z28crazy

Ive gone and done it. Blew the top end. bent a valve, broke three rockers, bent two push rods and broke 4 springs all on one side. this sucks.

My question to anyone with good product knowledge is what can i replace it with. I have a high lift cam, carb, and forged bottom end. I really need a top end that will handle high revs (65-7000 range just in case) but wont be heavy and produce good power. i would like your input on specific parts for rockers, rods, springs and valves. if more info is needed i will gladly provide it.

five7kid

iTrader: (14)

Did you over-rev it and float the valves? If not, you probably have an interference problem.

Comp 981 springs and 750 retainers will handle that lift. Make sure your retainer-to-guide clearance (including stem seal, if using a type that goes over the guide) is at least .060" more than your valve travel.

Comp Pro Magnum rockers are great pieces. You don't need anything fancy for pushrods. Are you running guide plates?

Proper assembly of the heads is critical. You don't want a standard production job when it comes time to do that.

z28crazy

Yea i did over rev it a few times....the over revs contributed to spring fatigue which killed the motor when i was just cruising. i am not using rod guides. should I? For the rockers and springs do you have part numbers?
I keep reading about seat pressure for springs? What should i be looking for? or what does that refer to? Will a higher seat pressure prevent valve float? or will it make it harder for the motor to rev up?

those pro magnum rockers are alot better and lighter than the steel stamp stuff?

five7kid

iTrader: (14)

I couldn't see your sig while I was typing. Still running '90 Vette heads? Should be aluminum 113's (or similar), which if I recall have pushrod guide plates. Either that, or self-aligning rockers, I'm not sure which. If the pushrod holes are round and substantially larger than the pushrods, you need one or the other. If the pushrod holes are oval with the width just barely bigger than the pushrods (never heard of that with aluminum heads), you can't use guideplates or self-aligning rockers.

The spring p/n is 981. You get 16 of them with p/n 981-16. Do a search on www.summitracing.com, they'll come up. Same with the retainers, 750-16 for 16. A similar search for the rockers (Pro Magnum) will give the p/n for them. The Pro Magnums are significantly superior to stamped in all ways except price.

Seat pressure (a misnomer) refers to the force the springs exert on the valve when the valve is closed. In other words, to compress the spring to the installed height will take xxx pounds of force (like 120 pounds). Open pressure (again, a misnomer) is similar, but the force at the full open position. You want to follow the cam manufacturer's recommendations for seat and open spring pressures. More doesn't help and increases wear (doesn't significantly make it harder for the engine to rev), less leads to valve float.