1. Best guess on your cylinder heads is that they're the Corvette heads that got developed into the "ZZ" style, as would be installed on the "ZZZ" through "ZZ4" crate engines. They're fine entry-level cylinder heads.
2. It's not the rocker studs that are the problem, it's the extra-tall rocker nuts. Get shorter nuts and use the centerbolt covers, or
3. They're aluminum, it'll drill easy--IF (big IF) there's enough metal around the hole to go oversize. "I" would install Heli-Coils in those holes and never have to worry about stripping them out again--but that assumes there's enough metal to do that. I'm thinking that since the castings were not intended to have holes there...things are not going to be easy.
4. If at all possible DO NOT USE RTV SILICONE. A real valve cover gasket, stuck to the valve cover with actual gasket sealer would be preferable.
5. Those valve-cover bolt "load spreaders" work, but there are better ones. The good ones are much longer, and have formed ends so they're "springy". GM discontinued them in favor of long ones with plain ends, which are still better than what you have.
The aftermarket still sells the springy ones. These, and a hundred other Chinese knock-offs.
www.summitracing.com/parts/mil-85305
6. I can't tell from the photo if your pushrods are merely polished from contact with the guideplates, or if they're being destroyed by the guideplates. When using pushrod guideplates, the pushrods MUST be hardened--and not many stock Chevy pushrods are hardened, 'cause they're not used with steel guideplates. Lotsa aftermarket pushrods are hardened, though.
2. It's not the rocker studs that are the problem, it's the extra-tall rocker nuts. Get shorter nuts and use the centerbolt covers, or
3. They're aluminum, it'll drill easy--IF (big IF) there's enough metal around the hole to go oversize. "I" would install Heli-Coils in those holes and never have to worry about stripping them out again--but that assumes there's enough metal to do that. I'm thinking that since the castings were not intended to have holes there...things are not going to be easy.
4. If at all possible DO NOT USE RTV SILICONE. A real valve cover gasket, stuck to the valve cover with actual gasket sealer would be preferable.
5. Those valve-cover bolt "load spreaders" work, but there are better ones. The good ones are much longer, and have formed ends so they're "springy". GM discontinued them in favor of long ones with plain ends, which are still better than what you have.
The aftermarket still sells the springy ones. These, and a hundred other Chinese knock-offs.
www.summitracing.com/parts/mil-85305
Milodon 85305 Milodon Valve Cover Hold-Down Tabs | Summit Racing
Free Shipping - Milodon Valve Cover Hold-Down Tabs with qualifying orders of $109. Shop Valve Cover Hold-Down Tabs at Summit Racing.
www.summitracing.com
6. I can't tell from the photo if your pushrods are merely polished from contact with the guideplates, or if they're being destroyed by the guideplates. When using pushrod guideplates, the pushrods MUST be hardened--and not many stock Chevy pushrods are hardened, 'cause they're not used with steel guideplates. Lotsa aftermarket pushrods are hardened, though.
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