Old 302 head job

[Jakem]

I have pulled my heads and installed new gaskets and seals. Nothing else changed. Now after install it won't stay running and doesn't sound good...any suggestions

 

[Bondo]

I have pulled my heads and installed new gaskets and seals. Nothing else changed. Now after install it won't stay running and doesn't sound good...any suggestions

Ayuh,..... One thread, in one forum, per problem,.......