Sticky Valve bucket?

[Bevelhead]

I've been rebuilding a Z1000A1 head, which I bought without any valves, springs or buckets. The head has now been skimmed, valves seats recut, and the head ceramically coated. I bought new valves and had a couple of sets of springs, collets and buckets, and picked the best to use in the head.

All was going well, valves fitted, buckets a silky slide into place... until I got to the last bucket on No 4 cylinder.. it didn't want to slide into place. So I tried a couple of other buckets and they also didn't want to fit. Everything looked ok, no dirt or visible damage, so with a little more pressure I pushed the bucket into place with my thumb.

My worry now is that when the engine is running that slightly 'sticky' bucket could cause the valve to stick open.. though with the strength of the valve spring I guess that's unlikely. Am I being paranoid? Could the head have been somehow damaged .. unseen.. that the hole for that bucket has been distorted so a bucket doesnt fit as it should??

[warren3200gt]

With the head on the bench remove the other camshaft from the head so as to not get any valve clash. Chuck a bit of oil around then rotate the camshaft with a spanner on the sprocket. You'll be able to see how that bucket behaves. If it is a bit sticky it'll soon free up. Only one winner when it comes to steel against ally wear.

[zed1015]

You are risking the bucket sticking and bending a valve.
You should remove the bucket, springs and valve.
Mark the bore with engineers blue or black marker, then fit and remove the bucket without rotating it.
Note where the bucket is tight and has rubbed the marker then polish those areas with very fine abrasive such as solvol autosol until the bucket slips in as freely as the rest..

[Bevelhead]

With the head on the bench remove the other camshaft from the head so as to not get any valve clash. Chuck a bit of oil around then rotate the camshaft with a spanner on the sprocket. You'll be able to see how that bucket behaves. If it is a bit sticky it'll soon free up. Only one winner when it comes to steel against ally wear.

I had to wait to fit the cams as a couple of the cam caps were missing their dowel pins, which I have ordered today.

[Bevelhead]

You are risking the bucket sticking and bending a valve.
You should remove the bucket, springs and valve.
Mark the bore with engineers blue or black marker, then fit and remove the bucket without rotating it.
Note where the bucket is tight and has rubbed the marker then polish those areas with very fine abrasive such as solvol autosol until the bucket slips in as freely as the rest..

Yes I think your right, will have to remove the valve and work out where the bucket is touching the sides of the bore. Is this a problem that is known in these heads?

[warren3200gt]

The buckets rotate in their bores so just polishing one point of contact will stop that from happening. You'll end up with the bucket only fitting in one position. That's why I said rotate the cam with a spanner on the sprocket. You won't bend a valve unless your an absolute animal with the spanner. Leaving the valve and spring in whilst you do it will mimick engine running forces on the bucket which will rotate the bucket as it would when running and will stop the bucket moving to far down the bore. If the bucket sticks and the spring is not strong enough to push it back up you'll be able to apply some pressure on the valve head to release it which you won't be able to do without the spring and valve fitted.

[zed1015]

The buckets rotate in their bores so just polishing one point of contact will stop that from happening. You'll end up with the bucket only fitting in one position.

NO! It is the raised spots in the bucket bore that need easing back NOT the bucket itself.

[warren3200gt]

But you don't know if it's the bucket or the bore that's out of round.
The bucket could have a tiny scratch and have a burr on the edge of it.

[zed1015]

Yes I think your right, will have to remove the valve and work out where the bucket is touching the sides of the bore. Is this a problem that is known in these heads?

Yes! but not just these heads.
I've had a few that have had the odd tight bore especially when they have had a weld repair close by or have been subject to excessive heat.
More often than not it's one on the exhaust side too.
Just to be clear - It is the raised spots in the alloy bucket bore that need easing back , NOT the bucket itself.
Mark the bore, fit the bucket and remove.
Work on the high spot then re-mark and repeat.
Bucket can go back each time in any position as it should be perfectly round which you confirmed by switching other around buckets in the same bore and the problem didn't move to another bore.

[zed1015]

But you don't know if it's the bucket or the bore that's out of round.
The bucket could have a tiny scratch and have a burr on the edge of it.

Yes! i do.
He clearly stated that a few other buckets were tried in that bore and they all were tight only in that bore.

[Al]

This has come up on here quite a bit in the past but not seen it recently. I dont know if its the same because you dont give details but i think it was generally accepted that it was frequently caused by poor repairs to cam cap threads particularly the J heads which are made from drop forged peanut butter.
The helicoils go in on a taper tapped hole and then close up nearing the bottom. If you then use a bolt that goes to the end of the thread it expands the hole sideways into the well. Other reasons i can remember; using a massive BSF bolt, which was drilled in in the absence of the locating dowel and doing both jobs, a helicoil into a helicoil, bolt snapped off in the hole and another put in on top which just rammed it down and outward and the use of a woodscrew instead of a bolt
AL

[Bevelhead]

Bit more info. I managed to remove the bucket this morning, had to use pliers to do so. Will investigate further later today. The head itself was bought with no valves etc, just its cam caps. It was one of the few I'd seen on Ebay that didn't have any broken fins.

When it arrived, I had it skimmed and the valve seat recut. When I collected the head it was wrapped in bubble wrap. Once home it sat unopened for several weeks. When I finally unwrapped the head, I was shocked to find it must have been dropped, as several fins were now broken. I had the broken fins repaired, paid for by the machine shop, and then had the head ceramically coated to match the rest of the engine.

Some of the damaged fins are closest to the sticky bucket, so I guess the shock of being dropped or the heat from the welding has caused the distortion of that bore?

Broken fins


Repaired


Empty engine, ceramically coated

[zed1015]

It's not a coincidence that the sticky bore is next to where the weld repairs were done .
On another note, Have you checked that the cams spin free in their journals with the valves out and the head on the bench.
Some of these heads can have a slight twist when in their free state which corrects when torqued down.
If one of these heads is skimmed the twist will remain on the journals when the engine is built and the cams will bind.

[Bevelhead]

Still waiting for new dowel pins for the cam caps, so haven't been able to fit the cams yet. On a brighter note, I removed the valve and spent ten minutes carefully cleaning up the walls of the bore using 600 wet n dry, followed by 800 then Autosol. I wasn't expecting much difference, but now the bucket slid down into its bore no problem. I think the issue might have been a burr on the very lip of the bore, which had now been removed.

Panic over.

Thanks for all your help.