Bent a push rod - Need advice

Humbucker · #1 (**permalink**) 03-25-2006, 09:52 PM

Darn it! A friend and I just installed new AFR 185 heads. I upgraded to new roller rockers, stud mounted, and hardened push rods. Engine is a 392 Ford Crate.

We got her fired up today, but she didn't run right from the get go. She stuttered and coughed a bit, and bucked going down the road even at 3000 rpm. He felt something was wrong with the fuel setup, but I suspected something bigger.

We pulled the plugs and noticed all indicated a very rich setting except for the #6. It looked fine. We pulled the valve covers and checked the feel on the pushrods as I cranked the engine around. The #6 intake was very tight. We removed the rocker and sure enough, the pushrod was bent. All the other rods were pulled and they look fine.

Any ideas on what might have caused this and what possible damage could have resulted? I fear what we might find... I'm assuming we tightened the rocker too much during the setup. Perhaps no oil was in the plunger when we set this one?

Any help would be MUCH appreciated.

undy · #2 (**permalink**) 03-26-2006, 05:33 AM

Replace the pushrod and readjust the valves. You need the run a compression check to make sure you don't also have a bent valve before you fire it up again. The valve "kissing" the piston could bend a pushrod. You definately don't need a valve head popping off going down the road..

392cobra · #3 (**permalink**) 03-26-2006, 06:12 AM

Jake,
Don't know if things have changed with the 392 Ford crate.I had one and had looked into putting the AFR 185 on it.
Found out that the valve reliefs would have to be flycut.

Humbucker · #4 (**permalink**) 03-26-2006, 06:13 AM

Quote:

Originally Posted by undy

Replace the pushrod and readjust the valves. You need the run a compression check to make sure you don't also have a bent valve before you fire it up again. The valve "kissing" the piston could bend a pushrod. You definately don't need a valve head popping off going down the road..

Would overtightening (even by only a turn) cause the valve to touch the piston? Also, why would the valve hit the piston on only one cylinder and not the others? I'm not doubting at all. I'm just trying to learn...

Thanks!

Humbucker · #5 (**permalink**) 03-26-2006, 06:26 AM

Quote:

Originally Posted by 392cobra

Jake,
Don't know if things have changed with the 392 Ford crate.I had one and had looked into putting the AFR 185 on it.
Found out that the valve reliefs would have to be flycut.

Hmmm... When I checked into it I found they should fit. There have been a couple articles (I'm sure you're aware) where they put the 185's directly onto the 392 stroker with no problems. When I called Ford Racing, they said the Z heads would bolt directly on with no problems. I figured since the intake and exaust valve size was the same it should be good to go. As well, I emailed Keith Craft with my exact engine year and model, and he too suggested the AFR heads. So based on those three things, I ordered them from Keith and away I went.

Knowing you probably did a bit of research too, I'd be VERY interested in finding what you learned. There certainly seems to be some kind of problem, and I certainly wouldn't rule out your theory at this point. If you get the chance, let me know.

Thanks for your time.

Jerry Clayton · #6 (**permalink**) 03-26-2006, 06:37 AM

Take a cylinder leakage test--if all is well there--

A common(sometimes,occasionally,seldom never)occurrance when two buddies are working on an engine, drinking beer, smoking cigars, farting and telling lies--you possibly could of had that pushrod setting on the edge of the lifter and bent the valve as you turned the engine over--if you bent the intake valve, that cylinder would foul the intake charge for the other cylinders and make them look rich

Jerry

392cobra · #7 (**permalink**) 03-26-2006, 07:17 AM

"I figured since the intake and exaust valve size was the same it should be good to go. "

That could be where the difference is.

I had the M--6007-D392 w/ GT-40 heads (M-6049-X303).These heads come with 1.94" intake and 1.54" exhaust.

The AFR185 is 2.02" and 1.60".

nevermind65 · #8 (**permalink**) 03-26-2006, 07:39 AM

Sounds to me like you just had the valve adjusted a bit too tight. I would guess that you bottomed the pushrod out in the lifter, and as soon as the lifter pumped a bit, the pushrod bent.

Especially if none of the other pushrods are bent.

Humbucker · #9 (**permalink**) 03-26-2006, 08:10 AM

Quote:

Originally Posted by 392cobra

"I figured since the intake and exaust valve size was the same it should be good to go. "

That could be where the difference is.

I had the M--6007-D392 w/ GT-40 heads (M-6049-X303).These heads come with 1.94" intake and 1.54" exhaust.

The AFR185 is 2.02" and 1.60".

I was referring to the intake and exaust for the "Z" heads that Ford said would bolt on no problem. They are 2.02 and 1.60.

Humbucker · #10 (**permalink**) 03-26-2006, 08:26 AM

Quote:

Originally Posted by Jerry Clayton

Take a cylinder leakage test--if all is well there--

A common(sometimes,occasionally,seldom never)occurrance when two buddies are working on an engine, drinking beer, smoking cigars, farting and telling lies--you possibly could of had that pushrod setting on the edge of the lifter and bent the valve as you turned the engine over--if you bent the intake valve, that cylinder would foul the intake charge for the other cylinders and make them look rich

Hahaha!! You described us to the tee. No beer, but everything else. Cigars and all.

Out of curiosity, wouldn't the bent pushrod also cause the same rich condition in the other cylinders?

Humbucker · #11 (**permalink**) 03-30-2006, 07:25 PM

bump if you love cobras!

Eljaro · #12 (**permalink**) 04-01-2006, 10:20 AM

I have experienced bent pushrods and just a week ago a broken pushrod.
This is like the pushrod looked when I took the valve cover off:

I run Dove aluminum rockers, and I have had to grind the area around the screw with the ball which takes the cup of the pushrod because the cup was touching the rocker and did probably hang inside and was pushed out of its location during one valve float event during my last racing.
Here you see a ground rocker:

Another area to check is the holes for the pushrods. Sometimes the pushrod touches or rubs inside the hole in the manifold; If you adjust the valve lash with a slightly bent pushrod it will force the cup sideways on the ball and eventually the cup will break. It happend to me once. I had to grind some holes in the manifold to make space for the pushrods. here an example:

Hope this helps

eljaro