Bent Pushrod

[Little Pete]

Trying to get this 65 Monaco on the road. Was cleaning up the valve covers and putting on new gaskets, low and behold a bent pushrod on the drivers side. 383 car, now the million dollar question......Why and what caused it. The car even ran decent before and now all of sudden...….bent pushrod. Why? Guess I'll be digging into it over the weekend. Low mileage car, OEM rockers (non-adjustable). Bolts seemed tight in the rocker arm assembly. Trying to avoid everything I can not to have to pull the head to investigate further. Maybe a stuck lifter, doubt I'm that lucky though.

New pushrods about $25-$35 dollars, but is that the answer? Just to chance bending another pushrod and be out the money.

Huge setback! Any good troubleshooting thoughts?

 

[C Body Bob]

Stuck valve can do that too

 

[Little Pete]

Stuck valve can do that too

Agreed. Just trying to avoid pulling the head.

 

[saforwardlook]

You must have run it on bad gas. The varnish in bad gas will coat the valve guides and eventually the valves will sieze up from the heat and build up of varnish and then the pushrod bends. It is the most common reason for this happening.

I have in some cases been able to free up the valve by spraying carb cleaner on the valve stem that is stuck (remove the rocker shafts and tap each valve with a hammer to see which one(s) are stuck and keep spraying and letting the stuck ones soak for a day or two). Often times you can get them freed up. And you must immediately change any fuel in the system to fresh fuel. You can not run a car on bad gas and expect it to not do this. You should be able to smell the fuel and tell it is bad.

 

[Little Pete]

You must have run it on bad gas. The varnish in bad gas will coat the valve guides and eventually the valves will sieze up and then the pushrod bends. It is the most common reason for this happening.

That's the most reasonable answer I could have ever expected. Ironically enough I just put in a new gas tank, lines, and rebuilt the carb because of bad gas and rust in the lines. Smelled like varnish. Makes perfect sense. Now what's the next step? Pull the heads and get a valve job I'm sure.

 

[Little Pete]

Though I've never seen one bent that bad without piston to valve contact?

Bad wrist pin or rod bearing?

 

[Davea Lux]

Might want to check the spurt hole in the rocker to be sure it is not plugged, if that valve was not oiling that can make the valve seize up. I would spin the rest of the push rods to be sure there are not any other bent ones. (You can also roll the push rods on a sheet of glass to check if they are bent). If this car sat for a long time, sometimes the valve gear can rust up and seize. Remove the rocker shafts as noted above as you will need to do that to replace the bent push rod anyway. You can usually free the valves up with some diesel in a squirt can applied to the stems, let it sit overnight. Penetrating oil will also work. Tap the valves with a brass drift and a hammer to be sure all move freely.

DAVE

 

[C Body Bob]

Put the push rod in a vise & straighten it back out. Reinstall it. Turn engine over with a breaker bar. Watch valve train movement. See what happens. Feel what happens. Tight spots etc

 

[Little Pete]

Might want to check the spurt hole in the rocker to be sure it is not plugged, if that valve was not oiling that can make the valve seize up. I would spin the rest of the push rods to be sure there are not any other bent ones. (You can also roll the push rods on a sheet of glass to check if they are bent). If this car sat for a long time, sometimes the valve gear can rust up and seize. Remove the rocker shafts as noted above as you will need to do that to replace the bent push rod anyway. You can usually free the valves up with some diesel in a squirt can applied to the stems, let it sit overnight. Penetrating oil will also work. Tap the valves with a brass drift and a hammer to be sure all move freely.

DAVE

Thanks Dave! I plan to give it my attention this weekend. I'll keep you updated. I was also thinking valve float? Though that pushrod is bent worse than I've ever seen. Seized valves are not a fun idea. Though I'm still worried about the bottom end also.

 

[Little Pete]

Put the push rod in a vise & straighten it back out. Reinstall it. Turn engine over with a breaker bar. Watch valve train movement. See what happens. Feel what happens. Tight spots etc

Thank You for the advice. Can't hurt to try. I'm also going to incorporate Dave's thoughts as well. See if I have a stuck valve. Lifters look good surprisingly .

 

[Yatzee]

Trying to get this 65 Monaco on the road. Was cleaning up the valve covers and putting on new gaskets, low and behold a bent pushrod on the drivers side. 383 car, now the million dollar question......Why and what caused it. The car even ran decent before and now all of sudden...….bent pushrod. Why? Guess I'll be digging into it over the weekend. Low mileage car, OEM rockers (non-adjustable). Bolts seemed tight in the rocker arm assembly. Trying to avoid everything I can not to have to pull the head to investigate further. Maybe a stuck lifter, doubt I'm that lucky though.

New pushrods about $25-$35 dollars, but is that the answer? Just to chance bending another pushrod and be out the money.

Huge setback! Any good troubleshooting thoughts?

View attachment 190151

It would appear as if the rod came out of the socket on the rocker but not the lifter socket and dead headed against something up top like the underside of the rocker close to the rocker shaft. Could be a frozen valve but you can verify that by prying down on the valve stem. Could be broken "stacked" spring coils or at worse a seriously bent valve stem. Only way to tell is to remove the intake and head because you make actually have had a piece of the engine casting break off in the valley area during or after this occurrence.

 

[Little Pete]

It would appear as if the rod came out of the socket on the rocker but not the lifter socket and dead headed against something up top like the underside of the rocker close to the rocker shaft. Could be a frozen valve but you can verify that by prying down on the valve stem. Could be broken "stacked" spring coils or at worse a seriously bent valve stem. Only way to tell is to remove the intake and head because you make actually have had a piece of the engine casting break off in the valley area during or after this occurrence.

Absolutely agreed! I'm going to start with the intake and valley pan first investigate a little then pull the head. You are 100% correct, I found the push rod just laying out of the rocker. I'll keep you updated.

 

[Little Pete]

It's also a factory A/C car and that should make everything that much more difficult.

 

[Davea Lux]

Absolutely agreed! I'm going to start with the intake and valley pan first investigate a little then pull the head. You are 100% correct, I found the push rod just laying out of the rocker. I'll keep you updated.

You might consider straigtening up the bent push rod and reinstalling so you can run a compression check on the engine. That will most likely tell you if there are any bent valves.
This would also be a good time to check your timing chain as a bad chain will cause the type of damage to push rods that you have.

Dave

 

[65Fury440]

If that engine sat for a long time at some point, and was then started with a sticky valve, you could get a bent pushrod like that.

Maybe also if the lifter was collapsed, then the motor started and revved right away, it may have hammered that pushrod.

I was taught to go through and smack the valves loose with a mallet on an engine that sat a long time.

Can you push down on the lifter to see if it is collapsed?

As was suggested, try to clean the valve stem with something. Maybe if don't have a valve spring compressor, you can pop the rocker shaft off, and go through and hit the valves, see how that one compares to the others, determine if it was a previous problem, or if it's a currently stuck valve.
I would run some MMO/ Trans fluid through that thing and try to un- varnish it.
That car had a dead hole for sure, shes gonna really run good hitting on all 8!

 

[PurpleBeeper]

These guys all have good points. For my 2-cents.... buy one lifter (smear with cam break in paste), one pushrod & one rocker arm. Install them. I like the idea of turning the motor over with a breaker bar & watching that valve. If all seems OK, fire it up. IF you timing chain is wearing out, you can usually see this by severely fluctuating timing with your timing light (it bounces all around). If it does that, put in a new timing chain. The posts above give good advice, but I'd rather not pull off a head either personally.

 

[imperigal]

Going through this same thing on the 73T&C right now. 2 bent rods and one just hanging out (lost contact with rocker arm). The spacers were worn out, causing a lot of slop at cylinders that had the bent rods. After a trip to Mancini Racing (stock parts....in stock!), the spacers, rocker arms and push rods going in this afternoon.

 

[Polara_500]

Going through this same thing on the 73T&C right now. 2 bent rods and one just hanging out (lost contact with rocker arm). The spacers were worn out, causing a lot of slop at cylinders that had the bent rods. After a trip to Mancini Racing (stock parts....in stock!), the spacers, rocker arms and push rods going in this afternoon.

View attachment 190428

That car is giving you quite a workout, isn't it?

 

[imperigal]

That car is giving you quite a workout, isn't it?

Oh, I know it could be SO MUCH worse! I'm actually quite enjoying it (aside from the PITA starter issue I had). Found that two valves were stuck/sticky. Penetrating oil applied. They were already loosening up. Will let sit for a while to make sure they free up all the way.

 

[Davea Lux]

These guys all have good points. For my 2-cents.... buy one lifter (smear with cam break in paste), one pushrod & one rocker arm. Install them. I like the idea of turning the motor over with a breaker bar & watching that valve. If all seems OK, fire it up. IF you timing chain is wearing out, you can usually see this by severely fluctuating timing with your timing light (it bounces all around). If it does that, put in a new timing chain. The posts above give good advice, but I'd rather not pull off a head either personally.

Putting a new lifter on a well worn cam will usually make the cam lobe go flat. I would do this only as a last result if the original lifter was dead. Figure on putting a camshaft in the car in about 20k or less.

While the breaker bar is on the is on the crank pulley, remove the distributor cap and line up the timing mark to TDC. Now rotate the crank shaft back and forth, it you get 12-15 degrees of free play before the distributor starts to move, the chain is out of spec and needs to be replaced. If you get 20 degrees or more free play, the chain is at the point of failure.

Dave