Shdggsdv

Feel like I'm losing hope at this point. Freshly building this mild engine with new components and everything that can go wrong seems to be going wrong.

This time one of the rocker studs broke clean in half while I was setting timing at idle. I'm a little lost though on what can cause this? I had a mechanic set the valve lash and I'm using Comp 1.6 roller tip rockers with ARP locking nuts. The studs came with the head. Promaxx 2180 aluminum 64cc heads

gbarmore

[QUOTE=Shdggsdv;1596056813]Feel like I'm losing hope at this point. Freshly building this mild engine with new components and everything that can go wrong seems to be going wrong.

This time one of the rocker studs broke clean in half while I was setting timing at idle. I'm a little lost though on what can cause this? I had a mechanic set the valve lash and I'm using Comp 1.6 roller tip rockers with ARP locking nuts. The studs came with the head. Promaxx 2180 aluminum 64cc heads

Not likely, but.... Piston to valve clearance issue?? Is the pushrod bent?

HeadsU.P.

I too have those heads. Not a big fan of those type of locks so I ordered self-locking from Summit. We could talk about poor rockerarm geometry with the 1.6 arms, etc. But I think this was just a fluke. Maybe somebody really torqued the living snot out of that rocker arm during assembly. By any chance, when you set the valvelash did you run out of threads under the nut?

If it were mine, I think I would go ahead and replace ALL the studs with ARPs. I doubt the studs are ARPs on there now, maybe just the nuts are. You sure don't want little parts dropping down the cyl head drain holes.

When you go to order a new set of studs, you will need diameter, top & bottom, thread pitch into the head, thread pitch for the rocker nut AND the distance or amount of threads on the top portion of the stud. Over all length.

Go to Summit and click on camshafts / valvetrain, then rocker studs, you will see what I mean about choices.

NeverTooOld

If you happened to use the shorter roller lifter push rods for flat tappet lifters the rocker arm's slot would be making contact on the inboard side of the stud which would have resulted in the stud getting cut and eventually breaking. Check the other studs for signs of contact because there may be more than one that is failing.

TCracingCA

I have seen some heads enlarged and tapped for larger size and get installed crooked! Basically hand drilled, so they are not quite installed straight up vertical! The other thing is that these actually can move a wiggle at higher RPms and spring pressures! That is why girdles and shaft units were invented! And maybe it was just cheap units!

HeadsU.P.

After looking over the photo a second time I noticed some details worth mentioning:

1. The up-side-down rockerarm bottom appears chipped maybe?
2. Broken adjustment nut shows some threads sticking out but can't tell which end is showing.
This goes back to my question, did you run out of threads setting valvelash?
3. Using 1.6 rockers with a decent lift cam could force the bottom of the rocker to strike the spring retainer.
4. Guide Plate appears stressed just above pushrod. H-m-m-m-m

HeadsU.P.

Another question back to you. Were the valve springs or valvestem seals changed on the head prior to or after the heads were installed? Some of those bad valve spring compresser tools that thread onto the rocker stud can put tremendous stress on the rocker stud, to the point where it can snap off later. Don't ask me how I know.

Big2Bird

^^^^^This

GOSFAST

Couple suggestions, strongly recommend getting rid of those rockers, the "welded-ball" pushrods, and those heavy spring retainers.

Maybe a set of Comp Cam's "tool-steel" retainers, their "Magnum" series pushrods, and some inexpensive stainless roller rockers.

Thanks, Gary in N.Y.

P.S. Not sure if the pushrods are the "culprit" here, but I've seen them break studs on the dyno way back when. Was on a Pontiac at the time with similar "customer supplied" pushrods.

derekderek

and replace the rocker studs. NEVER BUY ASSEMBLED HEADS!! buy castings. buy valves. buy springs... then you know what you have and the manufacturer and the quality. and check the geometry of your setup. and mebbe go back to 1.5 like the small block was designed for.

HeadsU.P.

Another quick question to the O.P. Was a "pushrod length checking tool" used on this setup?

HeadsU.P.

GOSFAST: Those are not heavy retainers. I have a set of those. But you are right about the cheap pushrods. He needs "One Piece".

GOSFAST

That's an opinion, not a fact!!

If they are "chromemoly" they are "heavy".

Thanks, Gary in N.Y.

P.S. A SBC chromemoly retainer weighs about 28 grams (nominal), it's tool-steel counterpart about 19 grams. That's about a 9 gram saving on the spring recovery weight, will take that any day on any build!!

Surfer69

I had brand new stud break on my AFR's like that and it turned out to be a bad heat treat batch that AFR knew about. Not sure who made the studs (ARP/AFR) but they sent me a new batch automatically. 0.02

HeadsU.P.

Ok, ok. Picky-picky-picky.
I meant lighter than GM units.

HeadsU.P.

That reminds me. One out of 16 rocker studs on my ProMaxx heads just didn't act right when setting the valvelash. Threads on the stud looked a little wonkie. Called ProMaxx, they sent three brand new studs, free of charge. I like it when a company stands behind their products, after the sale.

Shdggsdv

So I did use one of those lever-type of spring compressing tools. If they can hurt the studs, that might be my cause.

I did use an adjustable pushrod and my geometry is pretty good.

As for the rocker ratio - I copied an engine build from Hot Rod magazine and they used 1.6 rockers to make 440hp. (Except I used a different set of heads than them). I can switch them to 1.5 if that's absolutely necessary, but I'm using a Comp Cams XE274h w/ .550 lift so it's nothing too crazy.

None of the components look stressed or chipped. What you were seeing was reflections on the oil. All components are in perfect scratch and chip free condition except for the broken stud.

Duane4238

I don't know about that. Looking at the pic, I see something on the bottom of the rocker arm. Just to the left of the roller that rides on the valve stem there is gouging. That would appear to come from the rocker coming into contact with the outer edge of the spring retainer. And that looks like if it contacted the rocker at that point, it would have put pressure on the stud and snapped it off. There was something wrong with the geometry of that rocker assembly.
Duane

Buccaneer

This is right out of the AFR document on their heads. It would appear that they know of stud issues?

HeadsU.P.

If you can, you should look for a valve fully open. Take a feeler gauge and check distance between retainer and rocker. I am not sure what the minimum gap is but maybe someone else does.

What is the story on your valve spring compresser tool? New springs? New seals? When you thread that tool onto the rocker stud, then compress the spring, notice the awkward stress trying to bend that stud.

Also, if you buy new studs take into account that you need ones for guide plates, which need more thread distance under it. You need to get one of those studs out and measure every direction plus thread count. Thats assuming those are the correct studs. (Did the rocker adjustment nut run out of threads?)