New Engine Build - Huge solid roller valve train issues...

[n20capri]

Dad just had a new 363 built. First start it breaks a rocker stud after the engine gets hot. About enough time to get it up to temp and burp the cooling system. Engine builder says that happens from time to time. I don't buy that but he gives us a replacement and we get it going.

Start it up after replacement and drive it 2 miles - all seems fine. We had a broken vacuum tree that we had to tape so we didn't want to drive it far.

Fast forward to today. 14 miles later and it breaks another rocker stud. Literally going 40mph and it just went. Exhaust stud again on a different cylinder though. Now I'm noticing you can see where the poly lock is hitting the rocker. They are ALL like this. (see pic)

Huge lift cam (691) - is this is sign of a rocker with not enough slot? Or something else? Something clearly ain't right. Just trying to educate myself before we go back to engine builder. He was very nonchalant about the first one. Seems like a huge deal to me.

Please help!

[Hissing Cobra]

Pushrods too long or too short? What size are the rocker arm studs, 3/8" or 7/16"? On my 306, I have 3/8" studs and I broke one at the track, which we were able to replace and it's been fine since. On my 347 with the bigger cam and more stress, we went with the 7/16" size. With your 363 and big cam, I would think that would be the size you'd need. Make sure the pushrod length is correct!

[4-barrel Mike]

Valve spring coil bind?

Mike

[brianj]

Valve spring coil bind?

Mike

Sounds like it. And i agree that .691 lift is pretty stout on 3/8 studs. I'd definitely be checking the valve train geometry on this pretty closely.

[n20capri]

It's definitely a 7/16 stud. So nobody thinks it's just a rocker issue and I need a better rocker? Just trying to figure out what I'm going to want the engine builder to offer me to make this right.

[n20capri]

I'll also note that the car seems to run fine otherwise. Didn't beat on it. One short 3Rd gear pull to 6000 that's it. Just trying to get break in miles on it.

[grabbergreen84]

What rockers are they? I've read here that some rockers sold for small block Fords are really off-the-shelf pieces which were designed to fit Chevys!
JACook has written about this, and the gist is that if you end up with the re-purposed Chevy rockers on your SBF, you will never get the geometry exactly right, and be forever prone to things like broken rocker studs.

[n20capri]

These are COMP cams pro stainless rockers. Dad ran these exact rockers on his previous 347 with NO problems.

[Jerry peachuer]

Trunions rotated correctly to seat the poly lock ?

The screw in studs what brand are they

[n20capri]

Trunions rotated correctly to seat the poly lock ?

The screw in studs what brand are they

Yes...arp

[Jerry peachuer]

In the initial pick that shows the poly lock bottoming out appears to have the trunion rotated 180 from where it should be

The poly loc is supposed to sit on the flat part

If this isn't the case then I would look at the rocker arm inside body possibly hitting the valve retainer at almost max lift

Not sure on these comp rockers but I'm certain you have a very serious valve spring and it's pretty large in diameter I would imagine

Just make sure there's clearance there that's a serious cam

I would look into ARP rocker studs also

There's rolled threads and cut threads and your pic looks like those are cut threads on the rocker stud (they are sharp and almost come to a point
These are weaker threads period no matter what brand you use

But you have some serious stresses on those studs with that lift cam

[n20capri]

That pic was taken after I pulled everything off the head and it was still piping hot...I probably just put them together wrong but I will look again to make sure Trunions are correct but I think they are.

So frustrating.

At this point what should I expect from the builder. I'm wanting him to come to the house to check the geometry personally. Dad only lives 5 min from shop. Not sure if that's reasonable though. Dad and I are experienced but not with setting up solid roller high life valve trains.

I won't get into details but this isn't the first issue with this new combo either. Trying to figure out what to expect and how pissed we should let him know we are. Lol

[n20capri]

Also...last motor he built for dad was perfect. Zeros issue. 12 years of nitrous blasting fun...it owed us nothing.

[Walking-Tall]

Now I'm noticing you can see where the poly lock is hitting the rocker. They are ALL like this. (see pic)

Actually, the rocker moves, it's the rocker that's hitting the poly lock. Even if the poly locks are installed correctly, on the flats, that's still too close for comfort, and I'd say the push rods are too long, causing over-travel opening. Installation and geometry definitely needs examining...

* Additionally, regardless of camshaft size or spring strength, there's far more tension on rocker studs than a bending moment. The rocker arms "shoulder" the majority of the bending. IMHO, it's incorrect geometry/installation, and the obvious collisions like seen in your picture that caused the first stud to break, from forced stud bending (and/or in conjunction with valve spring coils stacking solid), as likely will break subsequent rocker studs if left as is. It must make a helluva racket running, though with a mechanical cam with lash, those contacting collision noises maybe aren't noticeable.

[Jerry peachuer]

I get the frustration part and respect not all things go as planned

To be a repeat customer and sounds like him and pops are somewhat close I think there's a good chance for the house call the very lease

keep a cool head its only a stud or 2 and awesome job for shutting it down before carnage happened

Your spring pressures no joke so if there not a high quality type stud then I would take that into account first
Second I would look very closely on dis assembly it's your only chance to get a look at what happened before you scratch your head

Also your poly loc diameter has to be the right diameter for the roller rocker slot other wise it could shoulder out on the inside slot as in your pick

just some ideas that don't cost anything but your time

[Zap's 85 GT]

Measure for rocker stud deflection and run a checker valve spring to check for binding.

Are the poly locks you are using the ones that came with the Pro Magnum rockers? The ones hat came with mine has a smaller diameter base where it attached to the pivot trunion. It should not be making those marks.

Like the ones on the right. But not cracked.

[Jerry peachuer]

Wait are those pressed in studs ?
Are they pinned in the head ?

Reason I'm asking is in your pic I see the rusty shank is that the part that goes into your head?

If so you may have to go to a screw in type stud not the press in type
(Or at least I would)

I also agree about the comments with the pushrod lengths being correct very critical

[Walking-Tall]

Wait are those pressed in studs ?
Are they pinned in the head ?

Reason I'm asking is in your pic I see the rusty shank is that the part that goes into your head?

Pretty sure that's a valve cover bolt.

[Jerry peachuer]

Thanks walking tall

[brianj]

Pretty sure that's a valve cover bolt.

Lol. It threw me for a bit, too, though.

[Walking-Tall]

Thanks walking tall

.............

[Walking-Tall]

lol. It threw me for a bit, too, though.

............... :d

[Mustang-junky]

You should be using a stud girdle for a cam as stout as what you have. Double check the push rod length.

I use locks like these with a girdle.


Your rockers might need a smaller shank on the nut. Are the nuts you used what came with the rockers?

Jess

[n20capri]

Thanks to everyone for replies...much appreciated...

Actually, the rocker moves, it's the rocker that's hitting the poly lock. Even if the poly locks are installed correctly, on the flats, that's still too close for comfort, and I'd say the push rods are too long, causing over-travel opening. Installation and geometry definitely needs examining...

* Additionally, regardless of camshaft size or spring strength, there's far more tension on rocker studs than a bending moment. The rocker arms "shoulder" the majority of the bending. IMHO, it's incorrect geometry/installation, and the obvious collisions like seen in your picture that caused the first stud to break, from forced stud bending (and/or in conjunction with valve spring coils stacking solid), as likely will break subsequent rocker studs if left as is. It must make a helluva racket running, though with a mechanical cam with lash, those contacting collision noises maybe aren't noticeable.

I agree - I feel like there is a serious problem - hence this thread! lol. It's actually not too loud - a normal solid roller sound.

I get the frustration part and respect not all things go as planned

To be a repeat customer and sounds like him and pops are somewhat close I think there's a good chance for the house call the very lease

keep a cool head its only a stud or 2 and awesome job for shutting it down before carnage happened

Your spring pressures no joke so if there not a high quality type stud then I would take that into account first
Second I would look very closely on dis assembly it's your only chance to get a look at what happened before you scratch your head

Also your poly loc diameter has to be the right diameter for the roller rocker slot other wise it could shoulder out on the inside slot as in your pick

just some ideas that don't cost anything but your time

Appreciate the info...yeah just a stud or 2 now...but there s def a problem - and I'd hate for another break and a wiped motor!

Measure for rocker stud deflection and run a checker valve spring to check for binding.

Are the poly locks you are using the ones that came with the Pro Magnum rockers? The ones hat came with mine has a smaller diameter base where it attached to the pivot trunion. It should not be making those marks.

Like the ones on the right. But not cracked.

Good info Mike thanks! Yes using locks like the ones on the right...

Wait are those pressed in studs ?
Are they pinned in the head ?

Reason I'm asking is in your pic I see the rusty shank is that the part that goes into your head?

If so you may have to go to a screw in type stud not the press in type
(Or at least I would)

I also agree about the comments with the pushrod lengths being correct very critical

Screw in ARP studs...

Pretty sure that's a valve cover bolt.

This...

You should be using a stud girdle for a cam as stout as what you have. Double check the push rod length.

I use locks like these with a girdle.


Your rockers might need a smaller shank on the nut. Are the nuts you used what came with the rockers?

Jess

The stud girdle thing has been a big debate too - my friends say we need one - others say no. We asked engine builder and he said 50/50. Don't know what nuts - put together by engine builder...but I'd assume whatever came with rockers...but don't know for sure...

[grabbergreen84]

I'd be pissed, but at the engine and not the builder, if his last engine was a good one. He'll probably be pissed at that engine too, when he finds out... He'll probably want to come over and see it! Maybe a trusted supplier sent him the wrong pushrods or something.

I'd just call him up and tell him that you're having rocker studs break, and see what he says.

Sounds like a girdle might be a good idea no matter what, if the builder is really up to 50/50 undecided on it.

Can you get any kind of metallurgical analysis of the broken pieces? Maybe you all got a batch of dud studs... Even your own eyes with some good magnification could probably spot things like porosity.