Dang it!

[Lefty71]

Why is my Imp eating fuel pump pushrods??

I'd be looking carefully for a potential oil splash problem, or lack thereof. Sounds kinda off-the-wall, but could some variance from stock cause the lobe to miss out on the needed oil in that particular spot?? Who remembers what the back of the original cam sprocket looks like, any grooves?? And, along those lines, wasn't there someone (not here) recommending a tiny pinhole in one of the 3/8" oil galley plugs for Torrington or bronze bush sprocket oiling?? Might have even been a chebbie solution, but it might just help you with this one. HTH, Lefty71 (from outta left field on this one).

 

[Ripinator]

Never seems to get any longer. "I measured it three times, still short"

Time for a new cam, put a big lumpy stick in there this time. @Ripinator

Make it cackle. . .

 

[bluefury361]

Matt. The only reliable Mopar push rod is a NOS, (original), from back in the day. Mopar Performance had them remanufactured sometime in the 80's/90's and using one of them will result in the issue your having. I would find either a NOS rod or use a original used one showing no wear.

 

[70bigblockdodge]

I have to say after wipping 2 on the same cam I would really be looking at a new cam or electric fuel pump.

 

[commando1]

It's a simple rod.
I wonder if one can be machined out of titanium.
Yah, might be a bit pricey, but...

 

[detmatt]

Thanks for the input gents. I think this is the way to go as far as replacement.
Hughes Engines
Thank you @Clover for this recommendation.
I think I did mention that I added an electric pump a couple of years back.
Is the cam lobe wiped? Not completely I know that for sure. I pulled the distributor for a visual inspection from the top and also turned the engine over by hand with my last good(or at least full length) oem pushrod in place and with a finger on it and there was absolutely travel on it. I put it back together with some assembly lube on it and I’m going to run with it like that.
I’m not putting another cam in it until the bottom end finally needs to be rebuilt.

 

[bajajoaquin]

I think you've moved on, but let me get this straight:

Original cam and pushrod.
Replaced the original cam, kept the original pushrod
Found that the original pushrod wore down
Replaced with new pushrod, same cam
Replacement pushrod is now worn

Was there any indication that the pushrod was worn down when you had the original cam in it? Were you getting any of the lean stumbles or stalling? If not, I'd venture to say the manufacturing error is on the replacement cam. I think you went with a MP 440/375 cam, right? That would imply that it's just as likely (or unlikely) to have a manufacturing error as the NOS pushrod you found.

Just talking this through, not trying to tell you anything you don't know....

When you replace a cam, you're supposed to replace the lifters, and treat them like a set. I've never before heard that you should consider the pushrod to be part of that replacement set. I'd infer that the fuel pump has a much lower spring pressure than valve springs, so the wear is typically much less. Again, that suggests the issue is with the new cam rather than the original pushrod.

At least, is suggests it to me

 

[detmatt]

The pushrod that was in it when I got the car was well on its way to worn out before I replaced the cam. The very drivability issues that were symptomatic were one of the deciding factors in rebuilding the top end.

 

[bajajoaquin]

Well, there goes that theory.

When you posted about it previously, I had mentioned that I'd be curious to know what the composition of the rod is, or what the specs are for them. It shouldn't be too hard to harden and temper a pushrod if necessary. I noticed that the Mancini pushrod listed the hardness at Rc30. If stock is Rc15 (as noted), that's a big difference.

 

[mr. fix it]

It's all my fault. I'm the one who mentioned it earlier today. I cursed it.

glad to see you're stepping up and admitting it Stan
Now for your next prediction?
Just don't tell us that the value of our beloved C bodies is about to tank!

 

[commando1]

I noticed that the Mancini pushrod listed the hardness at Rc30. If stock is Rc15 (as noted), that's a big difference.

I think (emphasis on "think") mopar cams of that era were around Rc30
and new aftermarket cams are as high as Rc60.
Which item is going to be considered the sacrificial metal if the lube is not up to the task.