Broken Rocker Arms

Broken Rocker Arms

Joined: June 3rd, 2008, 8:07 pm

April 28th, 2012, 7:29 pm #1

Hi cleveland guys, I have 24 miles on the new engine, all low RPM below 3K. 351C with 408 SCAT kit. CHI 4V heads came assembled. What would cause this? Roller cam from MME. All of the rocker arms have stress webs on them. 4 have busted. Rods are straight. Where do I begin to figure out how to avoid this in the future? The car is at the shop, I will have to see what length the push rods are. Rockers are those Comp Ultra Gold 19045-16. In the close up shot, you can see where some of the gold got rubbed off....don't know it that helps to figure out what went wrong. The rockers on the other side of the block are in 1 piece, but again have the stress webs in the finish.

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Joined: December 16th, 2003, 1:59 am

April 28th, 2012, 8:02 pm #2

does the pushrod end of the slot show any evidence of contacting the poly lock?

and how much clearance is there on the valve end of the slot with the lifter on the cam base circle(no lift)

did you run a valve tip pattern at all?

there'll be phantoms, there'll be fires on the road... and the white man dancing
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Joined: March 12th, 2002, 2:39 pm

April 28th, 2012, 8:25 pm #3

Looks like the push rods are contacting the rocker arms at full lift. That is what is causing the anodizing to be rubbed off the rocker. Check the push rod in that area for signs of contact. Your geometry is off.
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Joined: September 6th, 2010, 5:18 pm

April 28th, 2012, 10:06 pm #4

Hi cleveland guys, I have 24 miles on the new engine, all low RPM below 3K. 351C with 408 SCAT kit. CHI 4V heads came assembled. What would cause this? Roller cam from MME. All of the rocker arms have stress webs on them. 4 have busted. Rods are straight. Where do I begin to figure out how to avoid this in the future? The car is at the shop, I will have to see what length the push rods are. Rockers are those Comp Ultra Gold 19045-16. In the close up shot, you can see where some of the gold got rubbed off....don't know it that helps to figure out what went wrong. The rockers on the other side of the block are in 1 piece, but again have the stress webs in the finish.

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Was the piston to valve clearance checked?
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Joined: December 5th, 2004, 11:36 pm

April 28th, 2012, 10:42 pm #5

Coupe3w has it, pushrods are contacting the rockers near the trunion bearing at full lift.

That being the case its worth checking the underside of the retainer to top of the valve guide/stem seal and piston to valve as well.

You'll need to relieve your new rockers (not uncommon) to stop it happening again....or change brands of rockers.
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Joined: July 12th, 2008, 1:55 pm

April 29th, 2012, 9:40 am #6

Hi cleveland guys, I have 24 miles on the new engine, all low RPM below 3K. 351C with 408 SCAT kit. CHI 4V heads came assembled. What would cause this? Roller cam from MME. All of the rocker arms have stress webs on them. 4 have busted. Rods are straight. Where do I begin to figure out how to avoid this in the future? The car is at the shop, I will have to see what length the push rods are. Rockers are those Comp Ultra Gold 19045-16. In the close up shot, you can see where some of the gold got rubbed off....don't know it that helps to figure out what went wrong. The rockers on the other side of the block are in 1 piece, but again have the stress webs in the finish.

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Re: Broken Rocker Arms
Last edited by gs351 on September 6th, 2013, 8:08 am, edited 1 time in total.
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Joined: May 20th, 2005, 4:48 pm

April 29th, 2012, 11:53 am #7

Hi cleveland guys, I have 24 miles on the new engine, all low RPM below 3K. 351C with 408 SCAT kit. CHI 4V heads came assembled. What would cause this? Roller cam from MME. All of the rocker arms have stress webs on them. 4 have busted. Rods are straight. Where do I begin to figure out how to avoid this in the future? The car is at the shop, I will have to see what length the push rods are. Rockers are those Comp Ultra Gold 19045-16. In the close up shot, you can see where some of the gold got rubbed off....don't know it that helps to figure out what went wrong. The rockers on the other side of the block are in 1 piece, but again have the stress webs in the finish.

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That would be my first guess...

Brent Lykins
B2 Motorsports, LLC






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Joined: February 13th, 2006, 4:59 am

April 29th, 2012, 1:02 pm #8

I just talked to a guy yesterday who had a problem like this and it was the ball on end of rod was bigger than the cup in rockers? This put pressure on rocker and they split? Could that be it?This was on a bb dodge ?
Last edited by steve.k on April 29th, 2012, 1:04 pm, edited 1 time in total.
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Joined: January 22nd, 2010, 3:07 am

April 29th, 2012, 2:07 pm #9

Hi cleveland guys, I have 24 miles on the new engine, all low RPM below 3K. 351C with 408 SCAT kit. CHI 4V heads came assembled. What would cause this? Roller cam from MME. All of the rocker arms have stress webs on them. 4 have busted. Rods are straight. Where do I begin to figure out how to avoid this in the future? The car is at the shop, I will have to see what length the push rods are. Rockers are those Comp Ultra Gold 19045-16. In the close up shot, you can see where some of the gold got rubbed off....don't know it that helps to figure out what went wrong. The rockers on the other side of the block are in 1 piece, but again have the stress webs in the finish.

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You cand see an impact ring on the #6 intake pushrod, and a wear spot at the very bottom of the rocker on the close up pic. You will need to replace all rocker arms, check your contact pattern and geometry, and check clearances. I would go with a different rocker rather than cutting on new ones.
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Joined: July 24th, 2008, 10:06 pm

April 29th, 2012, 3:21 pm #10

I just talked to a guy yesterday who had a problem like this and it was the ball on end of rod was bigger than the cup in rockers? This put pressure on rocker and they split? Could that be it?This was on a bb dodge ?
I had a set of heads done for me a few years ago and they never shortened the valve guides , the retainers were bottoming out on the guides the engine ran for a short time non of the rockers broke but they would have if I had continued to run the engine.
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