Planning to use a set of steel shim gaskets on my '70 455. I've been watching videos on gasket prep, and while it sounds like the newer more modern gaskets don't require any type of spray, should I be considering a copper spray (or something similar) for a steel shim gasket?

 

Copper spray is what I use

 

Cometic says no spray but I used copper anyway with no problems. NOS, for sure use copper...

 

 

Cometic has a coating on their gaskets that is supposed to flow when heated up to help seal minor imperfections. Copper Coat might not let it work like it should. I know you have done it with no issues but someone else might not be so lucky.

As far as the original question I prefer HiTack spray instead of Copper Coat but I have probably used less than 5 sets of shim gaskets in the last 40 years.

 

I would not have likely used anything but in a video that Bill Trovato made, he said he uses silicone on them if I remember correct. He said the same thing that cometic don't recommend it but he does it anyway. I figure he knows more than me. That said, I didn't want to use silicone. I would need to see the video again but I feel sure he used regular clear silicone.

 

A good coating of aerosol aluminum paint always worked for me.

 

High heat paints are generally silicone based so I can that working..

 

I'll try the copper spray on the steel shims and give it a roll...

 

If surfaces are clean and true there will not be an issue with or without spray.

 

I have used 6 or 7 sets of the Cometic MLS gaskets on Olds and Pontiac engines without adding any spray and I've had no sealing issues at all. I think that clean straight surfaces are important though.

 

I used copper spray on the FelPeo gaskets I installed recently.

 

Hi tack all the way.

 

A huge variety of opinions here!
Last steel shims I used with copper gasket coating. A Pontiac 400 with no new surfaces machined and it was fine. Next set is NOS Olds and this yr, will use the same again.