I don’t really get this, but just my luck I guess. The past year I went through a 71 440 HP motor. Had broken valve spring, which snowballed into me pulling engine and going through pretty much everything. New bearings, cam, valve job etc. I reused the fuel pump pushrod that was in there already and probably from the rebuild prior to my Dad purchasing in 1990, so assuming it was done in the 1980s. I didn’t actually measure the pushrod when assembling, just looked it over and it “appeared” fine (wish I did now). Some tiny wear marks on ends and I put the cleanest looking end towards the cam. New, not vintage era, Carter 3/8” inlet fuel pump.
Fast forward a few hundred miles on the motor and I noticed fuel starvation at high RPMs and engine stalled a couple times on uphill climbs. Would restart until it didn’t. Figured it was the pump and upon removal along with pushrod, see the pushrod is worn down a good 3/8”. Lovely.

What I don’t get is this is the same pushrod from 1980 something, which I figured was from the era before all the issues. Was I just unlucky and put the side towards the cam that wasn’t hardened properly or could there be something else contributing? I cant find a spec, but the spring pressure on this pump appears to be ok. I can’t really compress easily by palm of hand, but compresses pushing against a hard surface. Doesn’t seem excessive or binding. Cam looks like it survived, don’t see any scratches or anything after going around full circle. I run Mobil 1, but use 2 bottles of ZDDP+ additive due to the 7 qt pan. I did use break in oil and ZDDP additive as well during break in.

Only thing I did different on this assembly was I used engine assembly lube on the pushrod and not my normal glob of grease. Is it possible that the assembly lube was too restrictive in the block bore and bound the rod during the critical break in period?

I am kind of lost on this for cause. I bought a new pushrod from 440 source, which I have used same in my last BB build that was missing an existing part, with no issues. That one I did use regular grease on assembly out of habit. I got a magnetic drain plug and plan to cut open filter to see how much was caught so far.