Pushrod comparisons

Hamilton Cams

Hamilton Cams

ignorant
Joined
Jun 28, 2007
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The pushrod is a very important and often overlooked component in any high horsepower build. It doesn't have to do a much, just transmit lift from the lifter to the rocker arm, and bend or deflect as little as possible. Reducing mass in an engine is almost always a good thing however there are a few places, in order to work correctly under high stress, that require a super rigid part. The problem is that more rigidity almost always means more mass. In these applications that require a super rigid part, pushrods, rods, wrist pins etc., to reduce mass would be to get a part that either doesn't live long, or a part that reduces performance. This is where pushrods fall. There are ways to get a strong part with better design and better materials without gaining mass in some instances. But that mindset too often means one-off designs and exotic materials, and that means a lot of money. In the pushrod world there is a small group of materials that work best for the given mass. Mainly performance pushrods are made from a form of chromoly. Ours are no different being made of 4130 chromoly with hardened 8620 pressed in ends. I hear a some concern about pushrods and weight, but I can assure you the negatives of additional mass are more than out weighed by the benefits of having the valve open at the correct time, having the valve stay open longer and the additional lift gained fom no deflection(bending). The pushrods in street driven cummins are just a fraction of the weight of nascar pushrods that spin more that double the rpm's of a cummins. Nascar teams spend millions on engine design and research supports a more rigid design with more mass. Hamilton pushrods are manufactured by the same company that builds for many of the top teams internationally in all forms of racing. We have spent many hours designing and comparing with every "performance" diesel pushrod on the market, and I will show you with real data how our pushrods are the best on the market.
 
1)The first place to start is to use better materials with a slightly thicker wall. We use .095 +/- thick 3/8(.375") 4130 chromoly for our entry level pushrod. We also use 8620 pressed in ends for a super long life under high stress.

2)The next way to get a more rigid pushrod without gaining much mass is to have a larger outside diameter. But sometimes this creates problems with cylinder head clearance if there is a super high lift cam or higher ratio rocker arms are used. We provide 7/16(.437") for engines used mainly in racing or sled pulling. Custom order in any length.

3) If there is clearance problems in the engine but a better piece is needed the next option is a reverse tapered pushrod. We offer these for 12v and 24v where additional clearance is needed. They are 7/16(.437") at the base and 3/8(.375") at the top near the rocker arm. These are also a custom order piece.
 
I assume you are only talking about pushrods marketed by "performance diesel" companies?
 
Sorry to keep you waiting guys, I had to get a bite to eat. Also my intention is not to bash any vendors, but to show how were doing all we can to make the best products possible. Sinner, I am not so ignoratnt to think that a better pushrod can't be made by somebody out there. We can also go pretty mean if somebdy steps up to our 7/16 and even 1/2" but it is not feasable weight wise, and there is not enough room in all engines. Again not bashing any other manufacturers, for comparison purposes I bought a set of everybody elses that I found marketed to the general public. Also I spoke to at least 20 different manufacturers before I settled on this manufacturer. wunderwood I have seen 10-15 bent into an S shaped and heard of a lot more. But really that has nothing to do with the case for better pushrods. The main reason we have uprgraded pushrods is that the factory pieces deflect before they open the valve, which reduces lift, and retards cam timing. Which in turn reduces airflow. The main culprit is the exh. pushrod. it has to overcome phenominal cylinder pressure, especially on trucks over 500 hp. Check out some of the info I have collected you make any conclusions"



Lets look at wall thickness, O.D., material, and load buckling weight(using Uhlers equation for column strength in steel columns with moderate sideloading) first, then design. This buckling factor is the approx. weight in lbs needed to buckle a steel column. In the first picture from left to right factory,brand x, brand y, Hamilton 3/8, Hamilton 7/16



factory, X, Y, HD3/8 , HD7/16

wall thickness-.075", .041", .083", .095", .168"
O.D- .375", .313", .375", .379", .437
material- mild steel, chromoly, chromoly, 4130chr, 4130chr
Buckle weight- 1794lbs , 741lbs., 1982lbs, 2064lbs, 4035lbs


This buckling weight is the true measure of strength in a pushrod. Also the common nascar p.r. is .437" with .120" wall, some even use .500" .168" and spin over 10,000 rpm. Mass should be of no concern in this particular instance.


Next is design.

The .041 with spot welded on ends would have no place in my engine seeing as how I can bend them a good bit with my bare hands. They have more than a 1000lbs less buckling strenght than a factory p.r. Wow! That actually makes me angry that somebody is selling these as a "Lighter" performance pushrods. the next problem with this p.r. is the fact that rather than to spend money on tooling to make the 10mm(.03937")balls and cups on these comparable 24v p.r. all of the units I bought had common gasoline
3/8"(.0375") ends and cups which don't fit the cummins lifter or rocker well however they will work, but have play.

Brand y had a few areas for concern. Material is good quality as was finish. It is alittle thinner but very comparable to HD.095 in terms of column strength. The main concern is that the ball end is just a formed and heat treated part of the pushrod no pressed in end. Both ends are the wrong diameter as you can see from the wear pattern on the black pushrod. The last area for concern is the hole in the end, this poses two problems. One, since there is already less surface area contacting the lifter, this could potentially cause wear issues downline. The second, is that because of pumping action of the p.r., it fills with oil which adds mass to the valve train.


I have spent a lot of time to give honest comparrisons to all the p.r. which I found on the market. My reason for posting is nothing other than I am backing up the fact that I do exhaustive research to make sure that I have the best products to offer the public. If my intent was to bash others I would just post the names of the other manufactures and pictures, not spend days in research. Also there are other well known "manufacturers" out there. I did not include them because they are selling reboxed Hamilton P.R. With the airflow issues the cummins has, it is important to address any area where gains are possible. Thanks for your interest in this article. The next post in a couple of days will be about exhaust lobes." Spoolup vs. torque efficiency vs.emissions, when to open the exhaust valve"


thanks,

Zach Hamilton
 
Last edited:
wildmanben said:
You going to answer the question or just tell us how yours are so much better than everyone else?
Click to expand...

Sorry, thats not the way I intended it. Been a long night already. I know Zach is working on some sweet products for us. Just seemed like he was giving a big presentation and not addressing a few questions. So anyways. Carry on and keep doing what your doing!:Cheer:
 
im thinking a nice hamilton cam and set of p.r. would go nicely in my motor this winter!
 
No prob wild man ben, but if I was just telling you my stuff was better without supporting data it would look more like this

"Its funny to see others come along and tell us how we have a product that is less than others in terms of performance, etc when we were the first of any 24 valve ( VP and CR ) to test drop in springs for higher RPM, boost and back pressure

I can tell you all that the F1 springs are more than needed using stock retainers, collets and valves without a worry of failure of those factory components. The pressure used is slightly higher now than it was in the early days, but not as much as others. " -donm


It is funny but it has worked for years.
 
can a cam and pushrods be ordered directly, or only through your dealers? i need some pricing!
 
I would like pricing also...your article speaks directly to a soon-to-be (or want-to-be) engineer. After seeing the cross sections I am sold, I also found it interesting that they do not use the exact ball end we need but a similar, more common one, with play. Pm pricing please for a set of pushrods for 01 dodge 24v.
Thanks,
Alex
 
So in the cases where they were bent , where would the weak link have been moved to if your HD pushrods were already in place ?
 
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