[Steve C.]

Although some degree of pushrod “shock absorbing” is virtually unavoidable, minimizing such deflection and compression is critical for maintaining proper valve timing. Do not be overly concerned about pushrod weight.
The pushrod is on the slow moving side of the valve train. The additional weight of a heavy wall pushrod usually provides a much needed increase in valve train stability.

Helpful. Instead of ordering a 5/16 pushrod with the typical .080"-.082" wall, seek out a 0.116"-0.118"wall pushrod, or similar. Depending on your source. Not much difference in cost.


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[gtofreek]

Originally Posted by Steve C.

Although some degree of pushrod “shock absorbing” is virtually unavoidable, minimizing such deflection and compression is critical for maintaining proper valve timing. Do not be overly concerned about pushrod weight.
The pushrod is on the slow moving side of the valve train. The additional weight of a heavy wall pushrod usually provides a much needed increase in valve train stability.

Helpful. Instead of ordering a 5/16 pushrod with the typical .080"-.082" wall, seek out a 0.116"-0.118"wall pushrod, or similar. Depending on your source. Not much difference in cost.


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^^^^What he said.



The guy who invented the Spintron did it to prove this very thing. He was the founder of Trend Products and made 1 piece pushrods. He made thick wall pushrods and was criticized about their weight. So he built the Spintron and then took a pushrod and welded a piston pin to it and ran it at like 7500 rpm or so, and there was next to no difference at all between it and the pushrod by itself. It is far better to have a thick, strong pushrod that resists deflection, than a light one. It's the valve side of the rocker arm you want to try to lighten up, not the lifter side. Same goes with lifters. People would worry so much about the weight of a flat tappet lifter when it came to racing, but don't think twice about revving a roller lifter that weighs twice as much.

[slowbird]

1/2 pushrods weigh a ton! But they get spun up to 9000rpm and beyond all the time and are very happy

[Cliff R]

"It is far better to have a thick, strong pushrod that resists deflection, than a light one"

+2 and why I equip my engines with .120" wall pushrods instead of .080". The deflection with "standard" .080" stuff is considerable, as I found out messing with that sort of thing quite a few years ago. I'd go to larger diameters instead but that's a bit more difficult in the big scheme of things.......Cliff

[TCSGTO]

One of the disadvantages of a Pontiac is it’s pushrod length. The long pushrod is going to deflect. No getting around that.
Since column strength depends much more on O.D. than wall thickness, .118” 5/16 pushrods helps stiffness a little compared to .080” but not nearly as much as going to 3/8” would. I always wanted to try some tapered pushrods that are thicker at the lifter end where the most deflection occurs but the co$t always stopped me.

[Cliff R]

Correct and larger diameter still at .080" wall would be better overall than .118-.120" at the smaller 5/16" diameter, but much more difficult to accomplish in these engines from a builders standpoint......

[HWYSTR455]

The Smith Bros pushrods are great, one piece, have minimal deflection, one of the best out there for the money. Never had an issue with them. Butler carries them:

https://butlerperformance.com/c-1234...-pushrods.html

They have 3/8 ones too, but are mainly overkill for anything less than X spring psi/RPM.

To some degree, pushrods should be sacrificial, to save parts in a failure-type incident. So some flex is acceptable in that case.


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[Steve C.]

Not as an endorsement for the 3/8 size. However for interest in relation to the comment made by TCSGTO. Here is the communication between myself and Manton techline on the subject:

My message:

"First, I have been using your pushrods for years and very pleased with your service and product. This inquiry is general in nature and for interest on my part. Thus I'm not seeking specifics. Given the same length how much difference in "strength / deflection" is there between a 5/16 diameter with a 0.118 wall compared to a 3/8 diameter with a wall section at or near .083."

Their reply as sent to me:

"If you were to build a 5/16 pushrod and a 3/8 pushrod at the same length and same diameter the difference in column strength is 96.7 percent different
if you go up in wall thickness from say .083 wall to .118 wall only about 5-6 % better so always go with larger tube if it will fit."

Their wording is a bit confusing. I question are they are suggesting going from a .083 wall to a .118 wall on a 5/16 dia push rod it's about 5-6 percent better. But not sure.



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[HWYSTR455]

I think they meant to say same length and same wall thickness, you cant build a 5/16 diamter rod in 3/8 thickness. Because, it would be a 3/8 diamter rod at that point.

But i get the point. Brings up the question now of how much deflection there is, in relation to lift potentially lost.

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[Steve C.]

Personally I use Manton 5/16 with a .118 wall. I believe Comp lists all their 5/16 as .080 wall, but I have read if you want a 5/16 ordered thru Comp with a thicker wall they get them from Trend Performance who makes their 5/16 with a .105 wall.
Manley Performance makes 5/16 with a .120 wall. Smith Brothers makes 5/16 in a .116 wall.


"If you all would just spend a day on the Spin-tron, there would be no question.
You would all be running the stiffest pushrod you could fit in the engine, and you would care nothing about the added weight."

Mike Jones
Jones Cam Designs


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[AG]

Smith Brothers recommended 3/8"-0.083" wall PRs over 5/16"-0.118" for my race motor that has 680# open pressure. I use Pro Series ARP studs and a Jomar girdle and the valvetrain feels rock solid.

[Formulas]

Soooooo anybody press a responsive pushrod company for a 11/32 dia. Thick wall pushrod?

RAIV used 11/32 it wouldn't be that hard to modify say Edelbrock pushrod guides to accommodate

Think outside the herd
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[TCSGTO]

Originally Posted by Steve C.

Their wording is a bit confusing. I question are they are suggesting going from a .083 wall to a .118 wall on a 5/16 dia push rod it's about 5-6 percent better. But not sure.

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Yes. Adding .040” to the wall of a .312” diameter tube has little effect on stiffness. Every little bit helps though.

[slowbird]

Originally Posted by Formulas

Soooooo anybody press a responsive pushrod company for a 11/32 dia. Thick wall pushrod?

RAIV used 11/32 it wouldn't be that hard to modify say Edelbrock pushrod guides to accommodate

Think outside the herd
.

They make 3/8 not worth it to them to do 11/32 and if they did it would cost!

[Formulas]

"They make 3/8 not worth it to them to do 11/32 and if they did it would cost!"

So you don't know because you haven't asked or know how much more .. nice post

[slowbird]

Originally Posted by Formulas

"They make 3/8 not worth it to them to do 11/32 and if they did it would cost!"

So you don't know because you haven't asked or know how much more .. nice post

Here you go order away
https://www.summitracing.com/search/...rder=Ascending

[Cliff R]

Larger diameter pushrods have always been available, but they require wider guideplates and clearancing per application.

I've got large diameter pushrods on several full race applications with high port heads, big power levels, heavy spring loads, and spin pretty high RPM's. For most street applications the cost and pain vs gain is not worth the additional effort....IMHO.....Cliff

[tc]

Since it was raining at BOP day in Cordova and I saw the announcement of 1/8 mile, I headed to Earlville.

First 2 runs, same as before, 12.33, 12.33 at 108.4 mph

Put smaller jets in the 9380 Holley, 2 runs, 12.23, 12.26 at 108.9 mph

The 9380 has a choke tower and I have used a Mr Gasket stubstack for many years. The metal K&N air cleaner top is cone shaped with the center higher than the 14 inch outer diameter. At the outer diameter of the stubstack, there is 1 inch of space to the lid. At the center there is 1/2 inch more down to the top of the stubstack.

I took the stubstack off and the next 2 runs were similar to each other.

60 ft 1.632
1/8 et 7.56
1/8 mph 89.3
1/4 et 11.97
1/4 mph 111.6

I was excited and am happy the 60919 delivered. Not sure if removing the stubstack, letting the float bowl vent tube be non surrounded helped any. I'm sure now that 1 inch of space is not enough for air flow.

I did not get to vary the shift rpm, shifted at 5700.

Now I feel dumb for not removing the stubstack with my old cam to see if the 11.8's could have been 11.6's.

My friend has a Q series drag race Quickfuel 850 with the contoured air entrance. Maybe I should buy that and learn how to make changes to a Holley carb, air bleeds, etc.

[TCSGTO]

Congrats! It always feels good to make gains like that.

The stub stack might work if you don’t run an air cleaner. I bought one of those when they came out after a pretty well known auto scribe claimed they were good for 20 Hp through his extensive “unbiased” dyno testing. Turns out he was behind the marketing of them and profited nicely from K&N selling them. My results were pretty much like yours.

[ponchorob]

Tc any further improvement with crower 60919 from 11.97 at 111.6mph