Push rod 3/8 .145 or 7/16 dual taper?

Finally putting the 501 back together.
A429 heads and modded Vic 460 intake.
T&D rocker bases welded.
Lem spec'd camshaft installed - intake CL at 107 exh CL at 115
Intake to piston clearance 0.080" exh valve to piston clearance 0.110"

Camshaft uses Comp HXL lobe series - reasonably aggressive.
I know a 3/8 0.080" wall push rod will not suffice.
3/8" X 0.135 or 0.145" wall or 7/16 dual taper?


Cheers

If they will fit the 7/16 dual taper are the best.

and what's wrong with a 3/8" x .080" my c-headed 600 spun 8600-9300rpm without a problem or witness marks from defection with 340# seat and 980 open with a .950" lift cam , ti valves mind you
Frank

I built my 600 with C 460 heads before the internet . and it worked !!
Frank

1995 ,hand ported myself , Jon Kaase helped me with the rocker geo
Frank

If you want something stiffer than the .080" 3/8" go ahead with the bigger dia. I don't know about other brands but Trend gets as much or more money for their .135" wall 3/8" as they do for the 7/16" stuff.

Lots of parts/things "work". Doesn't make them the best, most reliable or most desirable.

I run 7/16 on exhaust side.

I have read so much about push rod flex and "pogo stick" behavior with 3/8" 0.080 wall push rods.
Nascar uses huge diameter push rods - with much lower spring pressures than I have - although they certainly are well above my rpm range.
I require new push rods anyhow - the T&D rockers use a shorter push rod than the old Crower stud mount rockers.
Just wanted opinions - and there seem to be many. I do think camshaft lobe design has some impact on push rod suitability.

I think I will stay at 3/8" but use a 0.135 or 0.145 wall.

Thanks all!

7/16 dual taper trend works for me.

Lots of hard running engines are out there with 3/8" pushrods.
Bits and pieces of info over the years has pushed me to 7/16"
intake and 1/2" exhaust pushrods in my last 2 personal engines.
Looks like another dyno shoot-out test when I get either the 645 or the 652 " mule" engines done next year.
An informal test on a BBC that a buddy performed a while back pointed to about 10 hp difference at higher rpm between 3/8 and 7/16".
Is it worth the cost and surgery involved for big pushrods? Just one of those personal decisions I guess.
Later....
Keith

Frank Merkl wrote:and what's wrong with a 3/8" x .080" my c-headed 600 spun 8600-9300rpm without a problem or witness marks from defection with 340# seat and 980 open with a .950" lift cam , ti valves mind you
Frank

Go look at some spintron tests and dyno power differences. The stiffer the better as far as pushrods go and diameter is strong than smaller with thicker walls.

People used to think lightweight pushrods where the ticket too...... Until they learned otherwise. That's long before the Internet !

Spend an extra 100 or more on the special cam, 1500 to 2000 for rockers.... but then use the same ole pushrod that's been bending and deflecting since spring rates exceeded 300lbs....... many of the engines on here should be on 7/16 to 1/2" for the valve mass and RPM they are turning. The extra duration and lift in the cam for that HP is lost in the deflection of the pushrod...........

I'm not so sure that the pushrods' abilities to work within a given valvetrain are based on strength alone. When the pushrod is made stiffer its resonant frequency is increased and this is what makes the valvetrain more stable its not the strength reducing deflection and any pushrod is probably strong enough to have minimal deflection.

DaveMcLain wrote:I'm not so sure that the pushrods' abilities to work within a given valvetrain are based on strength alone.  When the pushrod is made stiffer its resonant frequency is increased and this is what makes the valvetrain more stable its not the strength reducing deflection and any pushrod is probably strong enough to have minimal deflection.

Frequency

I guess I did open a can of worms.

However an important discussion item none the less.

Thanks for all the responses!

Interesting as the wall thickness increases in the 3/8 the frequency comes down.

Called Manton, and had a couple of discussions.
What an awesome company to deal with!
Anyhow went with a series 5 pushrod - 3/8 X 0.120" wall.
Stage 5 uses a 275,000 psi tensile strength material, less flex than the typical 165,000 psi material.
For my rpm (7000 and lower) and with a short lengths (8.430" and 8.410") the pushrod choice should work very well.

I will find out soon enough.

Cheers

I've seen Nascar pushrods that were 1/2 dia for a flat tappet cam! As the Trend chart shows length , diameter , and wall are critical. Noel Manton has forgotten more about pushrods that "most" of us will ever know. I've use his pushrods for almost 40 years now.

With pushrods you have a column. You want column strength. Wall thickness doesn't do what diameter does. You want the largest diameter pushrod in the engine that you can get.

Straubtech wrote:With pushrods you have a column.  You want column strength.    Wall thickness doesn't do what diameter does. You want the largest diameter pushrod in the engine that you can get.

Chris, the O.P. has been told the same ....more than once in this thread. He has done what he has done...let's move on.

Lem Evans wrote:

Straubtech wrote:With pushrods you have a column.  You want column strength.    Wall thickness doesn't do what diameter does. You want the largest diameter pushrod in the engine that you can get.

Chris, the O.P. has been told the same ....more than once in this thread. He has done what he has done...let's move on.

Yes sir!!!!

I have followed the advice from Manton.
I did not decide on what push rod to use on my own or had preconceived ideas. I was leaning towards a 7/16" dual taper before
I talked to Manton.

I provided all the engine build details and rpm range to Manton.
I used their suggested push rod.

Sorry if I can't follow everyone's suggestions. 7/16" would be stiffer sure, - but possibly not required at <7000 rpm?
Manton uses 275,000 psi material for the push rod tube (hence the 3 piece design) Other one piece designs use 165,000 psi
material. Manton told me the 275,000 psi material is stiffer than the 165,000 psi material.

I do appreciate everyone's suggestions and comments.

Cheers!

What you've selected is sufficient for the application, but like we have already talked about bigger is better on pushrods if they will fit in the application.

Straubtech wrote:

Lem Evans wrote:

Straubtech wrote:With pushrods you have a column.  You want column strength.    Wall thickness doesn't do what diameter does. You want the largest diameter pushrod in the engine that you can get.

Chris, the O.P. has been told the same ....more than once in this thread. He has done what he has done...let's move on.

Yes sir!!!!