They say.650 but thats jus a measure of clearance.The seat pressure is too low for the aggressive ramps imo.Maybe with the smaller new cams the Pac's would work but I personally wouldn't chance it till I seen other people run them with single springs.Also rpm range would need to be considered for a given engine when choosing springs..

 

What springs does Comp recommend for those cams? 921's?

 

I really don't know but I would use some patriots extreme's if it were me.Somthin with solid 140+ spring pressure @ the seat.

 

Guess you can't go wrong with a dual spring in this case...high lift and agressive ramp rates. FWIW, I believe that even the Comp 918's and PAC 1218's have 130# at the seat though

 

Pac 1518s are good to 650

 

yea dont think id run these on a DD that sees some miles for valvetrain sake, but thats just me im sure some will disagree. But your right with some decent heads that smaller cam would compare to bigger ones and make some good power with the lobes..