Hey all, I have a 350 with the gmpp #24502476 cam with 212/222 dur. @ .050, .435/.460 lift, 112.5 lsa currently in my engine, the #4 exhaust lobe has started to flatten so I'm looking into getting a replacement roller cam. I looked on comps website and found the comp cs264h-r12 cam which has 210/220 dur. @ .050, .480/.480 lift, 112 lsa, this is the cam I would LIKE to run but I think .480 lift would cause some clearance issues with my stock valvetrain and my heads (217 heads) would need machining on the guides to have everything clear, maybe it wouldn't but I don't wanna find out the hard way.

I was doing some research and I found the SUM - 8800 cam, it has 204/214 dur. @ .050, .450/.450 lift, 112 +1 adv lsa. This I KNOW for sure will work very well with my stock 217 heads, it has comperable lift numbers to my current flat tappet cam however there is less duration @ .050. How much of a performance difference can I expect between my stock flat tappet and the SUM - 8800?

I was told the way you compare a flat tappet and roller cam is you take the roller and add 6 degrees to the duration at .050 to see its flat tappet equivalent, which means the sum 8800 is actually VERY close to my current cam right?

 

Forget about all that. Wrong way to look at it.

You DO NOT want to run a flat-tappet cam in 2025 if you can help it. PERIOD. Oils currently available, that you can just go to yerbasic local store and actually buy, do not support that system properly anymore. Witness your one lobe failing already. Put another flat-tappet cam in it and there's a good chance you'll be RIGHT BACK where you are now before you realize it.

Upgrade your valve train. All you need is LS6 type springs and the Comp "adapter" retainers (787) with their matching hardware, set up to the stock LS motor height (1.800"). Run the better cam. Problem solved.

 

when I upgrade the valvetrain what valve seals should I run? I currently have the stock positive stop on the intake and umbrella on the exhaust

 

Run those on all the valves. NOT "umbrella" type. No need to bother with the O-rings in the retainers.

 

Will I be able to run the FEL-SS72861 seals? I thought my heads would need to be machined to accept positive stop seals? I have 217 heads, same as 083 heads

Also thank you so much for the info I really appreciate this a lot, can’t wait to get back on the road soon

 

One of these things is not like the other?

Measure your guides to be sure. Those stock seals are for guides that are about .550" OD. Which is about what stock ones usually are.

 

oh I meant on the exhaust valve only, I thought the exhaust valve would need to be machined I should’ve clarified, I’ll measure it like you said to be sure