Pushrod diameter question

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FlDart360

FlDart360

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Would there be any Detriment to having pushrods in a 360 LA motor that had a diameter smaller than 5/16? I have owned and driven the car since 2016. Like many on the forum I know little about the history of the motor. I would assume that a larger diameter pushrod would be stronger, but is there anything else I should be concerned about ? I do get foot cramps from time to time , but I have never had the motor above 5500RPM. Does the diameter of the pushrod in anyway affect valvetrain noise?
Thanks.
 
The ends of the push rod matters for the lifter and rockers being used. Pushrods only contribute to noise if they are the wrong length or another part has failed. Strength can come from material selection and the wall thickness as most are hollow. Going larger can cause issues in the pushrod tunnel with larger lifts, rocker location, etc.

5/16 is the stock LA size.
 
The bigger the pushrod, the better. With no exceptions.
That said, all bets are off, obviously if you cant get them to fit.
But assuming you can make a bigger diameter pushrod work, by all means do so.
 
I have found factory mopar push rods in general to be very strong and able to handle a decent amount of spring pressure. The small block Mopar also have a short push rod in comparison to a lot of V8 that also contributes to a rigid rod. Unless you are increasing spring pressure past high performance 340 springs I see no real advantage to going to a different push rod.
 
K.O. SWINGER said:
I have found factory mopar push rods in general to be very strong and able to handle a decent amount of spring pressure. The small block Mopar also have a short push rod in comparison to a lot of V8 that also contributes to a rigid rod. Unless you are increasing spring pressure past high performance 340 springs I see no real advantage to going to a different push rod.
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taking stock, true.
But in a racing application, the thicker the better.
 
I personally have never seen a 1/4" pushrod. 5/16th's is fine for any street engine. As far as noise, a solid lifter cam will always make some valvetrain noise regardless of lash adjustment. If it's hydraulic, they may be too short for your setup.
 
B3422w5 said:
taking stock, true.
But in a racing application, the thicker the better.
Click to expand...

I believe I read somewhere that thicker diameter will be stronger (less flex) than thicker wall. (i.e.: 3/8" x .080" wall is stronger than 5/16" .105" wall.)

Most related parts are designed for 5/16" & larger. Smaller diameter pushrod ball ends would also concentrate more pressure on lifter and rocker arms. Mopar OEM pushrods have been known to punch through stamped non-adjustable rockers when pushed past their limits.
 
I've always wanted to know when the heavy wall push rod becomes a weight penalty.
When does the thick wall of a "higher performance" 5/16 pushrod become too heavy? And I should use a thin wall 3/8 diameter push rod. If that thin wall 3/8 push rod could actually be lighter than the heavy wall 5/16 push rod.
My assumption is that a heavy wall 5/16 could very likely be heavier than a lighter wall 3/8 . I believe that I will keep valve train components as light as reasonably possible ($$.¢¢) in any performance application.
I guess I should order up some singles and find it out.
 
FlDart360 said:
Would there be any Detriment to having pushrods in a 360 LA motor that had a diameter smaller than 5/16? I have owned and driven the car since 2016. Like many on the forum I know little about the history of the motor. I would assume that a larger diameter pushrod would be stronger, but is there anything else I should be concerned about ? I do get foot cramps from time to time , but I have never had the motor above 5500RPM. Does the diameter of the pushrod in anyway affect valvetrain noise?
Thanks.
Click to expand...
Are you thinking about a change because of noise? is there a problem?
 
Bobzilla said:
Steve Morris Racing Engines talking about pushrods.

Click to expand...



He says 3 important things.

1. You can’t get the fuel pump too big.
2. You can’t get the pushrods too big.
3. You can’t get too much ignition.

I agree with all 3 and have said so for many years before this video came out.
 
Locomotion said:
I believe I read somewhere that thicker diameter will be stronger (less flex) than thicker wall. (i.e.: 3/8" x .080" wall is stronger than 5/16" .105" wall.)

Most related parts are designed for 5/16" & larger. Smaller diameter pushrod ball ends would also concentrate more pressure on lifter and rocker arms. Mopar OEM pushrods have been known to punch through stamped non-adjustable rockers when pushed past their limits.
Click to expand...
I’m using .120” wall 5/16” pushrods as I had clearance issues with trying to fit 3/8” with my TF heads. Weighed the pros/cons and settled on those. Thickest I could source.
 
""I’m using .120” wall 5/16” pushrods""
- How much spring pressure are you using with these pushrods?

I too have used them but with only 130lbs/370lbs valve springs with no issues.

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?
 
YO7_A66 said:
""I’m using .120” wall 5/16” pushrods""
- How much spring pressure are you using with these pushrods?

I too have used them but with only 130lbs/370lbs valve springs with no issues.
Click to expand...
IIRC about 180lb/465lb The pushrods are Manley 4130 chrome moly swedged end oiling ball/ball.
 
Keven S. Clickner said:
I've always wanted to know when the heavy wall push rod becomes a weight penalty.
When does the thick wall of a "higher performance" 5/16 pushrod become too heavy? And I should use a thin wall 3/8 diameter push rod. If that thin wall 3/8 push rod could actually be lighter than the heavy wall 5/16 push rod.
My assumption is that a heavy wall 5/16 could very likely be heavier than a lighter wall 3/8 . I believe that I will keep valve train components as light as reasonably possible ($$.¢¢) in any performance application.
I guess I should order up some singles and find it out.
Click to expand...

never too heavy
 
Keven S. Clickner said:
Why so much heavier on the exhaust side?
More lift and or duration on the exhaust side?
Click to expand...

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 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.
 
YO7_A66 said:
""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.
Click to expand...
Cup/ball or ball/ball?
 
dano said:
The ends of the push rod matters for the lifter and rockers being used. Pushrods only contribute to noise if they are the wrong length or another part has failed. Strength can come from material selection and the wall thickness as most are hollow. Going larger can cause issues in the pushrod tunnel with larger lifts, rocker location, etc.

5/16 is the stock LA size.
Click to expand...
Thanks
 
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