I have not been here in maybe 4 to 5 years, Please help me out.
I have the car as shown in my signature. The factory steel stamped covers leaks as well as Summit chrome steel stamp covers. I am using the 1/4" thick rubber gaskets.

A mechanic is suggesting that maybe aluminum cast valve covers would not leak, Does anyone have a suggestion for me. These are center bolt valve covers.

 

The valve cover are apparently leaking off of the rear of the valve covers.

 

I imagine the extra rigidity which I assume cast covers would have would help, but I don't see why steel stamped covers wouldn't work in the first place. Where is it leaking from? If you have the covers off, do they sit flush on on flat surface?

EDIT: Looks like you beat me to the first question.

 

I have cast aluminum covers and mine leaked in the back to, only way I could get them to stop was to glue two factory rubber gaskets together then smear a thin bead of gasket maker on the head then install the valve cover. Are you putting any silicone on the gasket before putting it back on? if not maybe try that.

 

I have a mechanic looking at my car. The engine is leaking in back somewhere, I assume from the valve covers. The starter motor is covered very badly.

The AFR heads are not machined as they should be. This is hard to explain in words. Of the four rounded corners of these heads that interface with the valve covers, the two on top have not been machine with a definite rail. The bottom two are machine like Chevy does it. Also, the push rod guide plates leave very little room for the inner lip on the valve covers to fit down snug.

I was hoping that cast aluminum valve covers would fit better. But they might have the same problem.