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I have a 383 with a solid roller. I have a Stud Gridle and i am using the above nuts for the rockers. The problem is that every time i go to adjust the valves i find some of the nuts broken in half Is it from me over tigthening them or what? They never brake when i am actually adjusting the valves so i have no idea why they would brake afterwards. Some input would be great.
Thanks
Marcin

 

Which stud girdle are you using?

Do the nuts break length-wise on the ground diameter? or around the diameter to get a "top" and "bottom" piece?

Is it a clean break?

 

comp cams stud gridle

pretty clean break

 

It appears that there is to much flex at the weak point of the nut, the area where it is reduced in diameter. If you could get slightly longer studs that would protrude another 1/4 to 1/2 inch into the nut it would move this flex point into the "fat" part of the nut. Hope this makes some sense!
If you can't find longer studs you maybe better off without the stud girdles extra weight.

 

It appears to me that a couple of things may be happening:

1) The nut is deeply case hardened or maybe thru hardened to a high enough hardness that repeated bending loads are causing it to fail at shoulder or other stress riser. I'd have to see the failed part in person to tell.

2) The design of the girdle may be such that it loads some nuts more than others because the rocker studs are not in perfect alignment. In this case tightening the girdle draw bolts puts some nuts into bending. They might not fail under installation loads, but cycling loads can then cause the bending failure.

I'd have the nuts analyzed either by Comp or someone else. I'd also check the alignment of the nuts with a straight edge before I installed the girdle. If there was .010 or so difference nut-to-nut I probably wouldn't use the girdle because even it the nuts don't break, you are bending the studs in this case and they may eventually fail.

Here's a case where the cure (girdle) may be worse than the disease ('flexible' studs). How high are you turning your 383? Valve lift? spring P/N?

 

I wanna guess the stud girdle is for a SBC not a LT1 head.... that could add the stress to do this as well since the valve spacing is different.

Bret

 

If you have a set of calipers, check across the studs. Subtract one stud diameter to get the center distance. Put the lock nuts in the girdles, tighten the girdle down so they hold the lock nuts in place. Check across them and subtract one lock nut diameter for centerline.

How do they compare?

There are good and bad girdles just like everything else. As OS mentioned, it could also be the studs themselves. In which case... "no girdle" is your best bet.

-Mindgame

 

Absolutely the right way to check spacing.

Good call, 'Game.

 

illl check it out tomorrow, the problem is i need the gridle to mount the valve covers. the cam is 254/261 with .678 lift on intake and exahust. Rev it to around 6600 right now.
Marcin

 

With cam specs like that, I would look into shaft mounts. I upgraded to Jessel SS series not too long ago, and I will never look at stud mounted rockes again. It was the best money spent on my valvetrain, along with Morel hydraulic roller lifters.



Nick