Amazon: Bent Push Rod

[ColoradoAmazon]

I purchased a 1962 121 that came with a rebuilt B18 engine. The previous owner installed the engine but never completed the installation or ever fired the engine.

I have completed the installation and have run the engine. The engine initially ran fine but started running rough. I discovered cylinder #1 had no spark and was really low on compression. I removed the valve cover and discovered the intake push rod on cylinder #1 was bend and is stuck in the head.

I'm a novice when it comes to engines so I'm looking for some input.

1 - How does something like this happen? (wondering if the valves were not adjusted properly. Some of the other push rods are loose)?
2 - I'm thinking I need to remove the rocker shaft, pull out the bent push rod, install a new push rod and adjust the valves.

Any input on what caused this and how to remedy would be greatly appreciated. Thank You!

[Juular]

Fairly certain this was caused by the clearance adjustment being in completely the wrong postcode. Too loose and the pushrod will jump out of the rocker assembly and possibly bend on the next cycle. Too tight and the forces in the valve train could bend it.

Nothing to lose by replacing that pushrod, maybe all of them (check for staightness) and redoing the clearances.

[Rustinmotion]

Bent pushrod could be a stuck valve or interference with valve and piston , binding springs or a sticking rocker arm, was the engine tuned? High lift cam or skimmed head?

[ColoradoAmazon]

I did not adjust the valves and just assumed they were adjusted properly. Definitely a mistake. I do not think they are adjusted correctly. Hopefully nothing other than the push rod/rods are damaged.

This is what information I have on the engine rebuild: "Rebuilt B18 bored out to a B20, B20 head shaved 2mm with a K cam". However I cannot confirm if any of this is true. I'm going by what's on an order form for some Mikuni carburetors and the previous owner's recollection. The engine builder passed away.

I'm going to remove the push rods and check them for straightness, buy some replacement push rods, replace the push rods, adjust the valves and check everything.

Off to watch some YouTube videos. Anything I should look out for?

[Rustinmotion]

Originally Posted by ColoradoAmazon

I purchased a 1962 121 that came with a rebuilt B18 engine. The previous owner installed the engine but never completed the installation or ever fired the engine.

I have completed the installation and have run the engine. The engine initially ran fine but started running rough. I discovered cylinder #1 had no spark and was really low on compression. I removed the valve cover and discovered the intake push rod on cylinder #1 was bend and is stuck in the head.

I'm a novice when it comes to engines so I'm looking for some input.

1 - How does something like this happen? (wondering if the valves were not adjusted properly. Some of the other push rods are loose)?
2 - I'm thinking I need to remove the rocker shaft, pull out the bent push rod, install a new push rod and adjust the valves.

Any input on what caused this and how to remedy would be greatly appreciated. Thank You!

Originally Posted by ColoradoAmazon

I did not adjust the valves and just assumed they were adjusted properly. Definitely a mistake. I do not think they are adjusted correctly. Hopefully nothing other than the push rod/rods are damaged.

This is what information I have on the engine rebuild: "Rebuilt B18 bored out to a B20, B20 head shaved 2mm with a K cam". However I cannot confirm if any of this is true. I'm going by what's on an order form for some Mikuni carburetors and the previous owner's recollection. The engine builder passed away.

I'm going to remove the push rods and check them for straightness, buy some replacement push rods, replace the push rods, adjust the valves and check everything.

Off to watch some YouTube videos. Anything I should look out for?

Check for spring binding, if the PO used updated valve springs without machining the spring pockets you could be binding up the springs once it’s back together hand rotate the engine and make sure at full open there is still a gap between each of the spring coils

[Derek UK]

Not the first time there has been a bent pushrod like this and it won't be the last. Roll pushrods on a sheet of glass. A mirror works fine. This may be the only one that needs replacing.
Be aware that some B18 blocks don't take to be being bored to B20 size due to core shifts when they were made. Can make the bore walls very thin and prone to cracking. If a good engine builder is aware of this the block can be checked before and after the rebore. Good luck.
Not sure what CR is now with a 2mm skim but best to user the highest octane gas you can.

[Ron Kwas]

CA;

The engine will likely have survived this issue if it happened on initial startup, and if corrected immediately, but you may consider engaging the help and oversight of an experienced "Engine Elmer"...because this sounds like a fundamental error to me, which an experienced guy would have avoided...

To add to info from others...(...been traveling so just catching up)...the significant forces necessary to bend a Pushrod can only be generated when something in the Valvetrain is not completely free to move as it should...and for a brand new (what I would consider to be a significantly modified engine), turning the Crankshaft manually through a few turns during valve adjustment, and BEFORE initial Startup to assure this, would have shown a stacked and binding Valvespring, or stuck Valve.

It sounds like the Valvetrain was anything but correctly adjusted "Some of the other push rods are loose"...the Valvetrain MUST be correctly adjusted before even thinking of starting!!! NO PRESUMPTIONS!

I'd advise you do some manual crankshaft rotations after replacing the bent Pushrod...paying particular attention to the Valvetrain including Valve clearance and adjustment on every single one at TDC for every single piston, NO EXCEPTIONS!)...all eight are essentially similar in action and clearance, so the situation that happened to one, might be in place on others...! Triple check everything and assure it is right, before attempting another startup!

Good Hunting!