I have a strange problem. I broke my second 7/16 rocker stud last weekend with a stud girdle installed. Since this was the second time, I decided to dig a little deeper. I found that the bottom of the polylocks are wearing causing the lash to open up.

After measuing the polylocks they are all different lengths. The one that was on the broken stud as .100 short!

Has anyone else seen this problem before? Where else can I look for a possible cause?

 

springs binding?

 

I doubt it, but I'm going to state the obvious- something is moving... my first thought is are you running 7/16 rockers on 3/8" studs? not tightening the polylocks/studs loose?

 

I am running 7/16 studs. I have lashed the valves to the cam's spec of .025. I'm starting to wonder if my valve springs do not have enough seat pressure for my cam. I'll update you next week after I check them out.

 

I have had and still have the same issue with a 383 sbc. In doing research, the general consensus is valve float or some other harmonic issue. This engine had all new parts(it's about a year old now& currently going back through to step up a little). Running a Howards roller cam which I believe is relatively"old school" so I think it should be easy on valvetrain. Comp Endurex lifters with Manley pushrods activating Howards rockers. AFR 210 Eliminators with Comp porting using the springs that came on the heads which are slightly stronger than what Howards recommends. When it first started it & I figured out what it was, I layed blame on the adjuster nuts that came with the girdle(Jegs brand). Some more cheap Chinese stuff I figured! So I got a set of ARP adjuster nuts-PosiLocks I think, these ought to be good for about 175.00 a set! And they are, the lash hasn't moved much at all in 40 passes. But when I tore it down to freshen, the bottoms of the ARPs are starting to fragment ever so slightly. As a matter of fact,I was getting the tiny fragments in the moroso screen on top of the oil filter, I never could figure out what they were until I took it apart.Using my 10X spark plug viewer, I could tell they were shiny chrome-like, slightly curled, and blue on the edges.Like they were hammered out.They were also magnetic.Anyhow, after seeing that I checked the valve springs and they are on the money.Also the geometry is fine, & the valve stems don't show the star pattern of valves dancing.So at this point, I don't really know.It's gonna be a couple more months probably before I get back on this project so I guess I'll study it some more then.Good luck with your adventure & let us know what you come up with.

 

how much room do you guys have before coil bind with the cams you are running? spring type? installed height?

 

I am running Jeg's springs and they do not list a coil bind number. They came preinstalled in my heads. It does say that they support a max of .680 lift. I am really close to that. I have a 630/630 solid roller cam. So with my 1.6 rockers that makes it a .672 cam. Only being 8 thousanths from the max I very well could be getting into some coil bind. I am waiting on a response from Jeg's on the actual coil bind number.

 

I'd say you found your problem.

 

I usually set bracket drag engines up with .100 clearance. Truck pull or wilder drag engines I will tighten up accordingly.

 

springs that are good to .680 doesnt necessarily mean they will be good to .680 when they are installed on a set of heads. you have to take into account the installed height.
valve stem length, valve job, spring pocket machining, retainer type, lock type, and some other variables will change your installed height. gotta measure that so you'll know where you stand.

 

I understand what goes into the max lift calcuation. However these haeds came assembled from Jeg's so they should know what the numbers are supposed to be.

I am going to take double check all the numbers they gave me this weekend. I'll let you know what I find out.

 

My guess is if Jeg's set them up they just put then together because the average jegs cyl head buyer will not have a cam that big. If there is issues, they will tell you the cam is too large or you should have checked them out with the clearances that close. .008 clearance is crazy escpecially when they are a box set of heads. Breaking a stud with girdles show's a definite problem.

 

Yeah, yours is close enough that you need to take some springs apart & check the installed height & also see where coil bind occurs with the spring itself. Don't take anyones word on it.

 

I took everything apart last night. I am not getting into coil bind and I have penty of clearance.

The heads I have use offset rockers. The rockers side load before actually lifting. I am thinking the rockers are actually the cause of my issue. the poly locks are even worn on an angle. I'm going to look into getting a set of shaft rockers.

 

was going to say. dont forget to take the lash out of the total lift also. so you would have more then .08

in the past i have seen studs brake just the tip off inside the poly lock. parts to hard..brittle.(studs)

with the locks eating them self. i have seen miss matched locks and rockers used.
= most of the time roller rockers have a cut in them to match the lock OD.come has a set.
if the lock is to larg a OD then this can lead to the lock riding on & off the edg of the rocker shaft.w/a larg lash.= eating its self.
also this will hapn if the rocker shaft is up side down..other times it just to soft of a part..

just a few things to look at..

 

why are you running offset rockers? what kind of heads do you have?

 

They are really Canfield 220 heads. Jeg's bought them out and put their name on them.

 

So I have figured out my problem. My rocker arms have been hitting the polylocks at full lift. I took all the rockers off and clearanced them.