I've only ever bent one pushrod in the years i've been racing the A-series.

The cause - dunno, just put it down to high revs.

Just for interest sake, it's very easy to change a push rod quickly if needed in an A-series...

Loosen your rocker adjuster right off, slide the rocker along the shaft against the spring, remove bent pushrod, put in new pushrod, let rocker go back to position, adjust clearance, off you go.

Like I say, had to do it once in a 20 minute service, job took less than 10 minutes.

This is why I will never use the aluminium rocker spacers you can buy, turns a simple job into a very lengthy one.

I would be checking coil bind myself. Without knowing even the lift of the cam, revving past 8K is always going to help pinpoint weaknesses in the valve train.

A long shot may also be valve float allowing the pushrod to become unseated, but with double valve springs this would be pretty unlikely.

Mystery camshaft, but the bent pushrod is a mystery... Even if the cam is a mystery, you should Always at least know the lift of it. There is a chance that that has been close to coil bind for a while and a rev to 8K with a flutter of valve bounce can cause terrible things indeed. Know your engine.

I think mattkb110 might be on the money especially so as it sounds like the previous owner had a mystery cam installed?, otherwise;

A15s naturally have a longer, thus weaker pushrod. I would be checking your oil supply to the rocker assembly which might have starved the rocker arms of lubrication making them bind into the rocker shaft and cease up. Sometimes they cease themselves so hard into the shaft that the don't even move.

Remove the rocker assembly and check all rockers are moving freely.

Also check your oil supply and pressure, I believe the previous recipient of the oil circuit is the cam assembly so be sure to check for pressure drop there as well.

I have heard of a very heavily sprung valve having enough pressure to bend the longer, weaker a15 pushrods, but that is most likely too much spring pressure.

While you've got it apart check all the clearances between the underside of the valve spring retainer and the top of the guide or stem seal. With a larger cam plus the head has probably been recoed at some stage (varying length of guides), things could be getting close under there.

The only time I've ever bent an A series push rod is through complete user error ie putting a motor back together in a hurry and not backing off all the tappets before turning it over. My fault not the Datsun's.

Long time no hear gino120y lol. Great to see you out enjoying that thing. Will have to share with an update of new car upgrades

Over reving could cause some damage but double valve springs usually good for over 8k.
I'd consider faulty rid or clearances. It wouldn't be seated if it were bent from my understanding
But wait for an expet to answer

as far as i know, one possible cause for bent pushrod is incorrect valve clearance.

Hi Guys,

I took my 120y for a track day at sandown on the weekend and bent an push rod for the third cylinder intake side!

Just need some help diagnosing the cause, what should be looking for and that will i need to take apart and check to ensure no other damage was done?

Info: A15 engine with a previously rebuilt oval port head running higher compression(?), double valve springs, lightened tomei pushrods and the bottom end has a unknown reground cam profile (the guy i brought it off lost the specs on it but i'd consider it a fast road cam profile)

I've never had any problems with the engine and it had been running well all day, no noises and really started to free up a bit after not been driven hard for a while, second last session of the day and just started the cool down lap when i noticed the engine missing and lacking power. Not sure at what point it actually bent?

Not sure if reving it out to far has caused it to bend but it didn't valve bounce so not sure, I had it out to a bit past 8k which i haven't done before but it seemed fine, could it just be a dodgy pushrod?
or does the fact that when i stopped & checked the rocker wasn't seated in the top of push rod, does this point to anything?

I'll put photo's up tomorrow when i get home from work, until then any idea's would be much appreciated.

Cheers