It's been so long since I've had anything original, I don't recall how GM sealed the valve cover centre bolts.
Was it copper only? Or copper with a rubber washer?
In my case, this latest rebuild now has a slight leak at one the bolts. I've used various combinations of different types of washers in the past but I'd like to get back to square one.
FTR, these are aftermarket cast aluminum covers (Proform) and I didn't use their hardware as they weren't the correct length for the RHS heads. They had a steel and rubber mix with a flanged bolt.
Seems to me that the Vortecs I had and Chevy stamped steel covers were copper only.
Anyone have an original specimen and can confirm this?

 

These are what came with the Proform valve covers. Unusable with my heads though (actually snapped two of them as they bottomed out and I was unaware this would happen.)



It's a flanged bolt with with a flat steel washer which is supplemented by a rubber gasket.

Rock Auto yielded a GM PN 10066008 that was spec'/d for a 97 Chevy pickup with the Vortec 5.7.





Also a flanged bolt head with a steel washer. There is no rubber washer however.

I've got a set or originals that I scooped from the junkyard when I got my over the counter Vortecs. They're similar to the Rock Auto bolt although they have a copper washer. No rubber.
So is it a best guess that the General used both copper and steel as original equipment with no rubber?

I can't say for certain why I've got a leak now whereas before the rebuild, the engine was tight. This is why I'm revisiting this bolt/washer thing and get back to being drip free.
Presently, I'm using copper washers that I machined (gotta love EDM!) which fit snugly on the bolt shank. I've also added a rubber washer beneath that however the rubber tends to squeeze out which may be the source of the leak.
For those with a centre bolt setup I'm asking what the bolt is comprised of.

 

What about using something like this?
EPDM Neoprene Rubber Bonded Sealing Washers
They come in stainless also.

 

Depends on the year and motor type. Below are all the different options of what was used on the stock valve covers.

88 - 92 (L03): 12338092 bolt only
87 (L98): 12338092 bolt & 14094717 washer
88-92 (L98 & LB9): 10088165 bolt only


I too would suggest what @NoEmissions84TA posted as your aluminum valve covers came with the gasketed material. EPDM material should hold up well.

 

Interestingly, I saw those on another brands bolt offering. They didn't appear to be available separately though.
I'd say that would be the way to go. The bonded part of the rubber to steel is the ticket here. They remind me of the washers used in assembled steel buildings. They'd be underneath every teck screw used.
Thanks for that Mr. No. I'll look into those for sure. I just have to find the appropriate size. Which would be 1/2" O.D with a .250" I.D.
I'm literally minutes away from this seasons first start but I've got little details such as this to address first.



Just woke up from a long winter's nap. Needs a bath and fully charged battery.

 

Nothing like part numbers to work with! Thanks for that.
I'll agree that No's suggestion is the way to go.
Home Depot carries a size close enough that could, I think, easily be modified to work. 1/2" O.D. although only a .125" hole. Corrected with a drill bit and some finesse.
$3.97 for ten!
Thank you all.

 

We need the under the hood pic.

I did some searching for you: (304 SS)
100-Pack Bonded Sealing Rubber Washers, #12x1/2" OD Neoprene Washer Gasket | eBay

 

You've certainly put me on the trail to getting something that should do the job.
I went online locally and found these about 15 minutes from where I work!



I just have to determine if 5/8" O.D. will fit in the bolt pocket in the valve cover.
As for an under hood picture, I'll see what I can do.