[P@blo]

Originally Posted by Jimbobeast

Unfortunately Yow's Machine shop closed their doors 12 years ago and Roy, Johnny and Dave Yow have long since "shuffled off this mortal coil". That's from Hamlet. It's a play. By Shakespeare. It means they're dead. In their defense they did the machine work on 5 other GTO engines for me, including a RAIV, without problems.
I do love the looks of an Orbit Orange/Black Top '70 Judge convertible, even in the garage. Always have.

Hamlet reminds me of grade 10 or 11. I can't remember now. Nice car there!

[OG68]

English Lit. Sophomore year. ZZZZZ

[Jimbobeast]

I am at my wit's end.*
To recap, I'm building a stock 1970 GTO RAIV engine (614 heads, ww block, etc).* The heads were originally assembled by a local "Pontiac" machine shop 10+ years ago but final assembly was done 1 year ago.*
It had a RAIV replacement cam and Comp Cam roller tip rockers.* Everything*else stock.The machine shop messed up and did not machine the valve stem bosses, so the inner aftermarket springs did not seat and sat too high, creating too much pressure.* On first start up it broke a few pushrods at the top ball.* I did not know the springs were too high and thought maybe I over tightened the rocker nuts.* Same thing happened with pushrod set #2 (all 9.2", 11/32) obviously.*
Out came the engine, off came the heads and I had the bosses machined.* Heads and engine reassembled with Butler Performance *RAIV kit (still using the 1.65 Comp Cams roller rockers), this time with poly lock rocker nuts.* Valves were measured and lapped in, correct original valves.* Valve springs installed height was 1.84" (only one needed a tiny shim) and seat pressure measured between 118 and 120 lbs.I rechecked this twice.**The roller tips on all valves sit squarely on the middle of the valve stem top.* Geometry looks perfect.* I used the Butler RAIV equivalent cam and lifters and pushrods.* All pushrods mic'd just for fun and dead*on.* Engine primed and each valve adjusted to zero lash plus 1/2 turn.* *ZDDP added, new filter, engine fired up and run at 2000 RPM for 15 minutes and shut off when it began to get a bit noisy.*
I took the valve covers off and there are two broken pushrods.* Same type of break as all the others, at the rocker end, ball is pushed down into the shaft, causing it to flare out.What am I doing wrong?* What else can I check?* Are these modern pushrods prone to failure?* I checked for spring bind but there is plenty of clearance between coils.* I am very frustrated.* I hope someone out there can provide some insight.**

[steve25]

are these broken parts taking place on the same valves as the first failure?

[johnta1]

!st thing is check that the push rods are not hitting/rubbing anything all through its travel up and down. (pushrod guide should just be wider than pushrod and the closed end of the guide should not hit the push rod at all)

2nd thing is check that the rockers are not hitting /rubbing anything except the push rod cavity for the push rod ball and the end of roller does not touch anything except the valve tip. (roller doesn't run off end of tip of valve, etc)

If it was mine I probably would have bought chromoly push rods that has no balls on it.

[steve25]

John has a good point here.
The original rA4 motors had 11/32” diameter push rods to handle the open pressure.

If your using 5/16” factory push rods you could be finding out there limit.

[turbo69bird]

Did the machine shop assemble this engine with the inner springs binding? If so I’d pull that whole engine apart and check EVERYTHING. If they couldn’t catch that on assembly they shouldn’t be in the machine shop business .
That being said . Take the good push rods from another cyl and put them together on those two cylinders and crank the engine over and watch the push rods and rockers for it to destroy the push rods something is big time wrong I’d expect you’d be able to see it.

I feel for you my friend sucks when stuff like this creeps up.
But I don’t wanna see you throw a rod because the machine shop didn’t dot its I s and cross its T s. As much as it sucks at this point, id be tearing that thing down completely and starting over, Because I wouldn’t trust their work

[b-man]

Rocker arm slots hitting the rocker studs at full lift?

Are you still using the Comp roller tip arms or did you switch to Comp full roller rockers?

[chuckies76ta]

Sounds like those pushrods must be binding in the heads. Something is binding. Like mentioned put it together spin it over by hand and check valve train. I have a set of 5/16" x .116 one piece Smith brothers pushrods here if interested. They have been used for a season here. Still perfect shape. The length is 9.300" I also have a set of full PRW roller rockers 1.5 Ratio with poly locks you could try. Nothing wrong with them.
Something you could try is to install just the pushrods and rockers on the cylinders that are causing the breakage. Leave all the other pushrods and rockers off. Remove the spark plugs to let the combustion air out of the cylinders while you turn it over. Check them for any visible binding.

[Jimbobeast]

Originally Posted by steve25

are these broken parts taking place on the same valves as the first failure?

No, different valves.

[Jimbobeast]

Originally Posted by johnta1

!st thing is check that the push rods are not hitting/rubbing anything all through its travel up and down. (pushrod guide should just be wider than pushrod and the closed end of the guide should not hit the push rod at all)

2nd thing is check that the rockers are not hitting /rubbing anything except the push rod cavity for the push rod ball and the end of roller does not touch anything except the valve tip. (roller doesn't run off end of tip of valve, etc)

If it was mine I probably would have bought chromoly push rods that has no balls on it.

No push rod binding, travel is not impeded in any way. Chromoly rods are ordered

[steve25]

What retainers are being used?

Have any of the valve guides been replaced with 1/2” OD guides?
If so have you checked for retainer to guide / seal clearance?

[65 Lamnas]

If you haven't already, remove the valve springs and pushrods from the 2 cylinders that failed. There's got to be some witness marks from some components making contact where they shouldn't. Looks at the retainer bottoms to see if they've been contacting the tops of the guides....there will be contact marks. Look at the tops of the guides for witness marks. Inspect the springs for coil bind or some other type of mechanical interference. Inspect the pushrods to see if there are witness marks on them. Look at the slots under the balls on the rocker arms. Look at the studs. Are the rockers making contact on the outer circumference of the retainers? There will be marks on the rockers and retainers.

[Jimbobeast]

Originally Posted by steve25

John has a good point here.
The original rA4 motors had 11/32” diameter push rods to handle the open pressure.

If your using 5/16” factory push rods you could be finding out there limit.

As stated above, all 11/32"

[Jimbobeast]

Originally Posted by steve25

What retainers are being used?

Have any of the valve guides been replaced with 1/2” OD guides?
If so have you checked for retainer to guide / seal clearance?

Retainers were part of the Butler Performance kit for the RAIV.
I don't recall the brand. No replacement 1/2" guides.

[Jimbobeast]

Could the Comp Cams 1.65 roller tip rockers somehow be binding somewhere? The valves are perfect, the spring tension is perfect, new guides/seals/keeper, new cam and lifters and pushrods. The only thing that stayed the same were the rockers, with the same reselt - broken pushrods and always at the rocker end.

[steve25]

As I think posted earlier by someone, if the rockers are not fully rollerized and you just have those roller tip rockers then the rocker stud slot in some of them might not be the same length in some of them which could make for your issue.

I would check this out very carefully, and in fact if I had stock 1.5 rockers sitting around I would be really tempted when you get the new pushrods to start off with those on the motor to see what happens.

[65 Lamnas]

Originally Posted by Jimbobeast

Could the Comp Cams 1.65 roller tip rockers somehow be binding somewhere? The valves are perfect, the spring tension is perfect, new guides/seals/keeper, new cam and lifters and pushrods. The only thing that stayed the same were the rockers, with the same reselt - broken pushrods and always at the rocker end.

You have some type of mechanical interference going on. Doesn't matter if the parts are "new" or not, or were used the last time or not.

I think you're approaching the troubleshooting and diagnosis incorrectly by comparing what's different this time vs. last time. None of that really matters if there's contact between parts where there shouldn't be.

It's not a static situation, it's dynamic so parts are moving around during operation. If you're unable to duplicate the movement of the valve train components to observe what's happening, then you're going to have to disassemble things and look for witness marks and wear patterns for signs of contact. It's ALREADY been suggested that you look at the rockers and the slots and the studs. Seems like a good place to start, along with the rocker bodies contacting the retainers.

[Jimbobeast]

I can't see any witness marks on the rockers, valve tips or even the broken pushrods or rocker balls. In comparison of these Comp Cam roller tip 1.65 rockers to stock stamped steel 1.5 rockers I notice the cup in the rocker that holds the pushrod ball is much deeper on the aftermarket units. All the previous pushrod failures have occurred just above the pushrod guide plate (most just had the ball pushed into the shaft and did not fracture yet). My thinking now is that the aftermarket rockers are causing the pushrods to bind on the guideplates at full lift. This is a RAIV head, so no interference with 11/32 rods or 1.65 rockers should occur, but these are 20+ year old Comp Cam roller tips. Maybe their currrent units are better? So far I have checked 3 pushrods (2 broken) without any obvious witness marks along the shaft at the pushrod guide plate level or along the guide plates themselves. Clearance is tight on the closed end of the guideplate but I'll have to observe throught full travel. This seems to me to be the most logical reason for 3 sets of pushrods failing in exactly the same way although I understand from all the comments above that many variable can exist. The ONLY constant in the 3 failures has been the rockers and the guideplates. I appreciate all the comments and advice.

[steve25]

There is a tiny bit of play to the guide plate position when the studs are not locked down on it.
Why just for S & G don’t you loosen all your rocker studs up and push them as far as they will go over to exh side of the head.
Then lock down the two end studs on each plate to hold it there and tighten down the center two studs.

Torque is 55 lb.