Pushrod diameter question

[FlDart360]

Are you thinking about a change because of noise? is there a problem?

No, I just was surprised to see something other than a 5/16 pushrod, and was curious why someone might do such a thing.

 

[Bobzilla]

""Is anyone using the 5/16" (heavy wall, Manton Grade 3 or Manton Grade 5) pushrods on solid roller valve springs (220lbs/540lbs) for reference?""

I just got a reply from Manton on which size of pushrod they would recommend for a spring spec of 230lbs/540lbs, @ apx 7.850" long and 6400rpms. They recommended their 5/16" x .118" in a 5 series [275k psi], or the 11/32" x .120" in the same series would deflect 53% less under the same load.

Wow, 53% less deflection from what appears to be a small increase in diameter and wall thickness. That speaks volumes.

 

[Keven S. Clickner]

More room. The cam i ran those with was actually 699/672
Pushrod weight isn't a factor. The bigger diameter pushrod doesn't weight as much of a percentage heavier as you would think. And its way more than negated by the stability it creates.
In short, in any performance application, jam in as big a pushrod as will fit

Is there an issue of harmonics then?

 

[Rat Bastid]

Is there an issue of harmonics then?

Yes. Pushrods flexing will induce every manner of harmonic you can think of. I’ve seen it make an oil filter unscrew and fall off.

 

[Keven S. Clickner]

""Is anyone using the 5/16" (heavy wall, Manton Grade 3 or Manton Grade 5) pushrods on solid roller valve springs (220lbs/540lbs) for reference?""

I just got a reply from Manton on which size of pushrod they would recommend for a spring spec of 230lbs/540lbs, @ apx 7.850" long and 6400rpms. They recommended their 5/16" x .118" in a 5 series [275k psi], or the 11/32" x .120" in the same series would deflect 53% less under the same load.

Wow. 53% is a big number. Now I want to know what that deflection is at speed. Measured to the thousandth of an inch.

 

[Keven S. Clickner]

Yes. Pushrods flexing will induce every manner of harmonic you can think of. I’ve seen it make an oil filter unscrew and fall off.

There used to be a television program called That's Incredible.

 

[MOPAROFFICIAL]

My next build... I'm custom fitting sections of metal coat hanger in for push rods... Going for the ultra light valve train...

But on serious note.. I run 5/16 Smith bros @.080 or so thick wall w/220-480lbs and I'm liking the sound of those 11/32.... less clearancing for that roller buddy!