Pushrod Tech question .

[Alky V6]

I went with 3/8 to 7/16 single taper pushrods. In the world of pushrods 9 inches is pretty long and the longer the pushrod the more likelyhood of flexing or flexing caused by frequency vibration. Kind of like driveshaft lengths. If you go too long with a driveshaft of a given material and diameter, you can get natural frequency vibration at a relatively low turning speed. This vibration can be bad enough to destroy the driveshaft. Same thing can happen with pushrods. I don't know at what spring pressures and rpm this would occur, but the chance is there, particularly with the long pushrods the Buick V6 must use. Putting a taper in a pushrod, whether single or double, upsets the natural frequency limit, making for a more stable valvetrain. I've heard the same thing about weight on the lifter side being less important than weight on the valve side of the rocker. I also use .903" OD lifter bodies which add even more weight to the lifter side. Redline is 7800 rpm. Shift point is 7200 to 7400 rpm.

 

[TurboTR]

Another good vendor for racing push rods is Manton Racing. A single taper can be a good choice to also help get through the smallish passages in the heads. Manton 4140 are more expensive than generic 5/16, but well worth it. The exhaust side in particular takes a beating (much higher load to push the exh valve open initially), and they can/do leave big divots in the head gaskets where they poke through into the lifter valley. That has to be on the order of +/- 1/2" of flex at least. And that even with just a mild hydraulic flat tappet application at < 6000 rpm. It'll run like that, sure, but clearly alot of room for improvement there..

Still have a set of Manton 4140 laying around if anyone's interested. Went with single taper 3/8 -> 11/32 on the exh side, straight 11/32 on the intake. Application was an S1 with GN1-R heads, so they'd be great for a stock block type application (ie stock deck height rather than S2).

TurboTR