HICKL Posted February 17, 2010 Share Posted February 17, 2010 Was pushing it pretty hard yesterday and all of a sudden, bang bang bang bang...etc etc. coasted to a stop expecting to be leaving a trail of oil. no trail. I figured I must have dropped a valve and was bouncing off the piston. Got her home today and pulled the valve covers expecting to verify my theory. Pulled the drivers side valve cover off and one of my roller rockers falls out on the concrete. Long story short, number 2 cylinder exhaust side rocker arm stud broken. In my limited hot rodding experience, I have never seen this happen. Is it common? Is it an indication of a bigger valve train problem? Could I be so lucky that my motor is not hurt by compressing a cylinder over and over without the exhaust valve opening? If all else is good, what studs should I buy? Running sportsman II heads with whatever studs came in them. Thanks guys Jeff Quote Link to comment Share on other sites More sharing options...
sweetride2go Posted February 17, 2010 Share Posted February 17, 2010 I had a rocker stud come out once, but never broke one... Mine just started tapping like mad and then it went quiet and simultaneously dropped a cylinder. I was relieved to find such an easy fix when i pulled the valve cover! Quote Link to comment Share on other sites More sharing options...
jt1 Posted February 17, 2010 Share Posted February 17, 2010 I've broken several. So far I've had no other damage. It can make a heck of a racket when the lifter falls down on the cam. Look the cam lobe and lifter over very closely, make sure the rocker isn't binding on anything or bottomed out on the threaded portion of the stud. Usually you can replace the stud without any other issues. jt Quote Link to comment Share on other sites More sharing options...
mark Posted February 17, 2010 Share Posted February 17, 2010 I've broken a few also. Ended up replaceing the lifters (originals with unknown mileage) and have not broken any since. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 17, 2010 Share Posted February 17, 2010 rockers and rocker studs rarely if ever break for no reason, theres almost always without exception, a clearance or geometry issue, thats the cause, if you have not verified all the clearance issues Id strongly suggest you look into that. http://forum.grumpysperformance.com/viewtopic.php?f=52&t=689&p=7416#p7416 Quote Link to comment Share on other sites More sharing options...
dustin280zx Posted February 17, 2010 Share Posted February 17, 2010 There were no bent pushrods? Quote Link to comment Share on other sites More sharing options...
Zfan1 Posted February 18, 2010 Share Posted February 18, 2010 Grumpy is dead one. Rarely do you break one and not find another problem that is the root cause. Check valve springs, push rods, rockers and guide plates, lifters and hopefully the cam is ok! Quote Link to comment Share on other sites More sharing options...
HICKL Posted February 18, 2010 Author Share Posted February 18, 2010 I have not had a chance to touch it since I got it home. The pushrod on this valve was fine (have not looked at the others). I am running some pretty stout pushrods. I just find it hard to believe I have a fundamental problem as I have been driving this car with this motor for a few years now. These heads are probably 6 years old or so. Will see I guess. I have to buy new studs regardless, should I just go with the ARP ones? Quote Link to comment Share on other sites More sharing options...
Slopoke Posted February 18, 2010 Share Posted February 18, 2010 I had a buddy push his rocker arm stud through the rocker arm itself... made the same popping noise and wouldn't drive. Swapped out the cam and heads (which he was going to do anyways) and hasn't had a problem since. Quote Link to comment Share on other sites More sharing options...
roye@hrewheels.com Posted February 18, 2010 Share Posted February 18, 2010 You may want to check your valve lift and compare it against your Retainer/Valve guide clearance. Ive seen plenty of aftermarket heads that dont have the same guide height all the way across. Also, check to make sure that the valve moves down the guide, you could have siezed the vale in the closed position causing the stud to break. Quote Link to comment Share on other sites More sharing options...
HICKL Posted February 18, 2010 Author Share Posted February 18, 2010 I checked the valve as soon as I saw the breakage and it was free. Quote Link to comment Share on other sites More sharing options...
John Scott Posted February 20, 2010 Share Posted February 20, 2010 I run 7/16 screw in studs just for this reason. Do you have 3/8 or 7/16 Quote Link to comment Share on other sites More sharing options...
GRUMPZ Posted February 21, 2010 Share Posted February 21, 2010 My builder insisted on 7/16 studs . 3/8's are not strong enough and will break even if everything else is right. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 21, 2010 Share Posted February 21, 2010 (edited) My builder insisted on 7/16 studs . 3/8's are not strong enough and will break even if everything else is right. IM always amazed at the guys that think swapping from 3/8" to 7/16" rocker studs is going to be a huge improvement,in valve train stability,now theres not the slightest doubt that an increase of about 18% in cross sectional area on the studs a significant increase in strength, and while that helps, its not the huge improvement many people think it is because its generally not the rocker studs that fail from flexing,unless they are defective, as most would have you believe, but because its the rocker geometry and rocker support not the stud diameter, that matters, more, you can,t expect a rocker stud with one end unsupported to have any where near the resistance to deflection that a rocker stud with BOTH ends supported will have. if you support both ends of the rocker studs you easily increase the load bearing capacity to far more than the additional stud diameter increase, can ever do,having one end unsupported the stud acts a bit like a nail being pulled by a hammer, in that loads applied to the upper end tend to both bend the nail and pull on the lower end , thats where the use of STUD GIRDLES comes into play. simply supporting the rocker stud tips so that the forces acting on a single rocker stud are now opposed by the resistance to deflection of all 8 rocker studs is a huge improvement http://www.summitracing.com/parts/SUM-141010/?rtype=10 http://www.summitracing.com/parts/CCA-4014/ Edited February 21, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
fast-datsun Posted February 22, 2010 Share Posted February 22, 2010 Make sure rockers are NOT hitting the stud at full lift..... that is what brakes alot of them... Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 22, 2010 Share Posted February 22, 2010 (edited) Make sure rockers are NOT hitting the stud at full lift..... that is what brakes alot of them... Thats an,excellent point thats often over looked as is, verifying valve spring coil bind, push-rod to head clearance ,rocker to retainer and retainer to valve seal and piston to valve clearance issues and, just successfully rotating the engine without it binding up is NOT checking clearances Edited February 22, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
HICKL Posted February 23, 2010 Author Share Posted February 23, 2010 I was wondering why nobody had suggested stud girdles yet, I expected that right off. As far as checking rocker to stud clearance, how would you do that other than just rolling it over and watching. I don't see any marking to indicate that this was the problem, but at the same time, can not rule out that at 7000 rpm, these things are not flinging around more than at 50 rpm when I am looking at it. Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 23, 2010 Share Posted February 23, 2010 (edited) I was wondering why nobody had suggested stud girdles yet, I expected that right off. As far as checking rocker to stud clearance, how would you do that other than just rolling it over and watching. I don't see any marking to indicate that this was the problem, but at the same time, can not rule out that at 7000 rpm, these things are not flinging around more than at 50 rpm when I am looking at it. the quick easy route is to take a bit of uninsulated 12 ga solid core copper wire and make a (U) shape,with about 4" legs , you then bend the ends into a (J)at 90 degrees to the (U)the ends are placed (hooked into)in the rocker slot from the lower side of the rocker between the stud and rocker slot and the engines spun manually by a friend while you hold the wire in the rocker for two full rotations, if the wires not pinched your good, check the next rocker, if it gets crimped you need to lengthen the rocker slot Edited February 23, 2010 by grumpyvette Quote Link to comment Share on other sites More sharing options...
HICKL Posted February 26, 2010 Author Share Posted February 26, 2010 I looked at the bottom of some of my rockers, especially the one that came off, and there is no sign of any contact on the lower side. I would think it would show if it had ever hit because the anodize or whatever the coating is is visibly scuffed up on the tops just from the socket hitting them when I install. Quote Link to comment Share on other sites More sharing options...
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