1.6 RR high lift cam ~.600 lift

 

I use them on my GM847. The spring pockets will need to be machined. They use the same seats and retainers as Comp 987's.

 

You're asking alot if you're using a cam that isnt billet or especially stock roller lifters. Stock roller lifters only can take I think 135# on the seat reliably, they start collapsing and things like that if you put too much pressure on them. I use 987's and they're fine. Same spring dimensionally. Look at comp's site at the valve spring chart and you'll see some fairly high numbers with the valve open.

IMO dont use them unless you have aftermarket pushrods, better lifters than stock and roller rockers. Consider a billet cam and stainless valves because at those pressures the stock valves are gonna take a beating.