[b-man]

Originally Posted by PontiacHO

Shoulda coulda woulda. I may send these valve covers back. As much as I like the look, I’m not going to modify them especially just to bolt down. Seems like the finned aluminum covers with center holes are $500. That’s beyond my budget.
How are the aftermarket chrome replica valve covers like what came on a 400? Thin?

The aftermarket reproduction chrome 1967 and later covers aren’t thin and flimsy, they’re comparable to stock originals. At least with new covers you’re starting with nice flat gasket surfaces without sunken bolt hole areas hat need to be straightened.

Myself I have some decent original chrome 1964 GTO covers on my 421 with double 1/8” rubber gaskets using Gasgacinch between them. I glued them to the covers with Permatex Hi Tack and smeared a thin layer of grease on the side the seals to the head. The reason for the double gaskets was to clear the polylocks on my Crower 1.5 rockers.

No leaks so far, perhaps the additional compressabilty of the stacked rubber gaskets helps seal the covers without distorting them with excessive tightening who knows.

Now you know why GM went to all cast aluminum valve covers, oil pans and valley covers and captured o-ring type gaskets on their LS series engines. They don’t leak.

I took these pictures while I was replacing the driver’s side valve cover, I wanted to install the California Emissions PCV breather tube so I needed to swap to a cover with a breather hole. My builder had used Gasgacinch to adhere the double gaskets to the blanked-off cover so they easily peeled off for reuse. With only about a thousand miles on them there wasn’t any reason to toss them, I kept them in the same orientation and so far so good.