[65 Lamnas]

Originally Posted by Jay S

If you didn’t know, Scorpion makes the rockers arms for both Isky and Howard’s. Isky bodies are the endurance versions, Howard’s uses the race version. I think even Summit brand rockers are Scorpions. There are a lot of those rocker arms out there working fine. Some are being used in very big cams also.

I mentioned the alloy they use being different than most rockers in the earlier post, I doubt the weakness is from the alloy, it is more likely to do with the machining tolerance that alloy has for assembly. Most cheap rocker arms (like a Proform) are made of a easy to machine 6061 alloy. Then the better rocker arms, like Crower’s Aluminum rockers, Harlan Sharp or the older Cranes were made of a 2024 alloy that is almost twice as strong as the 6061, but still easy to machine and forgiving to assemble. Scorpion opted to use a 7000 series alloy, I don’t know which 7000 it is, but it is likely slightly stronger and lighter than 2024. The down side though is it is harder to machine and the tolerance for assembly is tighter. The body using that alloy can’t flex as much as a 2024 or 6061 when the bearings or pins are pressed in on assembly. I think most the Scorpion’s failure’s was because QC wasn’t high enough and the press fit of pins on the tips or the trunnion bearings were to tight. Then under even lighter loads that increased the strain on the rocker body. It ends up causing cracks at the higher pressure points thru the body.

If you want use them for a bigger cam and are still concerned about the strength of the body, I would maybe should consider sending them off and get them cryoed. Probably a good idea for any rocker seeing a lot of abuse.

Didn't know a lot of that regarding the numbers and their specific properties. Thanks for pointing it out. I don't suppose I'll be selling these Scorpion 1.65s to anybody here running an aggressive cam....Lol

[Jay S]

Scorpion made the rockers thicker at the fulcrum tips sometime around 2011. I imagine the rockers Charlie broke the fulcrum on and Cliff’s pictures were both made before that.

None of the Scorpions are my first pick for a big roller cams, I think the Harlan Sharp’s HD rockers are tougher and better quality. Both are USA made though, and for milder street roller cams with less than .6” lift I would run either of those and not give it second thought. Not too long ago I did a Bullet SFT cam for a RA 4 stroker that runs those endurance scorpions.