Pump/Pushrod Ponderings...

[moparedtn]

Yes...since that pushrod end is riding on a lobe, like a lifter does, it could be ground into oblivion if that eccentric lobe wasn't finished properly....I'd say the odds aren't terrible that that's the cause of at least some of the failures.

I wonder (and maybe one of you metallurgic-type folks know this) - original equipment, was the intent of
the engineers for the pushrod to be harder than the cam or vice-versa?

 

[beanhead]

Here is my last experience. Bought 3 "suposedly" nos rods. Bought from a guy who only sells old stuff, so I really have no reason to doubt him. This is with about 1200 miles of use.

View attachment 1171526 View attachment 1171527 View attachment 1171528

Yeah, I know that story unfortunately...hopefully that OEM rod will live to a ripe old age for you!
What's curious to me is, with that much material ground off, was there still enough preload/contact to keep the pump 'pumping'?

I wonder (and maybe one of you metallurgic-type folks know this) - original equipment, was the intent of
the engineers for the pushrod to be harder than the cam or vice-versa?

Excellent question. I know (or rather have been told by people in the industry) that the bronze-tipped rods are supposed to be a "sacrificial lamb" of sorts with the billet cam cores...they want the rod to wear first. Same thing with the distributor drive gears.

 

[moparedtn]

Excellent question. I know (or rather have been told by people in the industry) that the bronze-tipped rods are supposed to be a "sacrificial lamb" of sorts with the billet cam cores...they want the rod to wear first. Same thing with the distributor drive gears.

I guess that makes sense - making the easier-replaced items be the "wear" ones.

 

[Kern Dog]

I could work it by hand without too much fuss but it was stiffer than the factory pump, so maybe they aren't making them like they used to?

I was thinking that the last one I installed might have been siezed inside since I could not press the lever with my thumb.

 

[moparedtn]

I was thinking that the last one I installed might have been siezed inside since I could not press the lever with my thumb.

Don't know, but the repro Carter "hemi" pump I got from Mancini was like that also - sucker was stiff.
No way you were gonna work it by hand.

 

[khryslerkid]

Don't know, but the repro Carter "hemi" pump I got from Mancini was like that also - sucker was stiff.
No way you were gonna work it by hand.

In the past I would clamp them in a vice to test them. Maybe a body builder could do it by hand but most had a little more resistance than that. If I could do one by hand normally ment they were shot, just like a worn out shock absorber.

 

[moparedtn]

In the past I would clamp them in a vice to test them. Maybe a body builder could do it by hand but most had a little more resistance than that. If I could do one by hand normally ment they were shot, just like a worn out shock absorber.

Exactly. If I pulled one off a car and it moved by hand, I figured it was shot.

 

[hunt2elk]

Yeah, I know that story unfortunately...hopefully that OEM rod will live to a ripe old age for you!
What's curious to me is, with that much material ground off, was there still enough preload/contact to keep the pump 'pumping'?

I was at the end stages of tuning my new motor/carb. I was starting to get a bit more valve train noise and on my last couple of wot's, I noticed it didn't have as much power as it used to. Ran fine everywhere else though. That's when I pulled the pump and found the worn rod. Put in the one you sent me and ran it just a few miles before the valve train noise started getting worse. Pulled the valve covers and found issues that I posted another thread about. Still waiting on new lifters from Johnson, so unfortunately the motor is still sitting apart.
On another note, I still have the other 2 "nos" rods. If anyone has a way to test their hardness, I will drop them in the mail. I'm curious as to what they really are.

 

[twecomm]

11 yrs ago at 88.5 K miles, started having fuel delivery issues. Pump push rod was worn by 3/8". , barely stroking the pump arm.
Replaced and that solved everything. Got the new replacement at local non chain parts store where owner is luckily a fellow Mopar guy. When I had this problem 11 yrs ago, I read more than a few threads when Googling the issue, indicating how Chrysler back in the mid 60's had a run of fuel pump rods that were hardened improperly that made it into many cars on the line before being discovered much later. No way to know if it's true or not or BS, but mine was original and they do wear.

 

[BeepBeepRR]

11 yrs ago at 88.5 K miles, started having fuel delivery issues. Pump push rod was worn by 3/8". , barely stroking the pump arm.
Replaced and that solved everything. Got the new replacement at local non chain parts store where owner is luckily a fellow Mopar guy. When I had this problem 11 yrs ago, I read more than a few threads when Googling the issue, indicating how Chrysler back in the mid 60's had a run of fuel pump rods that were hardened improperly that made it into many cars on the line before being discovered much later. No way to know if it's true or not or BS, but mine was original and they do wear.

While that may have been true then. It doesn't explain the latest push rods and how they wear out. Either its a cam issue, or its a hardening issue or both.

 

[hunt2elk]

When I had this problem 11 yrs ago, I read more than a few threads when Googling the issue, indicating how Chrysler back in the mid 60's had a run of fuel pump rods that were hardened improperly that made it into many cars on the line before being discovered much later. No way to know if it's true or not or BS, but mine was original and they do wear.

That would really make sense concerning the 3 nos ones I have. The guy said they were from the early/mid 1960's.

 

[beanhead]

Exactly. If I pulled one off a car and it moved by hand, I figured it was shot.

....I don't know about that, I've always 'bench-tested' them by moving the arm by hand--and I'm definitely saying not they're 'easy' to move and I didn't mean to imply that--but two or three strokes was do-able while holding a finger over the inlet to feel for suction. And yeah if they moved too easily, didn't have a good suction or make that good popping noise, into the garbage they went. And I sure don't doubt what you and 'Kid are saying, but that may point to pumps not being made to the same standards.


Great discussion folks...I don't know if it makes life any easier knowing there's reason to doubt three parts instead if just one, but it's all good knowledge. Especially if someone's having multiple failures, it gives something else to think about.

 

[Dajkzo]

A little more searching and I found that Hughes sells their own fuel pump push rods. The model for flat tappet cams is :https://www.hughesengines.com/Index...YnMp&level2=TWlzY2VsbGFuZW91cw==&partid=10201

They are specific about it being heat treated 4140. And they have a bronze tipped part for billet steel cams. I'm building my 440 this winter and had planned on using the Carter street/strip mechanical pump, so I'm going to order a pump rod from Hughes. Mancini also sells the hardened Hughes rod.

I made a phone call to my Godfather, who while not being a mobster, knows just about everything when it comes to tool and die work. His family had a mold-making business for two generations. When it comes to 4140 and 8620 alloys, the heat treatment is very specific so you get the proper hardness and retain the tensile strength. If the hardness is not deep enough, the surface will fail when the core deflects. Once the surface is compromised the part is history. And just the opposite if the hardness is too deep and the tempering is wrong. And for a bronze tip he said an alloy like Ampco 45. Uncle Bob is in his eighties and still has a 57 Vette. I mentioned the cam shaft issues and how we all use an oil with enough ZDDP and his answer was "early failures point to the manufacturing error because he's had an #!!@^%$RF%! aftermarket cam in his 327 since the late 1970's when he had the engine built."

 

[moparedtn]

I was at the end stages of tuning my new motor/carb. I was starting to get a bit more valve train noise and on my last couple of wot's, I noticed it didn't have as much power as it used to. Ran fine everywhere else though. That's when I pulled the pump and found the worn rod. Put in the one you sent me and ran it just a few miles before the valve train noise started getting worse. Pulled the valve covers and found issues that I posted another thread about. Still waiting on new lifters from Johnson, so unfortunately the motor is still sitting apart.
On another note, I still have the other 2 "nos" rods. If anyone has a way to test their hardness, I will drop them in the mail. I'm curious as to what they really are.

Did you happen to get those rods from Ehrenberg by chance?

 

[hunt2elk]

Did you happen to get those rods from Ehrenberg by chance?

No, I won't buy anything from that arrogant sob.

 

[440 Charger]

I saw another thread going about our fuel pump pushrods, and naturally there's folks responding with their own bad experiences and even some pictures of worn-down ends, but it got me thinking....

It just doesn't take a ton of force to move that fuel pump arm. You can hold a pump in one hand, and operate the lever with the other. In addition there's oil (presumably) getting to the ends. So while it very well could be just inferior metals, for something that *shouldn't* be seeing a lot of pressure even at it's max stroke, they sure seem to be causing all kinds of hell...
Are there other possibilities worth considering? Is there anything else that could wear them down like that?

Pump arm manufactured at a funky angle, or other pump defect that that puts excess pressure on the pushrod, like the arm bottoming out?
Eccentric lobe finished too rough? Or not ground correctly, putting excess pressure on the pushrod?
Installing them without assembly grease causing a bad wear situation from start-up, like we've seen with lifters and other parts?

Could be all the above but things now a days are junk,.

 

[440 Charger]

It's quite disturbing to me (on this subject at least) that even NOS isn't a "safe haven"...
because there's plenty of anecdotal evidence that the originals lasted a very long time.
That tells me the cams aren't what they used to be and apparently are quite a bit more abrasive, for whatever
reason.

The sad part we want these to run and last Just had me nephew over and he said first off I had no idea this car was this big lol.