick]

Welcome aboard!

The injector Pre-cup (pod) isn't protruded too much at .005". Most are much more, still within spec. Less than flush is not acceptable, and about the only time they will be flush is if the head is milled with them in installed (not recommended, in most cases).

Your crack was either already there, or well on the way. The head bolt torque process may have finished it.

[westcoasttowing]

so then its okay to install them on another block? So does the gasket then absorb the protrusion? Thanks so much for your help.

[DmaxMaverick]

Yes, the gasket takes up the protrusion. Have a look at the old heads and gaskets, if you can.

I don't know that they are OK for using again (without actually inspecting them), but they should be if they were good to begin with. There are just too many factors to consider. For one, reusing old head bolts can cause issues in itself, such as over-torquing and damage to new gaskets, or thread-pulling. TTY bolts can be counter-intuitive to some old school builders, who may not understand the associated concept and design. If you are going to reuse the heads, I recommend having them inspected and tested by a reputable machine shop.

[westcoasttowing]

my old heads had multiple cracks. I did use new bolts. I ended up getting a good used block. I'm going to chase the threads on the block, use new bolts and pray for the best. Wish I could find a good deal on a cummins. This motor has got me down.

[More Power]

I've seen new AM General heads... The precups are all exactly flat with the head decks.

If by "new" you mean reman'ed, that could explain it. Or, if by "new" you mean "imported", that could explain it.

[john8662]

The precups are supposed to protude .001" - .002". It's not much and to the naked eye you won't see it, but you can feel it with your fingernail, as it will catch.

The easiest way to measure this is with a Bridge fixture and a dial gauge that was zero'ed on a flat part of the deck of the head.

AM General heads meet all the specifications of the new heads. I've had several sets of new AM General heads disassembled and checked completely before assembly on an engine just in case. They always came in perfectly to specification, including the small amount of precup protrusion.

Bummer on the block being cracked, this is not common. If in doubt about the precups, take the heads to a machine shop and ask them to measure them, it'll only take a minute.

[westcoasttowing]

yes the heads i have are new heads made in the US. the 2 pods towards the front measure .005 the back 2 protrude slightly more. Why would they ever protrude at all. What is the purpose? I looked in to have them milled. More than one machine shop said they cant mill them down. That the steel used for the pods are way too hard.

[phantom309]

don't let the old 6.5 get you down,.

Cummins is not always the answer either,.
i just got thru helping a neighbour with his 12V ,.they can be real expensive pita's too,.
He has an old 24V as well, and it just will not start,. we,re into trying to borrow an ecm for the damn thing,..
and he is some jealous right now of my old leaky rattly old v8 detroit,.

I prefer to use head studs rather than bolts,. they will hold the lids on much better,.especially if it gets a little more boost than stock,.;) lol

[westcoasttowing]

is there a better head gasket i should use in this situation than the felpros i used last time?

[phantom309]

is there a better head gasket i should use in this situation than the felpros i used last time?

I am down to my last pair of military ones,. they seem to be a lot more substantial,.not easy to track down tho,.

as for your precups ,. they;ll settle in ok when you tighten things down,.

[Robyn]

Felpro gaskets are are best in the business for these engines.

A few other companies offer gaskets, but felpro is the real deal.

[john8662]

yes the heads i have are new heads made in the US. the 2 pods towards the front measure .005 the back 2 protrude slightly more. Why would they ever protrude at all. What is the purpose? I looked in to have them milled. More than one machine shop said they cant mill them down. That the steel used for the pods are way too hard.

The Precups are Stainless Steel, that's why the machine shops didn't want to mill them.

Might take a rubber mallet and ensure they're fully seated in the head, then measure again.

The next step for repair would be to remove the precups and machine the pockets in the heads a little deeper to get the right protrusion.

They are engineered to protrude to ensure that the clamping force of the cylinder head gaskets keeps the precup from moving, which would degrade the seal for the gasket.

Send the heads back for repair if they're not right.

John