Broken rocker stud. wrong length pushrods?

[rdc767]

I am a total novice. This is my first engne build. The engine ran well for about 200 miles. But something gone a miss.

Its a 1984 windsor 351 stoked out a bit to 383 with a street/strip cam .520 lift with hydraulic lifters. The block and heads have been decked. The heads are procoms aluminium with pushrod guild plates.

I think I screw up the pushrod length. When installing the pushrods I checked them by turned the motor over to check the wear pattern . It looked good. Right in the center. The pushrods are COMP Cams High Energy Pushrods, High Energy, Steel, 5/ 16 in. Diameter, 8.234 in. Length


Today the number 7 cylinder rocker stud broke. Looking at the pushrod it was rubbing up against the head near the stud. ARE the pushrods too long? Should I have bought harden pushrods?


After looking back I see the stock length is Windsor engine; 8.182"



You can see the wear pattern on the one valve stem.

[lineslinger]

It takes a lot of force to snap off the stud as shown in your photo.
I guess it possible the stud itself is at fault but I have doubts about that.
Something is obviously binding or an out of sequence opposing force had to come into play for that stud to snap.
The curious part is the push rod does not appear bent although the photo does not show the complete length of the rod. Looking at the ware on the push rod from rubbing against the guide hole (which it should not be doing) in the head.
The push rod might have gotten hung up/stuck on the newly worn edge (at least it looks like a sharp edge) at the top of the guide hole and forced the stud to snap with an out of time/sequence lift. One could speculate the rocker arm might go before a valve train stud though. Just one quick guess.
Some mods to assure clear push rod movement on all cylinders are needed, obviously, along with confirming the push rod length being correct.
Too bad but in a way you may have gotten lucky that the stud let go instead of a more involved and expensive "injury".

[rdc767]

Too bad but in a way you may have gotten lucky that the stud let go instead of a more involved and expensive "injury".

I was thinking about getting the expensive ARP studs but I am glad the valve closed by the stud breaking before the piston bent the valve. Just pushing down by hand on the valve spring it does moves a bit. At least the stem near the spring is not binding.

The push rod might have gotten hung up/stuck on the newly worn edge (at least it looks like a sharp edge) at the top of the guide hole and forced the stud to snap with an out of time/sequence lift.

The intake pushrod was bent but it did come out. But the exhaust pushrod where the stud was broken was straight. Makes me wonder what happen first?

[bobcowan]

The wear pattern on the valve tip looks pretty close to perfect.

If the push rod is rubbing on the head, that's the problem. As it goes up, it hits the head, and pushes the rocker arm foreward. The stud is not really designed for lateral strength, and it snapped.

Since you're using an offshore knock off head, I would think the the hardware on them would be suspect.

You need to remove the heads to grind that area for clearance. That is a common problem/issue with any head, and one of the areas that needs to be checked during assembly. I would also replace all of the studs with good ARP studs. Be sure and use thread sealant during installation. And I would replace all of the push rods. The rocker arms, guide plates, springs, and valves should be fine.

Since this is your first engine build, don't beat yourself up over it. Good decisions come from experiance. Experiance comes from bad decisions. This mistake won't cost you that much. Some of the mistakes I'v made..........

[zrayr]

anytime you have guide plates, you need hardened push rods. As far breaking a rocker stud, I had one break after a new rebuild, it happens, and sometimes nothing else "caused" it. Could've just been a defective rocker stud.

Z. Ray

[DAVID GAGNARD]

I would also get rid of those pushrods and get a set of one-peice pushrods......After about 2,000 miles my engine developed a miss and after pulling the valve covers, I found 3 pushrods DID NOT have the little pressed-in balls on the ends anymore!!!!!!!!!!!!!! Since then, I've never trusted those type pushrods and will only use one-piece pushrods...........

David

[Rick Parker]

How many threads are captured by the adjusting nuts? I would recheck the length of your pushrods. It looks as if they are too long causing the static position of the rocker arm to be too high on the end with the pushrod. As the cam raises the rocker arm up, and it starts to "Rock", the arc that the upper cup travels through causes the pushrod to move in the guide plate toward the stud. As the limit of travel was reached (as it pivoted) and the cam continued to force the rocker arm, it forced the pushrod into the bottom of the slot as it was bending it over the edge of the guide plate. It reached the travel limit and with the stud in severe tension it popped. Get the ARP studs and check the pushrods.

This situation gets worse if you are using 1.7 ratio rocker arms.

[vector1]

when you checked for pushrod height you didn't compress the hyd lifter in anyway?

hyd flat tappet doesn't have that much spring press, what are your spring pressures by the way?

i'm thinking something is amiss intereference wise.

valve tip wear looks good.

[FuzzyDiceRide]

Originally Posted by vector1

when you checked for pushrod height you didn't compress the hyd lifter in anyway?

hyd flat tappet doesn't have that much spring press, what are your spring pressures by the way?

i'm thinking something is amiss intereference wise.

valve tip wear looks good.

Good question Victor, I was wondering if he used a solid lifter
or a shimmed hydraulic lifter that wouldn't collapse when he did
his measurement? However, his valve stem wear looks good. It
has been a while since I built and engine and this post caught
my eye and I checked and doubled checked and hope I don't
have this gentlemans problem with my engine. Something is
definitely binding. I wonder about the brand heads he has too.
The valve stem wear pattern and the fact he drove it 2000 miles
makes me think his valve geometry is not too far off ?? So ,what
about the quality of the studs and the rubbing pushrods against
the head or guide plate too?.....Good luck sir !! Let us know
what it took to get your problem fixed too please . Mike

[jbuchert]

My guess was not enough thread engagement. A lot of stress was applied to only a small portion or tip of the stud. That combined with the rocking motion and high spring rate it was only a matter of time.

[Gaz64]

I agree with the other boys comments, you definately have a binding issue, be it pushrod to head, pushrod to guideplate, coil bind, retainer to guide etc.

If one has done this, the fault will be with the other 15 as well.

If that pattern on your valve stems is a wear mark, I'd be concerned and fitting a set of hardened lash caps, roller rocker wheels are harder than valve stems.
You'll be resetting your lifter preload more often until you discover the valve stems peened over.

When you built the engine, did you use a solid lifter for rocker geometry check?
Did you rotate the engine while checking the clearances within the rocker itself, to stud, to pushrod, to retainer, retainer to guide/seal, pushrod to head, pushrod to guideplate?
Everyone of these clearances is critical, if one of these is too small or zero, the inevitable will occur.

You must run hardened pushrods with hardened guideplates.

[rdc767]

Thanks guys for the advice. I was kinda depressed yesterday thank you for the encouragement. This forum is great!



I did some googling on Pro comp heads. I gather they are Chinese junk. You get what pay for. I'm not the only one with rubbing pushrods. I really couldn't gather how to fix it.

so far.

1. Pushrods to long
2 clearence the guides (file a bit bigger)
3 harden push rods.
4. clearend the pushrod guide hole.


anything else let me know


I did turn the motor over on the stand when building it. I was manly looking at the wear on the stem tip that it was centered. I set the rocker tension with the manifold off. I locked the rocker as the pushrod just started to push the hydraulic lifter spring down being careful not to bottom it out.



I am was thinking the pushrods are to long except. I found the rocker is striking the stud after the cam comes off the lobe. There are wear marks on the back of the studs. If I used shorter pushrods would this make it worse?



Here is a picture of the broken stud. I would say the nut uses half the stud threads. The broken part was about 3 thread up in the nut. I was able to use a screw driver to work it out. Being that far out I could see it woobling a bit.




heads look good. Is this much carbon o.k for 200 miles
I am kind of concered about the engine temp. It's been cool here and most times the engine runs between 150 and 170f. I drilled so air relief holes in the thermostat. Maybe too big?

[Gaz64]

Can we have a pic of the bottom of the rocker?

Who makes the rockers?

The stud broke because the rocker has been striking it on the backstroke.

To me, it looks like the pushrods are too short, but it seems you have not enough posilock thread engagement on the rocker stud.

So the only other thing left is the rockers aren't capable of over .500 valve lift.

Shorter pushrods is not the answer.

You do have many issues with your valvetrain, I'd be onto your supplier for a remedy and some
answers.

200 miles, carb too rich.

[rdc767]

Thanks guys
The more I look on the web and your posting I am learning alot. I don't think the rocker is rolling back and striking the bottom of the stud. There are no wear marks on the roller rockers.

I found this thread.

http://www.fordmuscle.com/forums/all...plate-fix.html

With not having harden pushrods and a mis aligned pushrod guides caused a bind and snaped the stud.

I found isky adjustable guides at summit. I think the rest of the part list should do it.


--------------------------------------------------------------------------------

AFR-6104 Isky 5/16" Adjustable Guide Plates ; Qty: 1 set $48.95 $48.95
·This part is temporarily out of stock, but you can order it now. Tentative ship date: 4/16/2009, if your order is placed today.

ARP-134-7101 Rocker Arm Studs, High Performance, 3/8-24 in. Thread, 1.75 in. Effective Stud Length, Chevy, Small Block, Kit $37.95 $37.95

FEL-8548PT-2 Head Gasket, PermaTorqueMLS, 4.100 in. Bore, Ford, 260/289/302/351W, Each $16.69 $16.69

FPP-1262 Gaskets, Intake, Composite, Printoseal, 2.10 in. x 1.28 in. Port, .060 in. Thick, Ford, 260/289/302/351W, Set $21.95 $21.95

FPP-1486 Exhaust Gaskets, Header, Steel Core Laminate, Dual Bolt Pattern Splayed Port, Ford, Small Block, Set $33.69 $33.69

LUN-7078-16 PUSHRODS $115.95 $115.95

[Dwight]

Buy a adjustable push rod and check the length after you get all your parts in. I had a pair of Pro Comp heads and did not check the push rod length. After I wore out the valve guides I borrowed an adjustable push rod and checked the length. I was a 1/10" short. Sold the heads, bought KC heads and I am in the process of putting my motor back together. I was scared of the possibly that the Pro Comp heads had Chinese bolts and springs.

Dwight

The Keith Craft / Brodix heads are a work of art, I hate to cover them up.


See ya'll in London in June

P.S. I used the laminated aluminum header gaskets. Cost about $50 but they don't leak.

[CHANMADD]

The rocker nut should sit in the machined recess in the pivot shaft stud hole.
Also the rods do have to be the hardened variety if you use any type of guideplate. The wear marks on the top of the valve indicate to me that the pushrods could be a fraction shorter to move that wear mark exactly in the middle of the stem.. But if you have cheap studs they are going to break.
John

[Gaz64]

Is it possible you have fitted that pair of rockers with the rocker trunnions upside down?

That may explain the mark on the stud, the trunnion was moving and flexing the stud in the process.
The trunnion has a flat recess for the posilock to seat against.

Your "rocker strike" or contact mark on the valve stem favours the stud side which means the pushrods are too long.

[DAVID GAGNARD]

Originally Posted by Gaz64

Is it possible you have fitted that pair of rockers with the rocker trunnions upside down?

That may explain the mark on the stud, the trunnion was moving and flexing the stud in the process.
The trunnion has a flat recess for the posilock to seat against.

Your "rocker strike" or contact mark on the valve stem favours the stud side which means the pushrods are too long.

That was going to be my question. When installing the roller rocker arms, look "inside" at the part that goes over the rocker stud, one side is flat and the opposite side is rounded. The rounded side goes down and the flat side up. The poly lock rests on the flat machined surface of the rocker arm. You may have had this one upside down... The wear on the pushrods from the guide plates indicates either they are not hardened pushrods or very cheaply made pushrods.

I would install all new rocker studs,a good set of hardened pushrods and check and re-check all your rocker arms for any damage.

David

[rdc767]

The flat side of the roller rocker tunion was up for the poly lock. I can see how this could happen.

The arp studs are longer 1.75 compared to 1.5 for the stock... With shorter pushrods should bring the rocker lower on the stud.

I did wear check with a felt marker on a few location and it looked ok..... Next will be stock legnth.

Most of the wear marks are centered. But some are on the sides. Just from researching Pro comp heads on different forums there are reports that the pushrod guides are off and the studs are off centered too.(cheap machining in china) Looking at the guides you can see it. Isky make a adjustable guides I will try. The rockers look in good shape with no stress marks.

thanks again for the thoughts.
Ron

[Rick Parker]

Ron: The Isky adjustable guide plates are a very good and often overlooked idea. They can be carefully tack welded (Tig) after final adjustment and alignment is achieved to eliminate future movement.
Take your time to get the roller directly centered over the valve stem. Recheck after tightening the stud on the guide plates.
Don't be so quick to denigrate the heads you have. They are marketed at a very attractive price point. Yes they may need to be "touched up" but just treat them as castings and add good hardware, pay attention to details and you'll have a very good set. Many that aren't aware of it, have their pushrods and rocker tips misaligned on 289, 302, & 351's. It is very common. That was the purpose of the shaft mounted rockers being developed along with eliminating the side to side flex in the stud as the valve opening forces are exerted upon it. Cycle the engine and look at the areas where the pushrod gets close to the head itself in the slot. Be certain they do not "bottom out" in the slot (doubt they will) unless you are using a high ratio rocker arm (1.7+). Also keep an eye on the area where the spring is under the rocker arm close to the stud sometimes the rocker will hit on the spring retainer.

You're on the right track....just keep an eye on all the details.