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Mark's curse transferred or valve train failure(s)

T

Tims65

Member
I spent the day last Wednesday flogging my car out at Summit Point with the Shelby Club. She ran great all day (video found here - http://www.stangfix.com/testforum2/inde ... 4.html#new
), that is until I tried to drive home. Coming over the bridge, I started to hear a little valve tap; just before the exit gate it turned into a loud clatter. I shut her down and pulled over to the side of the road. I pulled a valve cover to have a look and one of the rocker arms was off and laying in the head. I thought that a nut had backed off. On closer inspection, I determined that the 3/8" mounting stud had broken.

I couldn't replace the stud, so I was stuck with leaving my car there. There was still one shop, at the track, open. I cleaned up the parts, snugged the valve covers back on and drove up to the shop and left my car for a shaft replacement.

After getting home and looking at the pictures I shot, I noticed that I had more issues than just the broken stud. If you count the broken stud as 1, then look at rocker 2, you can see the roller tip is in place. Also, on rocker 2, you can see the pin extending on both sides of the rocker. When I look at rocker 3, the roller tip is missing and the pin is pushed all of the way out of the right side.

One other thing I noticed is, there seems to be some wear/contact on the right side of rocker 2 in the 3rd picture.

I'm looking for some guidance, please.


photo2.jpg


rollertipfailure.jpg


studbreakrockercontactwithpoly.jpg
 
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Overtightening the rocker studs ??
Coils are binding at high revs ??
( wild guess )
 
Ouch, sorry Tim. Been there, done that, switched to a shaft rocker setup.
 
Out of curiosity, what are the brand of those rockers? Years ago I broke a stud several times but it was due to running stock rockers with a high-lift cam & supposedly binding against the slot, which is not your problem.
 
Okay, So a little more information on my rocker stud brake, rocker roller tip failure and rocker/polynut contact. I sent a rocker to Comp Cams and it turns out these are not Comp Cams rockers or Comp Cams studs or Comp Cams push rods (all of which I was sold when I contracted my engine build).

It seems that the 'comp cams', made in China, rockers do not have the proper clearances and the rockers contacted the push rod, probably stressing the stud(s). All of the rockers have a groove worn in them by the push rod.

contactwithpushrod.jpg



cf0fe28c.jpg



The one, sole rocker (bottom left) without the push rod groove is an actual Comp Cams rocker, that I put on to get my car home.
 
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So today I checked my existing push rods this afternoon. I marked out the top of several valve stems with a black sharpie, then rotated the engine 3 full rotations. Here are the marks I got:

#2 Intake valve

13313a8b.jpg




#2 Intake valve

d2df9a9b.jpg




#3 Intake valve

c847a0b9.jpg




#3 Exhaust valve

3eabc276.jpg
 
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All of the Intake marks are just in board of the valve stem Center Line.
All of the Exhaust marks are just out board of the valve stem Center Line.

This is consistent with my Cam profile:
Intake Lift - .566
Exhaust Lift - .571

Intake SAE - 281
Exhaust SAE - 285

Intake @.050 - 232
Exhaust @.050 - 236

The Intake lobe has slightly less lift than the Exhaust lobe. All of the push rods are the same.

CIMG3101.jpg


It looks like my engine builder split the difference of the lobe lift when picking the push rods, instead of picking the optimum length for the exhaust and then the intake.

My question is do you think these settings are within an acceptable tolerance?
I have the car back together and running and it sounds fine.

Thanks,
Tim
 
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I would think the intake needs to be more centered. It doesn't look from the pictures that the mark ever crosses over the centerline.
 
I agree with ^^^, the intake is too close to the edge. The lift on my (previous, unblown-up engine) cam is the same for both intake & exhaust so I could use the same pushrods.
 
"Tims65" said:
Okay, So a little more information on my rocker stud brake, rocker roller tip failure and rocker/polynut contact. I sent a rocker to Comp Cams and it turns out these are not Comp Cams rockers or Comp Cams studs or Comp Cams push rods (all of which I was sold when I contracted my engine build).

It seems that the 'comp cams', made in China, rockers do not have the proper clearances and the rockers contacted the push rod, probably stressing the stud(s). All of the rockers have a groove worn in them by the push rod.

contactwithpushrod.jpg



cf0fe28c.jpg



The one, sole rocker (bottom left) without the push rod groove is an actual Comp Cams rocker, that I put on to get my car home.
Click to expand...

Just for understanding... the engine builder put in Chinese parts when Comp Cams were specified??? It wasn't a case of Counterfeit items sold in Comp Packaging???
 
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"dm289" said:
Just for understanding... the engine builder put in Chinese parts when Comp Cams were specified??? It wasn't a case of Counterfeit items sold in Comp Packaging???
Click to expand...


Hmm, somehow I overlooked that they used Chinese knock offs instead of what you specified. Somebody's got some splain'n to do.
 
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