COMP cam magnum rocker nut failure
 

So I took the car out for a little spin today. I had installed Magnum roller rockers , guide plates and pushrods about 100 miles ago. I have a medium lift hydraulic cam in the motor....nothing too radical. I left from a light with a little of go petal and the car popped a couple of times and I backed out right away. The car immediately felt like it was down a cylinder. I pulled over and checked for anything odd. There were not any strange noises at idle and oil pressure was still good. I went straight home and could tell something was off in the motor. If I brought up the RPM's, I would get a little rattling out of the drivers side front of the motor. I let it cool down and pulled the plugs to check for anything nasty. #1 plug was black and wet, others all light tan and dry. I pulled the valve cover and found the pics below.
http://i20.photobucket.com/albums/b2...r/100_4848.jpg
http://i20.photobucket.com/albums/b2...r/100_4852.jpg
http://i20.photobucket.com/albums/b2...r/100_4854.jpg

Has anyone seen this from COMP products before? Any ideas on a better product that's not going to do this on another pushrod? Needless to say the metal is nowhere to be seen in the cylinder head. I am hoping it's in the pan. I have a magnetic plug so my fingers are crossed.

Is it just me or is there a serious lack of oil up top in that motor.......

I see that a lot from my customers tightening up the set screw then overtightning the whole deal by pulling on the adjuster nut to make sure its *tight*. This actually puts all the pressure on the lower threads of the adjuster nut and it cracks.

Originally I had it adjusted at 1/2 turn past snug and it popped a little. When I adjusted to 1/4 turn past snug it ran much better.

Hydraulic cams only run preload to keep the noise out. The more preload you run the better you chances of getting the lifter *pumped up* if you float the valves. If you plan on takeing it past 6500 rpm adjust them to zero lash. othe rthan the 1/4 turn of preload is fine.

As for you black and wet in that hole it would most likely be from oil going past the valve guide and seal. Since you lost the intake rocker the piston was trying to suck on that stroke yet had no air/fuel.

I am using the stock studs with the COMP parts. I wonder if maybe the stock studs need to be upgraded to a longer stud to get more thread engagement for the adjuster nut and take off some of the stress.

The set screw in the adjusters do look like they are low. I use ARP ones on BBC engines we build.

Your valve adjustment and what he is referring to are two different balls of wax. I'm assuming this is a hydraulic cam? Adjust the valve with the set screw loose, snug up the set screw, and then give the nut a hair more with a 9/16 wrench. If you are using a big ratchet or a super long wrench, you could over tighten the poly locks and crack them just as he said.

Maybe that's the issue......not enough length on the rocker studs. Any idea how much longer the ARP ones are over stock?

Yes....moderate lift hydraulic cam. I adjusted the nut down, set the screw, and gave the nut another 1/4 turn.

I agree, not much thread engagement. You are only getting to the shoulder.

Now don't forget pushrod length also contributes to where the rocker will sit on the stud. Did you check geometry or is this all *stock*

You can go to ARP's site and get the length or i can measure a set tomorrow for you.

I just found a pic of where the adjuster should be.

http://gallery.bigtimeauto.com/album...ters.sized.jpg

From your pic, mine are way too low in the nut. These pushrods are Magnums as well....just a hair over 8 1/4" in length. Studs are stock, guide plates are COMP. Stock BBC heads.

ARP site says 3/8" should be 1.895 with roller rockers vs 1.750 stock length.

I can measure the arps in the morning for you. Im out of here now.

So I picked up the new 1/4" longer ARP studs and ARP keepers today. I still think there may be an issue. The nut takes 5 1/4 full turns before it bottoms out on the rocker. The allen screw takes 8 full turns before it bottoms out. Is this still too deep? They are not even close to Bigtime's pic above. I had the pushrod length checked and they are the correct intake and exhausts.
http://i20.photobucket.com/albums/b2...r/100_4855.jpg
http://i20.photobucket.com/albums/b2...r/100_4856.jpg

Apparently, the rule of thumb is that the amount of thread engagement should equal the diameter of the stud.

Any updates on the stud / rocker issue? What did you end up doing to resolve it? Were you able to get enough thread engagement to equal the stud diameter?

I installed the longer ARP studs and hardware. 5 1/4 turns is juuuust equal to the stud diameter so I think I will be OK. I ran the car and it sounded good but have not been able to take the car out yet on the road. it did smoke a little from having no intake valve opening while the car was running without the rocker. Hopefully I can put some miles on it and see if it holds together. (fingers crossed)

Good luck!

Good luck I'm hoping for the best for you.