I'm wondering if any one has had a similar experience. I have broken two rocker arm studs since I installed my newly rebuilt 302 in September. Thing is, it is the same stud that has broken twice - #3 exhaust stud. It has broken both times near the top. I'm wondering if I've got a binding issue (maybe messed up rocker arm). I'm going to take it by my machine shop tomorrow and let them have a look but am wondering if anyone has had a similar issue before and what may have solved it.

Technical Details:
Cam - Edelbrock 2122 (.448"/.472")
Springs - Comp Cams CCA-926-16 109 seat pressure, 300 open @ 472 lift
Heads - Edelbrock e-street
Rocker Arm Studs - screw-in w/ 3/8" stud
Rocker Arms - Comp Cams Magnum Roller Tip Rockers 1442-16

Thanks in advance!

 

A little more info with a couple of videos to give an idea of what I am looking at. I don't notice any indication of abnormal wear - the rocker is running right in the center of the valve (see video 1). I'll see what the machine shop says. In the mean time, I think I will order some ARP studs to use but it seems unlikely that the stud is the source.

Any and all suggestions welcome!


this Video shows the head and valve

This video shows the push rod, broken studs, ply lock, and rocker arm

 

Check to see if the slot in the rocker is long enough so that it doesn't bind on the stud at full lift. Also recommend that you switch to full roller rockers. Those you bought do not give you any benefit in the roller tip, the real friction reduction is in a switch to roller trunions. The roller tip does little in this as in a stock rocker, the tips are curved and actually roll across the rocker tip in service.

 

Thanks baddad457. So I did check the rocker and the stud out to see if they appeared to be rubbing/binding and I couldn't see any evidence of that... However, I have ordered some ARP studs and when I install the new one, I'll run through a couple revolutions and make sure there is no binding at any point. I'm also wondering if the rocker is hitting the polylock in some way... The more I have thought about it, the more I've suspected the rocker arm may be the source.

As far as full roller rockers go - I actually talked myself out of them before because I didn't think they were necessary for my build, I'd heard people complain about them being loud, and they were a little pricey. However, I agree with your assessment - the roller tip may have some friction reduction compared to a stock rocker, but the real source of friction looks to be in the pivot area where the stud and rocker meet. I am going to revisit this and may switch to full rollers. Do you have a particular recommendation? Will probably be looking to Comp Cams for a recommendation (I'm running their springs and push rods).

So my path forward:

- Get new ARP studs and install with old rocker arm
- Observe rocker all the way through the revolution particularly at full lift to see if slot needs elongated or if anything else is hitting/binding
- If nothing is obvious switch out the rocker arm with a spare roller tip that I have on hand already (same part # so I won't be mixing/matching parts)
- Head over to my machine shop with the truck and all broken studs (I've already spoken with them on the phone. They said to bring it by and let them look)
- Look into a set of full roller rockers. If I end up doing this, I will probably go ahead and upgrade to 7/16" studs. Any opinions on that? Larger studs would be a last resort if I absolutely can't determine any other source. I worry that a thicker stud may only hide the problem/move the problem to the next weakest link.

Surely one of these items will solve the problem. I will post after I go by the machine shop with any updates.

 

It's been a long time since I last bought rockers, but for my 331 (12 yrs ago) I went with Comp Cams "builder series" full roller 1.7 ratio rockers (these were available to pro engine builders then) These use a 7/16 stud. Never had any problems with them. Yea, they're a wee bit noisy (sewing machine noise= they're not that noisy) Also have run a set of Ford/Crane "Cobra" rockers, also 1.7 ratio but are pedestal mounts. this set I bought used 10-15 years ago and had 100K miles on them. Since getting them, they've been run in several motors racking up maybe 60K miles, currently they're in my 96 E150's GT40 headed 351. They show no signs of ever wearing out. Noise ? What noise ? Never heard any to speak of while they were in several 302's in my 89 Ranger. In the van, there's no noise at all. Anyone who thinks roller rockers are noisy are nit pickers. The benefit the roller trunion gives far out weighs any noise you might hear. Ford found a 15 hp gain in the Cobra rockers over the stamped steel ones, some of that was in the increased valve lift, some in the friction reduction in the trunion, and some in the stabilized rocker ratios (the aluminum contruction eliminates any bending in the rocker over the steel stampings.) They also found a significant reduction in engine oil temps. You might also check to make sure your valve springs aren't binding at full lift. Use a feeler gauge to make sure the coils aren't bottomed out at full lift.

 

I've used the Crane/Cobra roller rockers in my 5.0 HO motor for several years, and after an initial break-in noise from the lifters adjusting to the higher pressure from the increased ratio, they have been about as quiet as stock. As to power gains, I would have to say there must be some, as much as a 6% increase in overall lift can provide with the existing cam and heads. The stock SD-EEC had no problems working with them, so the gain could not have been significant. And I could not feel it in my butt-o-meter.

 

Thanks guys for the recommendations.

I got new ARP studs last night, put it back together and adjusted the valves up. Drove it to work and over to the machine shop at lunch. Had those guys look at the broken studs and popped the valve cover off and he looked at everything and listened to it run.

Said there was nothing off about my setup and that there was no good explanation for it. They have recommended if it happens again to go up to 7/16" studs with full roller rockers. They did mention an experience with a 305 Chevy engine that was breaking studs for no reason and when they went to 7/16" it solved the problem. But that guy was breaking studs on multiple cylinders.

I'd like to stick with 1.6 ratio rockers. Comp Cams recommended the Ultra Pro Magnum
COMP Cams: Ultra Pro Magnumâ„¢ Roller Rocker Arms: Ford; 7/16" Stud, 1.6 Ratio

I'll take a look at those mentioned above too before making any decisions.

For the meantime, I'm going to keep driving the truck and see if it happens again - new ARP stud and new rocker arm. I'm hoping that fixed the situation. Stay tuned, it took about 500 miles before any breaks occurred before.

 

Quick question - Could I identify a lifter leaking down by just pressing/pulling on the rocker? Theory being if the lifter was losing prime, the rocker/push rod would begin to have play in it.

Background - While at the machine shop the other day, one of the guys mentioned the rockers tapping when I fired the truck up. This is true as I have noticed when the truck is cold, the rockers will tap for 20 or 30 seconds and then quiet down (I attributed this to the roller tips and its not really loud just a little more noisy than when the engine is warmed up). I called Edelbrock (since I'm running their cam and lifters) and he said it really shouldn't do that if only sitting overnight.

I popped the valve cover off last night after the truck has sit for a couple of days and everything seemed nice and tight - so I rotated the engine so that the valve is sitting in the open position. I'll check again this evening to see if the spring pressure is letting it leak down.

 

If it breaks again, have the machine shop check the valve spring tension. I ate the same lobe off 2 Sig Erson camshafts on my old 351C, found out spring tension was the cause. Apparently when the previous shop did the heads they replaced one of the springs and never said anything about it

 

You're talking here about new lifters in a older engine. No matter what Edelbrock tells you there WILL be some bleed down simply by the clearance between the lifter and the lifter bore walls. That is unless there's a built in check valve inside the lifter to prevent this. Even so, a lifter bleeding down will not cause a rocker stud to break between the time the engine starts up and the oil pressure comes up to tighten the slack up.

 

Funny you say that - I had called Edelbrock back when I was working on the engine yesterday and he said exactly what you are saying baddad. I'm confident now that it isn't a lifter.

As for the springs SparkyAl, I will keep that in mind. I know my machine shop checks to ensure the pressure on the springs is as advertised (I watched him do it), but he did tell me he doesn't check every spring.

I think for my own piece of mind I'm going to go ahead and upgrade to full roller rockers w/ 7/16" ARP studs. Everyone I have talked to has suggested getting rid of the roller tip style - guy at Edelbrock claimed he'd seen that style rocker arm turn studs purple. After all, it's only money

As for the 7/16" upgrade - I know its overkill for my engine but it'll make me sleep easier (and I need to replace my studs with ARP studs anyway.)

One serious lesson I have learned here - Next time I purchase heads, I will buy them bare and build my own setup with quality parts. Even by Edelbrocks admission, the heads are a quality product but they aren't as high quality as their high dollar heads.

I will try to provide an update but as of now, if you don't hear from me it means everything is working.

 

I went with 7/16' studs my 331, course it's running a Z303 roller. All my other small blocks are/were running the puny 5/16" bolts with the pedestal heads (GT40 iron) with both the stock F4TE cam or a B303. All running 1.7 full roller rockers. Doesn't hurt to go big, really doesn't cost any more over 3/8", other than you'll need a new set of poly locks to match the bigger studs.

 

So, it has been a while and I wanted to update on the outcome of this issue for me...

After ~4,000 miles I've had no additional problems. I ended up replacing the 3/8" studs with 7/16" ARP studs, switching to full roller rockers (the comp ultra pro magnum), and I had to get new push rods as well due to the change valve geometry when changing rockers.

I don't suppose I can pinpoint the exact cause, but it certainly seems one (or more) of those three items were to blame.

And for what it is worth, the full rollers are no louder than the roller tips were... IMO, the sewing machine noise is not even noticeable until you lift the hood.

Thanks again for the help! Now on to fight a small vacuum blip at idle

 

The sewing machine sound just verifies you got NO Friction in there !