Diesel World – October 2019

Q&A

to check if you have a gasket/injector leak? I guess it

would not have made any difference to me. I had to

tear it down to the heads anyway. If someone (like

me) replaces the water pump and still has a hard

upper radiator hose, they may wish to check to see

if exhaust gases are penetrating into the coolant.

What I really want to know is: if, theoretically, you

had your engine stripped down to the short block

and you wanted another 300-500k miles out of it,

what modi cations would you do? I already have

ARP head studs. Would you do anything with exhaust

gaskets, crossover pipes, exhaust manifolds, etc.?

Thanks for all your help,

Joe Kowalski

Edmonton, Alberta

Back in the 1990s I had a 6.2L diesel that had

a bad head gasket. We all agreed on it—there

was no doubt, but we thought to do a CO test

of the radiator gases to con rm anyway. The

test turned out to be inconclusive. Since that

time, I've not put a great deal of trust in using

a CO (carbon monoxide) test to positively

identify a leaking head gasket that causes

cooling system overpressure.

The Duramax head gaskets have gone

through multiple generations in improve-

ments. Just as 6.2/6.5 head gaskets are better

today than the originals, I suspect the latest

GM head gaskets for the Duramax are better

than what these engines were equipped with.

Because GM pays for in-warranty repairs, I

suspect they have a bigger stake in ensuring

that the gaskets they use are the best there

are to ensure a long life. Several aftermarket

gaskets are available for the Duramax. I'll

stick with what GM recommends.

I am a fan of the OE Torque-to-Yield head bolts

for non-modi ed, factory-performance diesel

engines. The elasticity of the bolts help them

to maintain clamping force over the life of the

engine. But, if I were building a performance

engine, I'd likely install ARP studs because

performance engines usually produce a shorter

cycle life than stock engines found in a daily

driver. A careful preparation of all components

(head and block decks), resealing the injector

cups (for an LB7), and a careful reassembly

should provide a long and useful life for a

Duramax driven by the average person (hun-

dreds of thousands of miles). From a longevity

standpoint, nothing much else needs to be

changed. Careful assembly, clean assemblies,

and attention to detail are important.

Industrial Injection recently began offering an

aftermarket injector cup for the LB7 Duramax

that screws into the cylinder head, thus making

it more reliable and leak-free. It would be hard

not to recommend this addition when complet-

ing a repair that you want to last for a long time.

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http://www.dieselworldmag.com OCTOBER I 2019 • DIESEL WORLD 141