Rocker nuts keep breaking...HELP!!??

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 30, 2006

#1

• Jul 30, 2006

• #1

Ok, so I've my motor(in my sig) keeps breaking rocker nuts. I have stud mount roller rockers, and the polly lock part of the top of the rocker nut will break off. It's already happened like 2 or 3 times in the past few months, on different valves, but all on the same bank, and I'm not to sure why... It does have a trick flow stage 2 cam, but there is obviously no P/V clearence issues... Before I put the cam in it didn't do this either, and no it will only do it if I over rev on accident...at about 7K, as i usually shift at 6K or 6.5K, but before it also wouln't do this w/ my old cam. My buddy told me that with a big cam like that then I would need shorter pushrods, but I'm not sure. Any help appriciated...

 

M

Mike92GT

Founding Member

Jan 23, 2002

583

0

0

Florida

Jul 30, 2006

#2

• Jul 30, 2006

• #2

Thats strange. What length pushrods are you using? How many threads are the polylocks grabbing before you tighten the lock nut? I would assume that you have 3/8" studs. With that kind of RPM maybe you need to look into getting some 7/16th studs and rockers.

 

dastang2

Active Member

Dec 11, 2003

2,020

0

46

tx

Jul 30, 2006

#3

• Jul 30, 2006

• #3

can't be the pushrods, if it was, both sides would have broken nuts. how sure are you that you don't have a bent valve or 2. something is making this happen over and over. i think it could be a bent valve.

 

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 30, 2006

#4

• Jul 30, 2006

• #4

Yes, I do have 3/8th studs, and the heads were just red done with a full valve job, and one of the valves were replaced. If i had P/V clearence, then wouldn't that be evident on all the valves, not just one or two...The poly locks do thread a ways onto the stud, so i don't think that could be it...

 

Rick 91GT

Mustang Master

Nov 29, 1999

9,692

95

99

PA

Jul 30, 2006

#5

• Jul 30, 2006

• #5

Check the valve spring pressures if they are weak and you over rev the cam it will float and you will have PTV issues., Recheck the geometry for the correct pushrod length as well.

If your breaking the nuts you have an issue that you need to find, something is binding. What about radial clearnace on the rockers? What brand rockers? What brand nuts?

 

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 31, 2006

#6

• Jul 31, 2006

• #6

The rockers are the ford racing A351's and their 1.6 ratio. The nuts are poly locks and I got them from comp cams. I'm not sure what u mean by radial clearence on the rockers, and the valve springs are 10 years old, from trickflow. I don't know what size the pushrods are, but I just used the same ones I used before with the TW heads, with a smaller cam.

 

Rick 91GT

Mustang Master

Nov 29, 1999

9,692

95

99

PA

Jul 31, 2006

#7

• Jul 31, 2006

• #7

Radial clearance would be between the spring and the rocker, most of the ford rockers are not cut back very far so a 1.46" diameter spring could hit and bind.

You need to verify the pushrod length using a adjustable pushrod, also verfiy the geometry of them as well. 10 year old valve springs usually are very worn especially with a cam like the Stage II thats needs 145lbs or so on the seat. What is the installed height of the spring, do you know your current seat pressures?

My bet is the springs were floating causing it to bind and hit.. When the machine shop fixed your heads did they tell you what they found as to why you bent the valve?

 

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 31, 2006

#8

• Jul 31, 2006

• #8

The valve they replaced was replaced because of excessive carbon buildup due to a broken valve guide, which caused the valve to bend. I have only had the TFS stage 2 cam in for a few months now, and before I had a much smaller cam, not sure which one... How would i measure this radial clearence?

 

R

R2D2

Jul 31, 2006

#9

• Jul 31, 2006

• #9

take a quick read and see if anything pertains to you. You have a binding issue somewhere thats not gonna go away by itself

http://sbftech.com/index.php/topic,150.0.html

 

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 31, 2006

#10

• Jul 31, 2006

• #10

Thanks for the info...Do you think a stud girdle would be worth adding? To keep the rockers from flexing at high rpm?

 

R

R2D2

Jul 31, 2006

#11

• Jul 31, 2006

• #11

I ran a bunch of crazy **** to silly rpm's back in the day with no girdle, the absense of a girdle is definately not your problem.

 

dastang2

Active Member

Dec 11, 2003

2,020

0

46

tx

Jul 31, 2006

#12

• Jul 31, 2006

• #12

i didn't know a valve could bend because of carbon buildup. it should be the other way around, the valve got bent and then broke the guide. that's just me, i don't know much about this kind of stuff but that seems odd to me.

 

M

my289eatsrice

New Member

Nov 11, 2005

121

0

0

Woodstock, CT

Jul 31, 2006

#13

• Jul 31, 2006

• #13

No, well not exaclty. The combustion chamber wasn't sealing, and that allowed the cylinder to become washed down due to oil flow through the broken valve guide. Eventually enough carbon bent the valve, or thats what I'm assuming what happened