I'm looking at swapping the rockers on my 305 TPI to full roller. It has a ZZ4 cam, Comp CM rods and stock iron heads (will swap in 305 TFS heads later).

Which would be the better choice, Comp Magnum Pro or Scorpion Alum.?

Is there any difference?

Thanks

 

NOT SURE BUT IM SELLING MY SCORPION ONES 1.6 YELLOW

 

The ultra pro-mags are a better and more durable rocker. As theyre made of steel, they have a larger trunion, and dont suffer from metal fatigue that the aluminum ones do. Aluminum does not have infinite fatigue life like ferrous metals do. Given enough time, aluminum rockers will fail.

I have a set of the ultra pro-mags, and so far, theyre very quiet and seem to work quite well.

 

Ferrous metal? The Comp Cams pro mag or whatever they're called now is stainless. Still much better than any aluminum rocker. Less weight on the valve.

 

The Pro Magnums would be the choice in a street application.

[QUOTE=dimented24x7;5132059]The ultra pro-mags are a better and more durable rocker. As theyre made of steel, they have a larger trunion, and dont suffer from metal fatigue that the aluminum ones do. Aluminum does not have infinite fatigue life like ferrous metals do. Given enough time, aluminum rockers will fail.QUOTE]

Precisely.


Stainless steel IS a ferrous metal.

 

Thanks for the advise everyone. I'll be ordering a set of the Comps next week.


Might go 1.6 on the exhaust.

 

I wouldn't hesitate to go 1.6 on the intakes too.

 

How much more lift would that give me? ZZ4 is .474 and .510

 

Intake at 1.6 is .506
Exhaust is .544

I'd certainly be checking all the appropriate clearences when making the upgrade.
Especially on the stock heads.

 

The ultras I got where chromoly steel with a black oxide coating, but I think they come both ways.

 

The only thing I can say is, as with any part, make sure to thoroughly clean them in mineral spirits. Also spin the trunions around to make sure you get the needle bearings 100% clean and de-greased. The grease grabs a lot of metal filings during production. When I cleaned mine, a lot of crap came out of them. When done and dry, just soak them in oil for start-up.

As for the extra lift, make sure the springs can take it and you have enough clearance if you use 1.6's. The standard ratio is 1.52, so they give a slight increase in lift by themselves, and will give a noticiable increase in lift over standard stock stamped rockers since they dont flex.

 

Good advise on the cleaning.

I might go 1.6 on the intake. Can't go 1.6 on the exhaust as the ZZ4 springs are only good for .540 lift.

Still better than stock.

 

He also means to check that the reduced retainer to guide boss/seal clearance will be adequate.

 

...and coil bind as well as retainer to rocker arm clearence.
Don't forget proper geometry either. 1.6's can move the rocker tip off the valve stem.