Bent same pushrod twice

[williamsGN]

Bent the #1 cylinder intake? pushrod this spring, Second pushrod inboard from the front. Replaced the rod, lifter and all new valve springs. Broke in the new lifter with some ARP lube and a summer of driving. This fall, first time leaning into it I bent the same rod. Camshaft looks fine, car misfired when I heard the ticking start, not sure if the tick or the misfire came first. Could I have gotten a bad Melling lifter from AZ or what else should I look at. TIA

 

[TIMINATOR]

When you changed the springs did you check the installed height and spring solid height on EVERY spring in reference to the cam lift? Did you also check the retainer to stem seal dimension with reference to the cam lift? Have you changed the cam or rocker ratio since all of this was checked? Other than a tight guide randomly seizing to the valve, that's about all I can think of.
TIMINATOR

 

[williamsGN]

When you changed the springs did you check the installed height and spring solid height on EVERY spring in reference to the cam lift? Did you also check the retainer to stem seal dimension with reference to the cam lift? Have you changed the cam or rocker ratio since all of this was checked? Other than a tight guide randomly seizing to the valve, that's about all I can think of.
TIMINATOR

Not familiar with spring height measuring in relation to cam, etc. Cam has been in the car for 15k, no issues till I bent the rod in the spring. Since Ive owned the car and driven it for 20 years with the same springs and no idea if they are originals, I decided to replace with Comp Cam 980-12 which I hear are a good stock replacement. I'm thinking the misfire might have hurt it, possibly the new lifter failed. Car has new plugs, wires, coil. I had it cutting out sometime ago, but has been pretty good since all the new ignition parts.

The rod and lifter were Melling parts, I thought that was a decent brand. maybe the issue lies there ?

 

[BRAD_PADGETT]

" I decided to replace with Comp Cam 980-12 which I hear are a good stock replacement." This was a mistake. These springs wear out quickly just like the original Buick springs, The correct springs for a stock motor are Comp Cams 981-16. This way you eliminate floating valves on a stocl motor.

 

[TIMINATOR]

How many total miles on motor?
What cam?
Was the cam and springs in there when you bought the car?
Did you just match up the pushrods, or verify that the bent one and new one was the correct length?
Did you "pump up" the new lifter full of oil when you replaced it?

 

[williamsGN]

" I decided to replace with Comp Cam 980-12 which I hear are a good stock replacement." This was a mistake. These springs wear out quickly just like the original Buick springs, The correct springs for a stock motor are Comp Cams 981-16. This way you eliminate floating valves on a stocl motor.

980-12 are the same number full throttle sells as a direct stock replacement.

 

[BRAD_PADGETT]

980-12 are the same number full throttle sells as a direct stock replacement.

I know. They are too weak.

 

[XracerX]

I know. They are too weak.

Not to weak if you shim them with a 0.030 shim compressing them down to 1.697" which will get you back up closer to the actual rated seat pressure of 92 lbs @1.7".

 

[TIMINATOR]

The problem? With 980 Comp springs is they are a high quality copy of the old Chevy Z-28 spring.
But knockoff Chairman mao copies sell for about a dollar to $1.25 each!
Real Comps are MUCH more!
They are bootlegged EVERYWHERE for a lot more as authentic Comp. parts.
Many "reliable" dealers/sellers unknowingly sell the cheap stuff in real or copied knockoff Comp apparent packaging.
The Comp 981s are a better choice, but only if purchased from a reliable source. I have seen junk in real and knock off Comp boxes come from Evil bay and You-know-who-zon sellers.
The reputable machine shops destroy the Comp and other packaging, others sell the boxes!
TIMINATOR

 

[John Larkin]

I would be more inclined to suspect a bent rocker arm from the original incident that allowed the push rod to get off kilter and be damaged. It would be hard to imagine spring bind on a stock valvetrain with stock replacement springs.

 

[TIMINATOR]

Net build lash engines (non adjustable valvetrain) have several different length pushrods available. Was the correct length one supplied and installed? As a retired engine builder, I have seen the wrong parts supplied often, not just with Buicks, but with other brands too. There are several different versions of "knockoff" springs out there too. Different length and pressures too, but unless inspected next to another, they may look the same.
If you are in there to replace a "bad" part, find the cause for the repeated failure, don't just replace the part, or you may be doing the job again. You are at the mercy (knowlege, or lack of it) of everyone that worked on it first. You have to remove the rocker shaft, so why not dissemble it and look for more problems. Same with pushrods, see if they are the same length, and compare that to the correct length, really look at the springs too!
If you didn't find what caused the (repeated) problem, you are doomed to repeat it. A lifter going bad may occasionally "pump up", that too can bend a pushrod if the retainer to seal distance is short.
My point is; don't just fix the symptom, find the cause.
TIMINATOR