I'm on my second set of poly-locks which are from Comp Cams that replaced an unknown brand that I thought where just cheapos, but now these are breaking!! They are breaking about 1/8" down the nut, right where the nut part stops and the rest is smooth.

This is on a solid cam and I'm lashing at about .028" cold. After the first one broke, I thought it might be because I'm tightening them too tight, but I relashed everything and did not feel I put a lot of strength into them this time. To me it makes no sense for them to break where they are breaking...

Thanks,
Bill C.

is it above or below the setscrew? If it's above the set screw that would be really strange. Rockers hitting the polylocks?

Tom

IO replaced mine because I way overtorqued the last set. But never split one. Something is amiss. If they're rollers are you sure you have the flat side of the trunion pointing up? ( BTDT!)

They are breaking right about where the end of the set screw would be...

That's an interesting idea Tom... the rockers hitting the polt-locks... have to check that today!

Gene,
They are CC roller-tip rockers, not full rollers. Pretty sure I got them on there right!! ;)

Thanks, stay tuned as I got a new set of the Crane ones today to try out.

Bill C.

Bill,
How far down on the stud is the nut going ?? The setcrew should be just barely into the polylock body. If it is way down because the polylock is only on the stud a few threads, it could be flexing and causing it to break. Solution is longer studs.
I personally would rather use the stock type locking nuts that come with the rockers. I hat polylocks, have seen too many of them break or come loose. This thread reaffirms my feelings.
Hope this helps,

Bill,
Thanks for the info, I'm beginning to feel the same as you on these!! However, I do think the majority of the problem may be the fact that I was tightening the ploy-locks too tight. I was cranking them down pretty good whereas I think they should only get about 25 or so ft/lbs. Last night I re-did them all and went back to the first set I bought which are longer and the set screw fits in them better... all the way covered up. I'm curious as to why you say the set screw should only barely be into the nut?? Seems like that would not be very safe or reliable?!! I have had three different sets of locking nuts now, a 'generic' set that I got from a mail-order place when I bought a bunch of other stuff, then a set of the CC ones and just bought a new set of the Crane ones. The first set were the longest and the set screw was fully seated into the nut when adjusted to the correct lash. The CC ones were a little shorter and the set screw had about 1/3 of it's upper body sticking out of the nut. The Crane ones were about and 1/8" shorter yet and the set screw was only in about 1/4 of it's length, so I was hesitant to use them. Again, I went back to the original set I bought and filled in the 3 broken ones with 'regular' stock type nuts.

I hope all this solves the problem... I guess I've learned a thing or two!! The car is probably going to be sold tonight, so I hope the new owner does not have any trouble with them!!

Thanks again,
Bill C.

BC,
if you've still got the engine... i had an problem with the Comp Cams Magnum Roller tip rocker arms hitting the nuts. they were Crane Cam Kool nuts (they're pretty wide). machine shop caught it, some thinner rocker nuts from Manley solved it.

you wouldn't happen to have .100 long valves would you? if that's the case then you're lucky you're breaking the nuts instead of the stud. as someone else suggested you may need longer rocker studs.

71BB,
These were not the 'Cool Nuts' just regular locking nuts... same size as the CC ones and 'other' set I have. I did check for clearance between the nuts and the rocker arm and had at least 1/8" all around in all positions of the valve, so I don't think they are hitting each other.

m71,
The valves are standard length and the position of the roller tip on the valves looks perfect. I definitely don't need longer studs... if anything, these studs are too long already!! If they were about 1/2" shorter, then the Crane locking nuts would have worked good.

Like I said before, I think it was probably just me torqueing the nuts too tight.

The car looks like it will be gone tomorrow night.

Thanks again,
Bill C.