69 L36 Head Gasket Part # Question

[Floyd B.]

I have a '74 Corvette Parts and Illustration Catalog and the head gasket information seems to be ambiguous for 427 H.D. applications.

Group 0.289 Gasket Unit - Gasket, Cylinder Head

one entry has:
68-69 Corvette w/H.D. (427) 3974218

Another entry has:
68-69 Corvette w/H.D. (427) 3969865

I see several NOS head gasket sets listed on ebay that claim to be correct for all Chevy 427/454 applications 69 - 76. This part appears in my part book as:

73-74 Corvette (454) 330860

I assume all these gaskets COULD be interchangeable since the 427 and 454 both have 4.25" bores

Can someone please tell me which of these gaskets will be functionally correct for my L36? Is there any visually detectable difference when the engine is assemble (i.e. will it make any difference when the car is judged?)

Thanx

[Duke W.]

Re: 69 L36 Head Gasket Part # Question

It's easy to determine if an engine has an original or equivalent head gasket by measuring its thickness with feeler gages at any corner of the head-block interface, but it's not part of the judging process. The OE gasket for your engine was a steel shim type, and I think the thickness was .028".

Iron block aluminum head combinations need a composition gasket to prevent fretting due to the difference thermal expansion rates of cast iron and alumium, and typical composition gaskets are in the .035-.045" range. All other things the same a .010" increase in gasket thickness with reduce CR about 0.3.

I'm sure Joe L. will be along with more specifics.

Duke

[Joe L.]

Re: 69 L36 Head Gasket Part # Question

I have a '74 Corvette Parts and Illustration Catalog and the head gasket information seems to be ambiguous for 427 H.D. applications.

Group 0.289 Gasket Unit - Gasket, Cylinder Head

one entry has:
68-69 Corvette w/H.D. (427) 3974218

Another entry has:
68-69 Corvette w/H.D. (427) 3969865

I see several NOS head gasket sets listed on ebay that claim to be correct for all Chevy 427/454 applications 69 - 76. This part appears in my part book as:

73-74 Corvette (454) 330860

I assume all these gaskets COULD be interchangeable since the 427 and 454 both have 4.25" bores

Can someone please tell me which of these gaskets will be functionally correct for my L36? Is there any visually detectable difference when the engine is assemble (i.e. will it make any difference when the car is judged?)

Thanx

Floyd------


The gaskets for HD big blocks (i.e. L-88 and ZL-1) were composition-type gaskets. These were all discontinued many years ago but sometimes show up on eBay for big $$$$$.
l
All other 65-74 Corvette big blocks except L-89 and LS-6 used steel shim type gaskets. My recollection (I'm out-of-town right now so I can't confirm with my references) is that the GM #330860 was the last steel shim gasket from the 1973-74 period which also SERVICED all non aluminum head 1966+ Corvette big blocks. The 330860 is GM-discontinued but an equivalent is available from Victor-Reinz and others.

[Wayne M.]

Re: 69 L36 Head Gasket Part # Question

I've got two "gasket units" which include the head gaskets as well as a bunch of other stuff.

The 3863199 steel gasket shows in my Jan '70 P&A catalog as for 66-70 427-454 (exc. H.D.)