Engine/Transmission (1994 - 1998) 12v Head Gasket Bolts

[WOTURBO]

I'm Replaceing The Head Gasket On My 12v, Should I Replace All Of The Head Bolts? What Thickness Of Gasket To Go With... . Stock Deck Height?

 

[PRattenbury]

Kinda depends on why your previous one failed, and what your intentions for the future of the truck are. If you're stock and plan on staying that way, just put a stock thickness gasket in and put it back together. If you plan on a little more boost due to a bigger turbo or whatever and don't intend on using water/death, put a Cometic MLS gasket in there. If you have the extra coin, a set of 12mm studs would be more insurance. If you're going to add water/death or plan on in excess of 50 psi boost, or both, then studs and o-rings become a must. Just depends on you, and your pocketbook.

 

[WOTURBO]

I Was Leaking Coolant Under The T-stat Housing... I Was Changeing The Oil And After It Was All Drained I Looked In The Drain Pan And See Nice Green Coolant Sitting On Top The Oil... . Any Ideas?

 

[Shadrach]

Under normal conditions the head bolts don't need to be changed. Shadrach

 

[Vaughn MacKenzie]

New ones aren't very expensive, I was told to get new head bolts & never reuse the old ones.

 

[Bob V]

New ones aren't very expensive, I was told to get new head bolts & never reuse the old ones.

I thought they where $20. 00+ each

 

[Vaughn MacKenzie]

No no, as I recall an entire set was ~$85 from Cummins NW but that was a couple years ago.

 

[hsmith]

Not a lot of money for new bolts from Cummins and good insurance. Be sure to clean the holes real good.

 

[Joseph Donnelly]

Generally the head bolts are reusable, even if you have added power and boost pressure. Mop out all the holes with Q-tips and oil the threads and shoulders of the bolts. They should come up to 115-120 ft-lb smoothly and quickly if they are still good. In my experience if any are marginal, they will be the medium length bolts, not the short ones near the exhaust manifold or the long ones at the rocker stands. The Cummins gasket originally used in marine applications is now the standard replacement, 3283335. If you have added a lot of boost/power, you might want to reduce cylinder pressures and static compression with the . 010” thicker 3283337 or . 020” thicker 3283339 gasket. The last will reduce compression from 127. 5:1 down to 16. 4:1. While the head is off, it would be worthwhile to get a valve job done and go to the 60 psi valve springs if you will be using an exhaust brake or a governor spring kit that allows more rpm (in the latter case, change all 12 springs). Definitely check the deck for warpage after thoroughly scraping it and wiping it with solvent on a clean rag. Have the head surface checked. It may be warped about . 008” and have erosion at the gasket sealing bead areas for the cylinders. If so, get it resurfaced by a shop that understands diesels and will put a very smooth finish on it, about 60 microinches. You won't be able to catch a fingernail at all in the tool marks (“scratches”).

 

[Shadrach]

If you want to change the head bolts you will need 6 short p/n 3920779, 14 med p/n 3920780 and 6 long p/n 3920781. Price them out and then decide. Shadrach