Camshaft Thrust Surface Axial Runout

[VWLover77]

My new Type IV stock hydraulic camshaft "ate" the thrust bearing, opening the endplay from 0.003" to 0.010" in a few hundred miles. This was after polishing the thrust surfaces to remove the Parkerizing that was on them.

I measured the axial runout (fore and aft) on the camshaft thrust surfaces and found 0.002" on each side. This seems excessive given a camshaft endplay range of 0.0016" to 0.004".

How much is too much?

I'm guessing that at speed, the runout is pushing the cam back and forth rapidly in the thrust bearing, destroying the bearing thrust surface.

Thoughts?
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[timvw7476]

was it the Parkerizing on the camshaft ?? (that was polished off?)
I've run a camshaft that had welded up lobes & Parkerizing & left it be &
run for an admirable length of time. The deviation number stamped on the
backside of the factory cam gear comes into play as far as lash is concerned.
A O marked (neutral) gear can do bad things if your original unit was a -5 or
a 7 or who knows what. The Parkerizing is a perishable coating, I'd let it get pulled off by friction, YMMV.
EDIT: there is a 'bind test', when the cases are separated, rotating the crank &
cam in the case half. If the camshaft attempts to lift out of the bearing shells, or there is a bind, the cam gear gets changed to a different number.

[VWLover77]

The Parkerizing that I polished off was a rough "overspray" on the thrust surfaces of the camshaft that ride against the bearing. I thought that roughness against the soft bearing material was a bad idea.

I did the cam gear tests before assembling the engine. No binding, no lifting of the cam when the crank was rotated backwards.
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[orwell84]

What kind of oil pump are you using?

[VWLover77]

I think I know where you're going with the oil pump question. When I built the engine, I triple checked that the oil pump drive tang was floating in the cam slot axially and not touching or exerting thrust force on the camshaft.

It's a modified Type 3 Schadek oil pump that I bought from European Motorworks.
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[RalphWiggam]

Not surprised. The stories of bad thrust surfaces on type 4 cams are increasing rapidly. Happened to me as well and I did the best I could to correct the errors during the build up.

Somebody is doing a shit job on final qc of cams in the past couple years. If they are even checking them at all.

They are costing people a ton of money and ruining a bunch of already hard to find cases and parts.

[orwell84]

[germansupplyscott]

[VWLover77]

[orwell84]

So you are measuring endplay like this and not the runout on the thrust surface, if I understand correctly.

If you are getting .002" of total movement fore and aft than endplay would seem spot on. If you you are getting .002" of runout on the thrust surface that would seem like a lot.

Are you measuring this on a new thrust bearing? I think you are saying that you are getting this runout with the cam thrust surface pushed up against the bearing thrust surface and are describing the combined runout (uneveness of bearing thrust surface + whatever runout of the cam thrust surface).

Try getting a measurement of the thrust surface runout by itself.

[Starbucket]

That looks like .0015" to me.

[VWLover77]

[skills@eurocarsplus]

it's shit like this that makes me never want to jump inside another aircooled again. even when you do your best, it still isn't good enough
_________________

[Starbucket]

Check the center journal and see if the cam is warped when you rotate and have a helper hold a leather belt and apply downward pressure on the front and back journals while you rotate the cam.

[germansupplyscott]

I don't think the method is funny, it's clever but I am still not sure it's accurate enough for what you're trying to do. But there definitely seems to be measurable runout.

The next question would be a 2-parter.

Why did you suspect an issue with the thrust surface of the cam bearing (you must have noticed something or you wouldn't have take the engine apart) and what kind of bearings were used?
_________________
SL

[raygreenwood]

[VWLover77]

True confessions..... The first time this camshaft went into the engine, I made two big newbie mistakes. The first was assuming the Wilson book was comprehensive. It's not. There is NOTHING in the engine assembly chapter about checking camshaft endplay, and I didn't. The second was not inspecting the camshaft thrust surfaces. Both had "parkerizing" overspray on them that I did not see. Within a couple of hundred miles, the engine was making loud knocking noises at idle. I pulled the engine and found excessive camshaft endplay and the thrust bearing "eaten".

I bought new Mahle cam bearings, cleaned up the cam thrust surfaces to remove the parkerizing, and learned about checking camshaft endplay thanks to this forum. The engine went back together with 0.003" of camshaft endplay, smooth, shiny cam thrust surfaces,..........and a number 3 main bearing that wasn't properly seated on its dowel pin. It went a couple of hundred miles before it seized.

Before the seizure, it seemed to be getting noisy again at idle. I checked the camshaft endplay after removing the engine and oil pump and found it at 0.010" and the thrust bearing eaten again.

So, as I'm working through the rebuild yet again (with a reground crank and freshly align-bored case), I'm especially worried about the cam thrust bearing which led me to do this check. I'm thinking this runout is making the cam bounce back and forth at high speed and eating away the bearing thrust surfaces.

I measured the cam radial runout in a case half at each journal with its bearing removed and the other two installed. It appears to be perfectly straight - virtually no indicator movement at all on any journal as the cam is rotated.
_________________
Don

1978 Westy
1971 Super Beetle Convertible


"If more of us valued food and cheer and song above hoarded gold, it would be a merrier world." - J.R.R. Tolkien

[orwell84]

Ok, I get it. I was overthinking it. I measured the runout of the thrust faces the same way, though with a crappier gauge. I got goose eggs. You shouldn’t be getting runout or barely any.

[VWLover77]

[orwell84]

I went through the same thing with the crank from my old engine...removed the center main and slapped a dial gauge on it. It went bumpity bump, out .002”. I thought this can’t be. It must be my hokey assed measuring set up so I set it up better, same thing, bought some v blocks and sure enough, same measurement. The #1 bearing was out .0035” when the center main was supported. I took it to a machinist and asked him to measure it on centers. Say it ain’t so, I said. He got pretty close to the same measurements.

So you are probably right. It’s off somehow. I would wring my hands less replacing a cam than a crank.