Like most people I read the mags, and I recently saw a vortec headed SBC crank out 450HP on a dyno in the mags. I think its around 425 but thats beyond the point.

On old chevy heads there were no guide plates or self-Aligning rockers. Where did this need come for these self aligning rockers?

What is different that makes the vortec heads have to have these rockers vs the standered camel hump head.
Does the pushrod slop in the pushrod hole or what. I have still heard you have to machine the slots for 1.6 inch rockers so they cant be that much different from the old heads. I just cant reason why I need some new part when the old chevy heads that I ran for many moons ran fine and damn good.

I dont think they have changed pushrods from 5/16 right? I know the lengths have switched for the roller block engines but Im not gonna run a roller.

Is this GM blowing smoke somewhere to sell more parts or is there a reason to use these "High Tech" rockers. Honestly its the same rocker with to tits where the push rod goes.. The pushrod never used to fall out of the old engines, and they RPMed alot better than a 5.7 truck engine.

Thanks

Moe,

I drill my factory heads pushrod holes out myself for 1.6 rockers, it's easy to do yourself and doesn't take much time. Yes run 5/16 pushrods, the 3/8 pushrods are just extra mass and weight that you don't need. Trick flow pushrods are excellent product and come in various lengths to correct geometry problems after machining the block and heads. Don't use pushrods with pressed in ends. I've run stamped steel rockers well beyond 8,000 rpm many, many times on 302s and never had one fail. I don't see the need to build in extra complexity. Don't run 1.6 rockers without screw in studs and good springs, expecially critical on the exhaust side since this gets stressed the most due to heat and opening during the exhaust stroke. On the small block it's the two center exhaust valves that you've got to watch the closest, there isn't enough cooling there. This is where the old double hump heads often crack.

The older "non vortec" heads used machined guide slots in the heads (where the pushrod passes thru the head). The vortecs don't have a machined guide in them...where the pushrod passes thru the head is now just a drilled hole, thus the need for guided rockers. Or, machine them for screw in studs and guideplates.

I'm not really sure of the reason for the switch to self-aligning rockers. A couple that I can speculate are: 1- Reducing the amount of cast iron in the head, thus, less weight. 2-Eliminating the machining process for the pushrod slots = less cost. 3-Without the pushrod slots, there is ro friction between head and pushrod. Although any friction would have been minimal to begin with. Any other ideas?

When using a hydralic lifter cam the pushrod is bottomed out on the rocker so how can it slip out even if the head allows for more movement. I dont think it is the head holding the pushrod in place, I think it is a combo of the rocker arm/ lifter. If the head was holding it tighty it would make to much friction and pushrods would fail. The only wear parts on a pushrod I have ever seen are the top and bottom. I might have to try it, but I dont wanna be out alot of money because im stubborn.

Its like a piece of steel, you support it on both ends so it cant excape, its nice to have support in the middle too, but its not manditory. I dont see how too tits on the rocker keep it from wondering around better than an old school rocker thats fitting well. I want to run 1.6/1.5 rockers on a vortec headed 355 because the intake lift is so low, .439 inches of lift. Its actually the old LT1 cam, that has a great exhaust design, I guess I would be better off porting a set of 186 if I can find some.

The purpose of the new self aligning rocker arms is to keep the rocker from rotating on the stud side to side. Guide plates do the same thing.

On older heads, the hole that the push rod passes through in the head accomplished this - it is not a hole but a slot that lets the push rod move towards and away from the rocker stud but not to the side. On some heads you have to elongate this slot for 1.6 rockers because the push rod moves closer to the stud than with stock rockers.

Heads that have holes, instead of slots, for the push rods require some other way of preventing the pushrod from moving side to side and the rocker rotating around the stud. The guides plates, and now also the self-aligning rockers accomplish this.

Moe396, if you look at a set of used pushrods, you'll see a shiny area where it passes through the head or the guide plate, where it has rubbed.

Ray