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Classic Mustangs Tech Forum

Technical discussions specific to 1964-1967, 1968-1970, and 1971-1973 Classic Mustang. Discuss all tech related to in-line six cylinder and V8 powered Vintage Mustangs here.

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Unread 07-25-2011   #1 (permalink)
OKP
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Default Bent push rods, what's the cause?

The 289 engine of my 67 coupe was not running nice at all when I bought it, so I decided to troubleshoot. I knew it needed a new gas tank and a carb rebuild. I did all that and replaced all like sparkplugs etc etc.

Then I took off the valve covers and I saw that 4 rockers were off the pushrods. After further inspection, I saw that 4 pushrods were bent of which 2 seriously. I had to take off the intake manifold to get the 2 worst bent push rods out. See pictures. Tonight I saw the stud rocker arm of several cilinders had a difference in heigt. So I could never get the rockers properly installed on the studs, too much gap between the rocker and the spring. Ho can I get this problem fixed and what could be the cause of the bent pushrods? I don't want to install just new pushroads with the risk that it happens again.

Thx for any advice,

Eric
Antwerp, Belgium
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Bent push rods, what's the cause?-dsc06953l.jpg  Bent push rods, what's the cause?-dsc06955q.jpg  
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Unread 07-25-2011   #2 (permalink)
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Yep, studs are pulled. That'll do it. Best bet would be replace with screw in studs.
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Unread 07-25-2011   #3 (permalink)
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Pulled studs, I agree with explorer
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Unread 07-25-2011   #4 (permalink)
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factory rocker studs are only pressed in, the ones that are higher have been pulled out by the valve spring pressure.
like the other guys said, if you can pull the heads, take them to a machine shop and have them drill and tap the heads for screw in rocker studs.
shouldnt cost too much
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Unread 07-26-2011   #5 (permalink)
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That's what I though as well, thx for the confirmation.
I'll take the heads to a machine shop.

Eric
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Unread 07-26-2011   #6 (permalink)
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Default Bent push rods, what's the cause?

Hello Eric,
The answers you have gotten are 100% correct and will help you.
Having the heads worked on will cure the issue

BUT - I offer one small option and a little more info.

It seems as though this motor has been sitting and you have stuck
valves. As mentioned the studs have pulled up BUt they did that for a reason.

There is one thing you could try before pulling the heads.
Soak the valves with Marvel Mystery Oil.

With the valve covers off - - take some MMO and squirt is all around the valves and valve springs. Let it soak overnight - then repeat the process of spraying
with MMO.

Let this work for about 2 days. You can re-seat the valve stems. As the guys mentioned - they are pressed in BUT they can be re-pressed and MAY hold.

I only mention this becuase money is an issue for a lot of people.
The guys are right in saying to have the heads worked on - -BUT I have pressed the
studs back and had it work for years.

The process of pressing the studs back in is pretty simple. You take 3 nuts the size of the threaded part of the stud. Install the 3 nuts so that the top nut is hanging over he top of the stud. So the top nut is only on 1/2 way. Lock the nuts together using 2 wrenches. Then hit the top nut with a hammer. It will take a pretty good couple of whacks. You MUST be carefull not to hit the other studs. You will drive the stud back in and it should stay in the correct position.

THIS is by NO means the best way to fix this. It is an option if $$$ are tight. It will work BUT can't say the stud will not pull out BUT you have a great chance that they won't.

The other part of the problem is being certain the vlaves are free. To be certain - -you have to have the valves free or other issues will happen. The Marvel Mystery Oil will likely free the valves BUT there could be deposits on the valves in the seat area. I can expalin how to check the valve movement if needed.

For now - -I just offer a little info and an option.
I wanted you to know that the reason the studs pulled is the valves were stuck.

Let us know how you make out and if you want any more info on freeing the valves.

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Unread 07-26-2011   #7 (permalink)
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just a thought, you never specified wether the car is manual or automatic, so... at my High School we run 302's in our destruction derby cars with locked up C4's. To the point, we had a new driver and he decided to floor the gas on rev the s**t out of the motor. Well the is exactly what the valve train looked like, we had studs completely pulled out of the heads and pushrods that looked like spahgetti. I was amazed the bottom end held together. So others can chime in but that motor may have been over reved a time or two in the past.
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Unread 07-26-2011   #8 (permalink)
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thanks for all your comments. Tonight I am going to take off the heads to check if nothing is damaged. Anyway , I can buy as well a coupe of remanufactured heads from a fellow club member for not too much. I have to consider this.
thx anyway.

Eric
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Unread 07-26-2011   #9 (permalink)
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Without knowing the history on engine it's hard to tell. It looks clean from what I can see, a high lift cam, stronger springs and the high rev mentioned could have contributed to the failure.
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Unread 11-15-2011   #10 (permalink)
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I probably found the cause of the bent push rods. I took off the heads and 4 valves were stucked in the head because they were full of dirt (black carbon debrief). I removed all of the components of the heads, cleaned them properly and installed all new valves (in the proper way).
I installed as well a new timing chain and set it correct with the marks at TDC.

I have almost finnished rebuilding the engine, new head gaskets, etc. etc. I hope to fire it up this week. I'll let you know how it goes.

Eric
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Unread 11-15-2011   #11 (permalink)
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Default Bent push rods, what's the cause?

Hello Eric,
Always great to hear a follow up and let us know what is happening.

Take your time with the re-assembly and you should be fine.

Double check and triple check everything before the initial start.

Sounds like you are almost there

Thanks once again for the update

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Unread 11-16-2011   #12 (permalink)
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The timing marks should be 6:00 position on the camshaft and 12:00 position on the crankshaft, I've never paid attention if it is at TDC. Also if you installed new valves did you have the seats and valves reground, or at least checked how they are seating, or lapped the valves in the seats? Good Luck.
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Unread 11-18-2011   #13 (permalink)
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Quote:
Originally Posted by rex1965 View Post
The timing marks should be 6:00 position on the camshaft and 12:00 position on the crankshaft, I've never paid attention if it is at TDC. Also if you installed new valves did you have the seats and valves reground, or at least checked how they are seating, or lapped the valves in the seats? Good Luck.
Timing marks are OK, and yes when I put in the new valves I grinded them with special paste so they have an optimal fit.
I only have to attach the exhaust now to the manifolds en recheck all the wiring. I hope to fire it up this weekend.

Eric
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Unread 11-18-2011   #14 (permalink)
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OKP, You mentioned that you have installed new valves. A question that I have is this. Did you do anything to the valve seats in the cylinder heads? Did you just install the new valves and use the special paste (Lapping Compound) to lap the valve to the seat? If this is the case, you need to look at where the grinding (Lapping) marks are located. The grinding marks need to be located in the center of the valve seat area on both the valve and the seat located in the cylinder head. If the seats are not sealing properly, there is a chance of having a burned valve. Check this closely.
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Unread 11-19-2011   #15 (permalink)
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Quote:
Originally Posted by OKP View Post
I probably found the cause of the bent push rods. I took off the heads and 4 valves were stucked in the head
If Print Dad says it, then it is almost always so.
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