15th ANNI T/A

Hi guys, Newbie here but long time lurker

As the title says I am having trouble with the exhaust rocker on cylinder #3 falling off the valve stem and bending push rods.

This motor has approximately 12500mi since it was rebuilt. The car it is in was my daily driver for close to a year and it had no valve train issuses. I was driving it home one day and I heard a popping sound from the carb and what felt almost like back firing. I got it home checked the carb it looked fine. Took off the valve covers and I found cylinder #3's exhaust rocker rotated clockwise off the valve stem and the matching push rod was bent. I replaced the push rod reset the valve lash (tighten until push rod stops rotating plus 3/4 turn). I fired the car up and it had no valve tick and all the cylinders were firing as per normal. I drove it a half mile from the house and the same popping sound comes back. At home I pull the valve cover same issue bent push rod with rocker rotated off the valve stem.

I will post pictures tonight when I get home of the current state of the rod, rocker and valve stem.

I was wondering if anyone has had this happen to them before and If anyone here has any idea what would be causing this??

Engine Specs:
I am running the stock stamped rockers (most likely used), no guide plates, factory push rods and factory iron heads. (Pre 87). The motor has a sealed power cam and lifters in it but it is very mild and i have no idea what springs were used the engine builder never told me.

Thanks in advance!
Marc

Bob88GTA

iTrader: (2)

Welcome to the site. The problem may be a collapsed lifter. If so then you need to remove the intake to replace it. Do you know if the push rods were changed and replaced rocker arms? Check the valve spring too. I could be broken.
Do you have an adjustment procedure for setting the rocker arms?

15th ANNI T/A

Thanks for the quick reply,

I am leaning towards the bad lifter idea because the spring looks fine. The rockers and push rods may have been changed but I doubt it.

The engine builder I used at first seamed really reputable and he did know his stuff. He just cheaped out on parts and didn't put much care into the build. The current cam is the second cam I have had in the motor since the rebuild. The first one flattened a lobe during break in because he didn't put assembly lube on one lobe, which lobe I forget. That cam was replaced with another sealed power cam and lifters he gave me under warranty.

I have never used sealed power but I found the warranty cam and lifters he gave me back then on summit for approx $40. the equivalent Edelbrock cam was almost $130. So I'm hoping it is just a cheap set of lifters and one just decided to kick the bucket.

sofakingdom

iTrader: (1)

Probably nothing wrong with either the spring or the lifter. Especially not "collapsed", whatever that would be, if it existed.

More likely, something to do with the push rod guide hole in the head, the rocker arm itself, or the guide plate. Which one would depend on what system you're using to locate the rocker. Most likely, from your description of the heads, your motor uses the holes, and that one guide hole is wallowed out.

15th ANNI T/A

OK, so I had a chance last night to check out the situation a little and take some pictures of the aftermath.

I first started by grabbing each rocker and trying to rotate it the same way the one that fell of did with varying results. some would move side to side and others were very tight with no movement what so ever. it was also random the rockers movement had no relationship to the position of the lifter.

I have discarded the possibility of it being the lifter or the cam lobe because the lifter is up and doesn't move down. I am saying that while making the assumption that the lifter isn't seized in its bore. I didn't have enough time to take everything apart.

In your opinion what do you think would be the best way to solve this issue. Would it be installing new studs and guide plates or could I try using self aligning rockers? I know self aligning rockers are for 87 plus motors but if the alignment tabs clear my spring retainers it would be way easier to fix.

Would any one be able to give me an approximate depth of the alignment tabs on a set of those rockers? I would be super grateful

TTOP350

iTrader: (8)

Check the rocker arm studs as well, maybe one is slowly pulling itself out of the head.

RBob

iTrader: (1)

The keepers and retainer isn't installed properly on that spring. It is possible that the retainer is smacking the top of the valve guide causing the push-rod to bend. If anything the spring pressure is going to be higher then normal.

RBob.

15th ANNI T/A

Ya I noticed that too.

I have decided i'm going to take this opportunity to refresh as much of the motor as I can myself because I'm already half way inside this motor. I'm going to install a new cam that was meant for another project which I no longer own (an Edelbrock 2102 I believe), replace all the lifters, push rods and rockers and valve springs. Like this I can use up some of my spares lying around and I know what I have is good and then I can work from there.

I am also going to check the heights of all the rocker studs. TTOP350. I didn't even think of that.

Thanks to everyone so far for all the suggestions!

-=Z28=-

iTrader: (3)

Make sure you have the correct length push rods too. That valve needs to be refaced.

Yes, those keepers look like they arnt seated correctly. Also in the one pic, the push rod is in the wrong position on the lifter as well. When adjusting rockers, kinda let them lay the way the they want to. Not always perfectly in line with valves. Just make sure they push evenly on the valve.

Maybe leave the cover off and run it and see what happens.

to test those keepers when you think they are in place, take a small plastic hammer and tap on the top of all valves. you will know if one isnt right.

TallTim

iTrader: (2)

Maybe the rocker arm nut backed off? I had that happen with nuts that lost their tightness. They say if you hammer them just right (off the car!) they regain their tightness but too much and it will lock itself to the stud and then you have to replace both :-(

sofakingdom

iTrader: (1)

I don't see anything wrong with the keepers; looks to me like the valve stem tip is completely wasted though, that head needs a new valve.


Put a straight push rod in there and take the same 3 pics, plus one perpendicular to the spring, showing the rocker tip sitting on the valve.

RBob

iTrader: (1)

Look at how much of the keepers are showing versus the valve to the right of it. Can also see where the rocker was pushing on the retainer (on the left). Which may be the reason the keepers are not properly in place.

RBob.

sofakingdom

iTrader: (1)

Mostly I see a valve stem with its tip ground off; and a retainer that has a mark where the bent push rod sent the rocker off to the side to beat on it.


It's all pretty messed up, but the keepers are not "out of place". They're right there in their groove where they belong.


It's not impossible that the spring is incorrectly shimmed, resulting in coil bind; and that's the root of the problem. Hard to tell about that from the pics though.

-=Z28=-

iTrader: (3)

Usually those green keepers are a std. Pretty sure you can go up to .060 either way to get correct install height. Someone has rebuilt those heads for sure so who knows whats up...

tealman92

I bet you have a bent valve and its no longer returning all the way to the seated position causing the rocker to come off and during the rocker comming off the pushrod is now bouncing around and bends during the process

15th ANNI T/A

Thanks for the info guys!

I decided to take advantage of the long weekend here in Ontario Canada to see exactly what was going on with this. I pulled the fallen off rocker and the one next to it just to compare to see what damage had been done. When I did that I think I found out why the rocker was continuously falling off. The rocker stud itself had a cut in it that almost half way into the stud and about 0.090" wide. I know a rocker cutting into a stud is a symptom of a loose rocker. So I checked the rocker and saw no damage or scribe marks from metal on metal contact. I'm thinking that the guy I had rebuild my engine didn't notice or care enough to replace the stud. I rolled it on

I was lucky I had a spare parts 305 which I was able to remove a stud by stacking old rocker pivot ***** with washers and slowly tightening a nut on the stud. I took my time and used lots of lube. I did the same on the cut stud except even more carefully so it wouldn't snap off. I was able to hammer in the new stud (took a lot of force). So I wouldn't destroy the top of the stud. I threaded an old lock nut on to it and pounded that. the nut was toast but my new stud is good to go. I used my vernier to set the depth as my heads had a through hole for the studs.

I'm hoping replacing this stud fixes my issue. I'm going to clean up the valve stem and reinstall everything. I have decided not to put any more money into this motor and save all the new parts I bought for later. Currently I have #333882 heads which I have heard are the best of the worst heads. So I don't want to put money into these. I would rather put that money towards new better flowing heads.

Thanks again I should fire it next weekend so I will keep everyone posted.