Rocker Arm strength.

[keeks]

Curious on opinions about how much rocker arm I need for 600# pressure at 1.125", running about 7000rpm. Also, will I need to go with 3/8" pushrods, or will 5/16" be ok?

k

[sj valley dave]

600 lbs open, I definitely would go with a 3/8" and a good S/S rocker (Crower) unless you go to a shaft...We run 275 lbs closed 650 open with T&D shaft rockers...

[hpontap]

Howards and Comp both make good aluminum roller rockers that can more than handle 600lbs of open pressure. If the budget allows T&D , Crower and Jesel shaft rockers are the best.

Honestly, Ive built a lot of engines and Ive never had a Comp Magnum 5/16th pushrod break or bend unless something else in the engine let go. Ive had some pretty stout spring prssures running rollers past 8,000 rpm. Remember that a heavier pushrod acts live a heavier valve or retainer. It is still valvetrain weight.

[perfconn]

Lifter and pushrod weight is not near as critical as retainer and valve weight.Thats the reason NASCAR can run 1/2 inch pushrods but run little bitty 5.5mm titanium valves.

[fast_crew]

It's not a matter of the pushrod breaking, it's a matter of valve control, weak pushrods deflect and act as a pole vault to the valvetrain. The days of 5/16's pushrods are about over. Almost any engine will benefit from a stiffer pushrod. Things to keep in mind diameter always trumps wall thickness and .105 is about as thick as you will find 5/16ths. A 3/8 x.120-.135 is what I would run, or a 7/16x.120 if you have the room.

[stockcar5]

I agree with the above. No reason not to run bigger pushrods if they fit. We even found a little hp going from a 5/16 to a 3/8

[hpontap]

Im not here to argue guys. Run what you want and what works for you but, how much do you think those big pushrods benefit the average Saturday night racer?

[perfconn]

Depends on how radical their cam is.If you run a radical cam to make good hp and have to use heavy valves then big pushrods are necessary.

[TBRE]

Im not here to argue guys. Run what you want and what works for you but, how much do you think those big pushrods benefit the average Saturday night racer?

A lot. The more you pound out the valve job, the less life you will get out of the heads. As the valve job gets closer to the short turn, flow drops terribly. Like Phil Coleman always tells me, valvejobing heads is like sharpening a pencil(you can keep sharpening it to a point, but you don't have enough to hold on to). Back in the early 90's, we kept adding valve spring pressure to keep the valvetrain in control, only to make the problem worse, until we started stiffening the pushrods. Like stated above, weak pushrods "polevault" the valvetrain. And, just because an engine didn't blow up, doesn't mean it can't be improved on.TB

[50j]

A lot. The more you pound out the valve job, the less life you will get out of the heads. As the valve job gets closer to the short turn, flow drops terribly. Like Phil Coleman always tells me, valvejobing heads is like sharpening a pencil(you can keep sharpening it to a point, but you don't have enough to hold on to). Back in the early 90's, we kept adding valve spring pressure to keep the valvetrain in control, only to make the problem worse, until we started stiffening the pushrods. Like stated above, weak pushrods "polevault" the valvetrain. And, just because an engine didn't blow up, doesn't mean it can't be improved on.TB

That's right. Getting by and doing it right are different things. I'd go with the 3/8" and feel good about it.