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Re: worn cam, clatter

Posted: Tue Jan 04, 2011 10:18 am
by xrad
I have finned script covers with grid ribs, and no lubrication issues(that I know of). Although oil is splashing around, Is there enough oil pressure?

Re: worn cam, clatter

Posted: Tue Jan 04, 2011 5:00 pm
by ghnl
Oil pressure via dash gauge (new sender) is good. With a warm engine about 20 psi at idle, 65-70 psi running (~ 2,000 rpm & above).

Re: worn cam, clatter

Posted: Wed Jan 05, 2011 8:41 am
by xrad
really looks like lack of oil to that area..but why. were the camshaft bearings at caps OK?

Re: worn cam, clatter

Posted: Wed Jan 05, 2011 8:55 am
by kens
I speculate that the damage could have been the result of having some coolant in the oil at some earlier point. However, I don't have experience with what the results of a bad gasket letting coolant into the oil system. Can anyone confirm what oil-coolant mix damage looks like? And/or why would any kind of lubrication problem be so localized?

Re: worn cam, clatter

Posted: Wed Jan 05, 2011 2:17 pm
by ghnl
xrad wrote:really looks like lack of oil to that area..but why. were the camshaft bearings at caps OK?
Cam bearings all looked fine.

What leads you to believe that there is a lack of oil? When I watched the area with the engine running (at idle with cam cover off) there was a steady flow of oil bathing the camshaft. The only 'issue' I noticed is that the rotation of the camshaft tends to throw oil out of the pool it rides in.
kens wrote:I speculate that the damage could have been the result of having some coolant in the oil at some earlier point.
Certainly possible - I don't know every detail of the engine's history. However the right side cam shaft looked/measured fine.

I do know that the PO had used Mobil 1 (15w-50 IIRC). On the motorcycle forums I subscribe to Mobil 1 has lost favor due to its lowered zinc levels. Motorcycle engines needs such additives both for the camshafts and the gears (most motorcycle transmissions share their oil with the engine). But again, if I blame the oil, why did it not affect all the camshaft lobes? Or perhaps I happened to catch it as the wear was starting?
Can anyone confirm what oil-coolant mix damage looks like? And/or why would any kind of lubrication problem be so localized?
Coolant (water) mixed into oil tends to look like "chocolate milkshake".

Coolant is obviously not a good lubricant. It can wipe out bearings very quickly but I suspect it'd ruin crankshaft bearings first and also ruin things more equally. The damage I found was in some (but not all) cam lobes & followers.

Re: worn cam, clatter

Posted: Thu Jan 06, 2011 12:58 pm
by gtv-racer
A question about the cam followers. Can you lahte them down if the surface is worn . I mean the surface where the camlobe meats the camfollower.

Maybe it gets to thin.. Anyone?

Re: worn cam, clatter

Posted: Thu Jan 06, 2011 10:01 pm
by Typhoon90
I really don't think this is an oil pump/oil quality issue. Cams just wear through the surface hardening eventually, it's how it is. The cam and lifter are a metal on metal sliding surface, separated by a oil film. The things that can cause a cam lobe to wear through are numerous:
*Poor manufacturing, resulting in insufficient hardening depth (very common).
*Poor manufacturing, cam blanks cast with impurities. Shows up fine when cam is surface finished, but small voids and imperfections can be quickly exposed as cam lobes wear, causing fast wear.
*Lifter stops rotating ( lifters are ground with a slight convex face and ride slightly offset from the cam lobe centreline. This is meant to make lifter rotate and promote even all over wear of the lifter face and cam lobe. The cam lobe is often also ground with a slight taper across the lobe face, to match this convex and also to provide a thrust moment that ensures consistent thrust bearing contact of the camshaft in it's thrust bearing, so the cam doesn't knock back and forth).
* Sticking lifter. See my comment previously about rust pitting on lifter.
*Over revved engine. Valve float is incredibly hard on cam lobes, it pounds them very heavily and will wear through surface hardening very quickly.
*Too tight valve lash. Creates a lot of friction, which means heat, which causes "pick up" of metal. Too tight valve lash could also cause bottoming out of the rocker/valve assembly, which will also hammer out the cam lobe.
So, as you can see, there are many, many factors involved, on an engine that doesn't show any obvious oil pressure or oil related issues, I'd be looking at any of the above first.
I've had a cam in a Ford V8 wear through it's hardening due to old age and me over revving it ONCE, plus have had a couple of motorcycles whose engines had a pre disposition to wearing cam lobes horrendously. This is thought to be a surface hardening issue in this case.
I've studied this area a lot and have a lot of evidence and experience to back up my statements above.

Regards, Andrew.

Re: worn cam, clatter

Posted: Thu Jan 06, 2011 11:11 pm
by scott.venables
Typhoon90 wrote: .... *Lifter stops rotating ( lifters are ground with a slight concave face and ride slightly offset from the cam lobe centreline. This is meant to make lifter rotate and promote even all over wear of the lifter face and cam lobe. The cam lobe is often also ground with a slight taper across the lobe face, to match this concave and also to provide a thrust moment ......
Andrew I think you meant convex?

Cheers, Scott

Re: worn cam, clatter

Posted: Fri Jan 07, 2011 2:50 pm
by Typhoon90
scott.venables wrote:
Typhoon90 wrote: .... *Lifter stops rotating ( lifters are ground with a slight concave face and ride slightly offset from the cam lobe centreline. This is meant to make lifter rotate and promote even all over wear of the lifter face and cam lobe. The cam lobe is often also ground with a slight taper across the lobe face, to match this concave and also to provide a thrust moment ......
Andrew I think you meant convex?

Cheers, Scott

Thanks! Always a VEXing problem!.

Regards, Andrew.

Re: worn cam, clatter

Posted: Tue Feb 08, 2011 7:04 pm
by ghnl
How wide should the conecting rod's big end bearing shells be in relation to the rod itself?

I am still working on locating the clattery noise I don't like from the engine of our GTV6. I was hopeful replacing the worn camshaft (and the tappets) would solve the issue. It is better. The constant clatter I described as like a baseball card in bicycle spokes is gone. But there is still a noise that makes me think of a rod knock.

The knock or rap is present on acceleration and much less on decelleration. I suspect the noisy camshaft masked this noise earlier. Ignition timing is correct and it does not sound like pinging.

So, as curiosity mounted, I decided to drop the bottom half of the sump to see if I could discern any issues with the rod bearings. I can detect no looseness/movement about the circumference of the journals but I can move each rod side to side a fraction of an inch. Enough that I can make them 'click' against the sides of the crank. There is no discernable movement of the crank itself in the main journals.

The big ends of #2 & #5 are easy to access with the bottom half of the sump removed. Those bearings look fine. The crank journals look fine. But I did notice something confusing to me. The rod bearing shells are narrower than the rod's width. In other engines I've worked on the bearing shells are always as wide as the rod. I assume if the bearing shells were as wide as the rod then the rod would tend to stay centered in the journal due to the small radius at the sides of the journal.

Could this be the source of the clattery noise? Should I just turn up the radio?

Re: worn cam, clatter

Posted: Wed Feb 09, 2011 6:14 pm
by ghnl
I found a photo in the 164 section of the AlfaBB. This photo shows what the big end bearing shells looks like - very similar to what I saw in our GTV6.

Still doesn't explain the noise I am hearing...
big end bearing - 164.jpg
big end bearing - 164.jpg (33.89 KiB) Viewed 3257 times

Re: worn cam, clatter

Posted: Fri Feb 18, 2011 6:02 pm
by ghnl
So, still trying for a diagnosis, I dropped the lower half of the sump (again) and removed the oil pump to get a look at the #1 & #4 rod bearings.

It appears I found a problem. I am hoping it is the problem.

(that is a reflection going across the bearing shell)

Re: worn cam, clatter

Posted: Fri Feb 18, 2011 6:05 pm
by fedezyl
They do look worn, is rod offset ok?