Technical Engine builders: Why is my new 322 breaking rockers?

Ya' know , I'm 68 years old and have worked on engines since I can't remember and I've never seen a nailhead valvetrain , so thanks , got to see sumpthin' that I've never seen ... cool
dave

 

Me too Fast

Used to watch Ivo run his Buick powered cars but never saw inside of one of those ' Nail Heads '

 

Im gonna say you have to heavy of springs those angles look harsh for the push tube to get leverage for springs or valve stems are to tall look at it from a leverage veiw

 

Hey Roady

What did you ever figure out on your Nailhead valve train ?

 

On my way home. I have an 8 hour drive ahead of me. Then some shop time.

 

Thanks to everyone that has contributed. Craig thanks for contacting Centerville, he and I have been trading emails as well to see if I get to the source.


I started on the left bank where I broke an exhaust rocker first.
I verified the oiling location of the shaft assembly is correct.
I did notice a few rocker tips are worm more on one side versus the other. I presume this is due to the fact we did not re-bush the rockers, and due to the offset the rockers twist while rotating on the shaft

[

This is a picture of the replaced rocker. There is a nick you can see but I cannot detect if this is from touching the spring retainer. There is no evidence of any hitting or damage on the three broke rocker.



Here is a pic of the broken rockers underside.



And a pic of the break. I can see a few voids, but not sure it would be the root cause.




Here is one of the broken intakes. Note a that this is a different failure location, and the big casting void around the oiling hole



Here is the other broken intake. Similar failure to the exhaust rocker.



Here's a close up of the wear pattern, wear you can see some uneven wear. Presumably from a loose fit on the shaft or perhaps when the tips were resurfaced.



So far no single smoking gun.

 

So I decided to replace the broken exhaust valve spring.



I made a cylinder pressurizer. The plug end came from a cheap compression tester that had a bad gauge.


I Removed the broken spring. This gave me a chance to check guide height. This matches another set of original heads I have.



I also measured to the top of the valve stem. I'm not sure what this should measure. Let me know if you know a dimension.



I stuck a piece of hose on the valve and released the pressure. It spins nice throughout the range of motion, and is not bent. I cannot detect if their is .0015 clearance or not. I didn't detect or see any galling.



Here's the top side of the retainer. No signs of damage from hitting the rocker.



Here's the other side with no signs of hitting the guide.




I verified the wire diameter of the falcon supplied spring matches the sealed power replacement I got from rock auto.



So I put a new inner and outer spring in. Which is where I am at as I type this.

 

Here is the underside of the retainer.


And the part numbers of the inner spring and outer spring from rock auto.

 

Found the cam specs. This is actually a new cam, not made from a core. Pretty mild grind.

 

The only thing that would cause this is if the rocker is being pushed beyond the point of max spring compression thus making the spring a block instead of a spring. You could try loosening up the adjustments on the pushrods to where the slack is just taken out. Maybe the cam has tooooo much lift for this application???

 

I need to get another set of intake gaskets, but I'm thinking I should double check the push rod length, double check for any spring bind.

 

Good luck!!

 

It really is worth looking at the rocker angles at full open, like the above post leads to.

Especially after seeing the very last full close up of a single rocker in post 36. That is one odd break on that one, where it blew the cup outwards?

If you hold a good rocker in your hand and wonder where it "should" break with coil bind, wouldn't it break on the weaker longer side? It seems like what was said; "pushing away", rather than rotating.

.

 

The exhaust guide clearance should be 2.5 and INTAKE is 1.5 with new SS valves... The valve spring installed height is 1.5 on the 53-58 nailhead and 1.6 on the 59-66. The difference is in the valve lock location which is 1.00 higher on the later valves (all engine stem height is 1.540) . Because of this the early engines can get coil bind much easier. Buick made different valve springs for the 53-56 and the 59-66 but now the aftermarket uses the later spring on all nailhead's. This boosts the spring presser and can cause coil bind with a high lift cam. I notice the cam info said nothing about the 53-55 and 56 and later lifter being different. Russ

 

You really need to put a indicator on the retainer and measure what your cam lift is at the valve, then measure what the distance from the top of the oil seal is to the retainer & the space from the head to the retainer for your installed height

Try to find someone that has a spring checker, then you will know what your installed seat pressure is and at open too and how much extra travel your spring has to coil bind as I think that somehow that is your problem

One other way to do a quickie check is to put a indicator on a retainer at full lift and use a pry bar and push the rocker arm down to open the valve to coil bind and measure how much travel you have past full lift

You need a minimum of at least .050 to coil bind

There is a answer there someware just need to do some more checking

Too bad you live so far away you could use mine and we could find out what the heck is going on

Don

 

After I replaced the spring and re-installed the rocker shaft assembly checked the push rods on both sides with a finger spin test. Two on the right bank seemed quite loose (almost dangerously loose). I started the car with valve covers off and let it run a few minutes. I randomly stuck a .010 feeler gauge between the springs with no binding, and also could check a few rocker to valve spring retainers with a feel gauge with adequate clearance.

When I shut it off the loose pushrods tightened up like the lifters had pumped up.

Russ Martin warned me of bad Chinese lifters. I'm wondering what the failure mode was / is (draining down or collapsing) Could a lifter drain back enough (while sitting) that upon start up it would lose contact with the rocker and come out of the cup and on the return stroke push out of the pocket, which would bind the spring and break a rocker? The first exhaust broke on cold start up.
Two of my pics show some marks around the rocker socket..could this be from the push rod?

 

It sounds like there is no preload adjustment on the lifters

 

That's plausible. I steer clear of juice lifters as a rule, but yes, I would say that could cause the broken rockers.

 

and as far as checking installed height, you need to install the retainer and split locks, and measure from the bottom side of the outer "step" on the retainer to the spring seat with a telescoping gauge, then measure it with your calipers. Or, if your all Mr fancy pants, you can use a valve spring mic.

telescoping gauge


valve spring micrometer

 

If the retainer was hitting the top of the guide, I would expect to see witness marks on the bottom of the retainers, I don't. Are the tops of the valve stem seals damaged?

 

I can't really help with your problem, but, like someone else already said, this is the first time I've seen the actual "insides" of a nailhead Buick. There is an awful lot of "stressed" geometry from Buick engineers in that valve train; lots of "angles" compared to other OHV/V-8 engines. But, very clean and obviously great attention to detail on your part! I hope you get this sorted out. I am Butch/56sedandelivery.

 

I'm sure you already know Buick used two different length push rods and lifters (322-264) during these years, my engine builder used the wrong lifters in my 322 and the valves wouldn't close, no compression, these things sometimes get mixed up by builders/suppliers.

 

On the bleed down; I have a 1953 Olds 303 that has old lifters that completly bleed down when I shut the motor off. You can watch all the valves completely close within 3 or 5 seconds after shut off. On restart, they seem to pump back up quickly, and it never has had a pushrod jump....but the Olds is nothing like the Buick rocker angles.

on possible spring bind, or retainer bind; if the intakes and exhausts use the same springs and retainers?..then with the greater lift of the exhaust lobes, why hasn't it broken just the exhausts?

I sometimes do untechnical (hack) things when chasing a strange problem. If it was here, and if the guys are leaning towards coil bind or retainer clearance bind, ...I'd get my huge channel locks and set a few rockers at full lift, then grab the damn rocker and see if it can depress the valve more than the cam is. Yes, it might leave a mark on the rocker material...but it would be a fast, but crude way to see.
.

 

I would figure out and FIX it before I started it again!! I would have had that thing apart long ago. Sorry JMO. Lippy

 

I totally agree, Nailheads are not cheap to rebuild to begin with. Something is not right, Rockers do not break for no reason. Take it apart and get to the cause before something really bad & expensive happens.
Good luck on getting it fixed. The 1956 322" I had in my 53 F100 was a great Engine, they are a real neat piece and run as good as they look.

 

You know, if you had a flathead in that thing, you wouldn't be having all these problems. Rocker arms...bwahaha!

 

Frustrating!

 

If the stem height was set too low , the rocker would have to "over-rotate' making the pushrod push to far "outboard" on the short side of the rocker...
dave
May be a place for lash caps ??

 

Easy to check coil bind, with the valve full open, you should still have at least .060 clearance between coils. Check that and if you do, you can eliminate it right off the bat.

 

F.G. I agree completely agree with this, but I would be worried about getting a "false" reading if the lifters have bled down at all. How would we know for sure? This issue is puzzling to say the least.