worn cam, clatter

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MD
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Re: worn cam, clatter

Post by MD » Mon Dec 13, 2010 12:17 am

Something od here.
If its the wrong oil, it would affect all lobes the same.
Both lobes share the same oil well, why aren't they both worn the same?
Why is there not (or is there)the same amount of wear on the cam bucket face if it is a lack of lubrication between the cam lobe and the bucket face? At that rate the bucket top would have a hole in it.
Why is there no sign of heat?
How nuch crap is in the sump stuck to the magnetic plug?

I think somebody has fitted the wrong(read dudded)cams.It's the only thing that makes sense.
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Re: worn cam, clatter

Post by gran turismo » Mon Dec 13, 2010 11:20 am

I would not try to crank the motor with the cam out. If the pulley comes off then you will bend the valves on the other bank.

I think a better way to do it would be to remove the timing belt, take off the dist. cap, rotor, and dust cap and turn the oil pump with a drill motor chucked up to the dist. shaft.

Maybe there is a better way via the distributor/oil pump drive pulley but this is how I am thinking of doing it when I oil up my new motor.

What does the surface of the cam followers look like? If the followers are pitted it will take out the cam lobe fairly quickly. I always inspect the exhaust followers (with a magnifying glass) at every valve adjustment and replace at the first sign of pitting (and I clean out all of the little oil sumps in the head).
Last edited by gran turismo on Mon Dec 13, 2010 6:31 pm, edited 1 time in total.
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Re: worn cam, clatter

Post by ghnl » Mon Dec 13, 2010 6:15 pm

gran turismo wrote:turn the oil pump with a drill motor chucked up to the dist. shaft.
Can one do it that way with the Alfa V6?
What does the surface of the cam followers look like?
All the cam followers of the obviously worn lobes look bad - pitted. The unworn/less worn lobes have cam followers that look good - smooth & shiney. I did not check if they are flattened out or slightly convex.
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Re: worn cam, clatter

Post by MR2 Zig » Mon Dec 13, 2010 7:53 pm

You can turn the dist drive by turning the dist/ oil pump pulley ... its the smaller pulley on the right head. You'll have to have the cam belt off. set the crank to TDC first...like you would to change the timing belt. Chaeck the distributor position...it should point at the mark on the rim of the dist body. That way its easy to go back to where you started.


So far as I know the cam followers are normally flat.
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Re: worn cam, clatter

Post by gtv-racer » Tue Dec 21, 2010 4:04 am

Hello,

I'm also replacing my cams for the qv model ones (alfa 75 3.0v6). Does anyone know the height of the lobe of the qv ones to make sure the second hand ones are fine. Tanks!
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Re: worn cam, clatter

Post by ghnl » Thu Dec 30, 2010 3:07 pm

(GTV-racer - I don't know the specs you seek. Are these numbers not available from camshaft vendors? Typically they'll at least list maximum lift. Measure the lobe height and subtract the base circle diameter to get the intake lift measurement. The exhaust is slightly different as you have take the rocker arm ratio into account. I think that is 1:1.4 so multiply the measured lift by 1.4 to get the effective valve lift. I think.)

To update my prior questions, I bought a set of good used GTV6 heads with their good cams and followers. I cannibalized those heads for the camshafts & followers. They all looked excellent.

The old camshaft in the right side head looked very good but I swapped it, too to have a 'matched' set. Obviously I carefully swapped the followers so they stayed with the 'new' camshafts.

As for my question about cranking the engine with the camshaft removed - I did it. I had the left side cam out but the pulley & timing belt remained in place. The pulley would move outwards (towards the radiator) about 1/4" but the timing belt held it in place OK. I would not suggest doing this with both cams removed because then both pulleys might move and move too far.

So, with the spark plugs out and the left cam removed I was able to observe a good flow of oil out of each cam journal's oil feed hole at cranking speed. This reassured me that the camshaft was getting oil.

I sucked out the old oil from the area below the camshaft. It was gross - thick, black, etc. I suspect that even with reasonable care the oil under the cams is not often replaced. The pools of oil in the more easily accessable area of the head are easy to remove when the cam covers are off but the oil under the cams would need a small hose & syringe to remove. If y'all haven't done that I would suggest adding that to your occasional maintenance routine.

I then re-installed the old cams (while waiting for the 'new' ones to arrive) and cranked the engine. I observed oil flowing out of the top of the cam journals onto the camshafts (the cam journal upper halfs have a groove in them to feed oil out to the camshafts). I did notice that on the left side the rotation of the camshaft tended to splash some oil away from the pool under the cam. Since this was at cranking speed it is likely to be even more dramatic with the engine running. On the right side the cam's rotation tended to keep oil in the pool under the cam. Also, the area machined flat for the head bolts made the dam around the left side camshaft a little shallower - thus explaining why there was less oil in the pool under the left side cam.

So, in conclusion, I am hoping the cam failure can be explained by 1) use of the 'wrong' oil (too low a level of the additives needed in flat tappet engines) and B) ancient, worn out oil in the pool under/around the camshaft - much worse in the left side - leading to its early demise.
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Re: worn cam, clatter

Post by gtv-racer » Fri Dec 31, 2010 5:16 am

i had the same thick oil under the camshafts!

I also found out lift in mm on the internet:

164 s cam:
Lift for intake lobe is 10.1.
lift exhaust lobe is 8.9

gtv6 and milano:
Lift for intake lobe is 9.1
lift exhaust lobe is 8.9
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Re: worn cam, clatter

Post by xrad » Fri Dec 31, 2010 8:27 am

interesting..so you only really need to buy the intake cam..
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Re: worn cam, clatter

Post by gtv-racer » Fri Dec 31, 2010 9:49 am

one cam for exhaust and intake with the 12v engine :wink:
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Re: worn cam, clatter

Post by ghnl » Fri Dec 31, 2010 1:02 pm

Right, V6 12 valve engine has one cam/head. It has both intake & exhaust lobes. The intakes act directly via shim under bucket. The exhausts have a short push rod to a rocker arm with screw adjuster.

Also, duration (open -> close time) may be different.
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Re: worn cam, clatter

Post by xrad » Sat Jan 01, 2011 8:16 am

just see'in who is awake this year... :D
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Re: worn cam, clatter

Post by ghnl » Sun Jan 02, 2011 6:42 pm

Thought I'd add this bit of info.

Using some advice from Alfisto Steve on the AlfaBB, I made a camshaft pulley removal tool from a plumbing pipe flange. I used a flange for 1/2" pipe. By happenstance the center bolt from my pittman arm remover fit the threads in the pipe flange. I drilled two new holes and enlarged an existing hole in the pipe flange so it'd fit the camshaft pulley.

I attached the pipe flange/pulley remover tool using three 7mm X 45mm bolts with large washers. Then I tightend the center bolt until the pulley came off with a satisfying 'pop'.
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Eric Russell
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Re: worn cam, clatter

Post by xrad » Mon Jan 03, 2011 10:52 am

yeah..the usually shin banging 'POP' as the pulley flys off and hits you..

sometimes I think these are torqued on to 200ftlbs
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Re: worn cam, clatter

Post by MR2 Zig » Mon Jan 03, 2011 11:09 am

The reason it sticks so well is that its on a tapered seat....both the cam nose and wheel have tapered surfaces where they meet. As a result they lock up VERY well without a whole bunch of torque on that nut.
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Re: worn cam, clatter

Post by ghnl » Mon Jan 03, 2011 7:49 pm

Here's a question - does anyone have a photo of the underside of the different 12V V6 cam covers? This engine has the finned/block letter covers. But I believe that originally it would have had the smooth/script covers. My searches indicate the covers are considered interchangeable. But I'm just wondering if the baffles on the inside are the same...?

Today I checked the valve clearances. All were good. To gather more info about the oiling of the camshaft, I decided to start the engine with the left cam cover off.

Plenty of oil is being delivered to the cam shaft. But unless the baffle in the underside of the cam cover is effective at directing the splash back to the area around the camshaft, much of the oil is thrown away from the pool under the camshaft due to the rotation of the cam shaft. This tends to cause the left side cam run in a shallower pool of oil.
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