.120 wall pushrods

[ventura74]

Anybody use 5/16 .120 pushrods?

[BlitzA64]

use the 3/8 if they fit. Trend likely would have the length in stock you need.

[sanfordandson]

Diameter trumps wall thickness...

[ventura74]

OK 3/8 it is if they fit so would you go with .080 wall or a thicker wall I understand it depends on spring pressure just looking for some in general advice

[ProPower engines]

What engine?
What cam??

[ventura74]

SB Chevy solid roller.275 in .279 ex at .050 .640 lift 406

[user-612937456]

It depends on the valve-train weight, and over the nose pressure 450-500ish lbs? Hardened .080 wall 5/16 is probably OK. Especially if you have any lightweight components and want good valve-train control. Which comes into play at and above 7000 RPM's

[DaveMcLain]

I'm not so sure that strength has a whole lot to do with pushrod selection. I say it has more to do with the natural resonant frequency of the pushrod with larger diameters and thicker walls and shorter lengths tending to move that resonant frequency higher and hopefully mostly out of the range that can be excited by the frequency content of the lobe and the resonant frequency of other parts of the valvetrain with the RPM range of the engine.

[tenxal]

If you want to stick with the 5/16" push rods, Comp Cams has them in .105 wall thickness. They aren't in their catalog as Trend makes them for Comp. If you want a .120 wall 5/16", Steward Performance has them: http://stewardperformance.com/pushrods.html

I'm using the .105 wall 5/16" Comp/Trends with 425 lb open at 7,100-7,300 in a SBC w/o issue. The 5/16" push rods and adjustable guide plates allows for centering the rocker tip squarely on the tip of the valve stem. With some combinations of 3/8" push rods and guide plates, the push rod holes in the heads get pretty big after being enlarged....not a lot of meat around the edges of the push rod holes.

Hope this helps.

[Frankshaft]

.120 wall 5/16 will work fine in that app. Smith Bros told me years ago, that theirs will handle 750 lbs open at like 12 inches long.

Frank

[Alaskaracer]

.120 wall 5/16 will work fine in that app. Smith Bros told me years ago, that theirs will handle 750 lbs open at like 12 inches long.

Frank

Not without bending like a pole vault pole they won't.... I'm running 7/16-1/2" dual taper, .168" wall on my stuff, 1100 lbs open pressure, longest on exhaust side is about 10.8" long and there are rub marks on the head from the flexing. The don't touch when turned over by hand.

When in doubt, use the largest diameter, heaviest wall pushrod you can fit in your motor. Weight on the lifter side doesn't matter, stronger pushrods only help to stabilize the valve train...I wouldn't run a 5/16" pushrod in anything but a stock application regardless of tubing thickness...

[Frankshaft]

Yah, because you know more than the people that make them

[Warp Speed]

Yah, because you know more than the people that make them

If that is Smith Bros. oppinion (I think your taking their example out of context) then apparently he does!

[Dan Timberlake]

I'm not so sure that strength has a whole lot to do with pushrod selection. I say it has more to do with the natural resonant frequency of the pushrod with larger diameters and thicker walls and shorter lengths tending to move that resonant frequency higher and hopefully mostly out of the range that can be excited by the frequency content of the lobe and the resonant frequency of other parts of the valvetrain with the RPM range of the engine.

=======
Hi Dave,

For shafts, like drive shafts with U-joints at the ends, adding wall thickness while keeping the OD constant //lowers// the natural frequency slightly.

I'd guess the same is true for pushrods of a constant OD.

regards,

Dan T

[69434]

I'm using 5/16 x .120 pushrods without any problems in a 800h.p. sbc