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MI-Bug
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PostPosted: Fri Jan 05, 2018 7:54 pm    Post subject: Was: Camshaft bearing failure - Now: Shimming the case Reply with quote

After roughly 3500 miles on my fresh 1600 SP, the engine started to make a noise. Not like a rod knock, more like a rattle. The noise would subside under acceleration but return once load was off. Long story short, I pulled the motor and tore it down. What I found was one half of the thrust surface of the cam bearing was completely gone. Shocked

My theory is that I failed to check and polish the thrust surfaces of this new cam before installing. The cam was a brand new CB 2280. Pictures below.

Am I on the right track with my theory? Any advice on how to best go about polishing up the cam thrust surfaces?

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Stock cam on the right. Note how much smoother the thrust surface appears compared to cam on left.
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Last edited by MI-Bug on Fri Mar 02, 2018 7:44 pm; edited 1 time in total
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raygreenwood
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PostPosted: Fri Jan 05, 2018 8:27 pm    Post subject: Re: Camshaft bearing failure Reply with quote

Yep....the things the books never tell you. Sorry for your loss.

You need to check, deburr and polish the thrust surface on cams. And.... use double thrust can bearings always.
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modok
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PostPosted: Fri Jan 05, 2018 8:49 pm    Post subject: Re: Camshaft bearing failure Reply with quote

I have tried to mention this whenever the subject comes up.
Many of these cams the thrust surface is far too rough and needs to be polished, the bearing faces on most brands are faced with only soft material and not able to handle a rough surface.

That said, it does not often eat clear through the steel shell.
You might suspect excessive force coming from the oil pump.

I've tried polishing it a few ways and not sure if there is a better way.
Just abrasive paper backed up with a block, spinning it in the lathe. Maybe die grinder with a cratex wheel, the wheel might wear to a nice shape to fit in there.

nice thing tho is once smoothed out, rarely do you need to do anything to the bearings. Lot of complaints the thrust play too tight, not for me, with mahle bearings. Stay away from the silverline cam bearings. Might be ok material but the thrust bearing won't sit right, three times now I have had enough struggling with it.


Last edited by modok on Fri Jan 05, 2018 8:55 pm; edited 1 time in total
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PostPosted: Fri Jan 05, 2018 8:51 pm    Post subject: Re: Camshaft bearing failure Reply with quote

modok wrote:
You might suspect excessive force coming from the oil pump.

The gear tang might be too deep into the cam.

Checking clearance is part of the "build" process.
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PostPosted: Fri Jan 05, 2018 9:00 pm    Post subject: Re: Camshaft bearing failure Reply with quote

I've run lots of different cams and including my current CB 2290 and never had to polish the thrust surface. Chances are the thrust was too tight. Most new cam bearings are complete shite and are too thick and badly formed. Make sure the thrust bearing fits the case and the thrust shoulders are square to the bearing surface. Put the cam in (if it fits) and with a light hammer and brass drift knock it back and forth a couple times to set the thrust surface, this will also square it up if it's off a bit. Make sure you have at least .0015 to .002 clearance. If not sand it on a piece of glass on some fine wet/dry paper. I use 1000 grit. Go slow and keep it even.

brad
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PostPosted: Fri Jan 05, 2018 10:56 pm    Post subject: Re: Camshaft bearing failure Reply with quote

if the oil pump drive gear is not floating as it's supposed to, it can wipe out the cam thrust bearing. This is one reason setting the drive tang depth is so important (and not in the books).
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PostPosted: Fri Jan 05, 2018 11:01 pm    Post subject: Re: Camshaft bearing failure Reply with quote

When they say 'drop-in' does not mean just drop them in. YOU have to check for proper clearances.

Cam gear to crank gear backlash, thrust backlash, rod side clearances, all endplays..so on...all part of the build.

Sorry for the loss but at least you now have first hand knowledge of engine failure. I have no doubt the next engine build will be way better.
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MI-Bug
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PostPosted: Sat Jan 06, 2018 7:15 am    Post subject: Re: Camshaft bearing failure Reply with quote

Thank you gentlemen for all your wisdom! I, no doubt, will be double checking all clearances and will be polishing the thrust surfaces of the cam as I build this engine again. I'm approaching this failure as a learning exercise and looking forward to having a sweet running motor.
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PostPosted: Sat Jan 06, 2018 9:27 am    Post subject: Re: Camshaft bearing failure Reply with quote

MI-Bug wrote:
Thank you gentlemen for all your wisdom! I, no doubt, will be double checking all clearances and will be polishing the thrust surfaces of the cam as I build this engine again. I'm approaching this failure as a learning exercise and looking forward to having a sweet running motor.


And.....use the double thrust cam bearings. While its 100% correct that it could most probably be excessive pressure on the thrust flange from oil pump clearance......having a flange that is only 50% the diameter of the cam journal means that whatever pressure is on it....is concentrated in an area that is half the size/area of what it COULD be.

http://vwparts.aircooled.net/Double-Thrust-Cam-Bearings-Type-1-Based-Engines-p/111-198-541hdbr.htm

For $24.95.....thats just stupid cheap insurance. Ray
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PostPosted: Sat Jan 06, 2018 11:30 am    Post subject: Re: Camshaft bearing failure Reply with quote

that cam may not be usable....
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PostPosted: Sat Jan 06, 2018 12:11 pm    Post subject: Re: Camshaft bearing failure Reply with quote

not cam related but also check dist. drive gear end play,with crank and dist. installed, gear can be shimmed tighter then stock setting, its the little things that add up to problems some times.
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PostPosted: Sat Jan 06, 2018 2:43 pm    Post subject: Re: Camshaft bearing failure Reply with quote

I spent some quality time with 320/400/600 grit wet/dry sand paper this afternoon polishing the thrust surfaces (and cam lobes too). I'm liking how it's coming along. Appreciate all the comments!

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PostPosted: Sat Jan 06, 2018 3:22 pm    Post subject: Re: Camshaft bearing failure Reply with quote

oops
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Last edited by slalombuggy on Mon Jan 08, 2018 8:56 am; edited 1 time in total
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PostPosted: Sat Jan 06, 2018 5:39 pm    Post subject: Re: Camshaft bearing failure Reply with quote

That'll work.
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PostPosted: Sat Jan 06, 2018 11:27 pm    Post subject: Re: Camshaft bearing failure Reply with quote

parkerizing all gone...( that black stuff on the lobes helps hold/absorb oil where it needs to be). next question....did the flange wear away? or did it snap off??Ive seen some snap off(also seen crank thrust broken off) be sure to check thrust clearance..I would lather that sucker up with camshield molly lube for sure..lifters too...and be sure to use duel thrusters too.
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PostPosted: Sat Jan 06, 2018 11:42 pm    Post subject: Re: Camshaft bearing failure Reply with quote

It's just a moly paste, I asked Webcam a while ago about it coming off. They said not to worry too much but to make sure they all got some assy lube on.
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PostPosted: Mon Jan 08, 2018 2:48 am    Post subject: Re: Camshaft bearing failure Reply with quote

I polished my lobes as well, yes maybe the black oxide, parkerizing, hold some more oil, but from what i learned in tribology class is that less surface roughness is always favorable when you have steel surfaces against one another, and from the tests we did during labs, that also bears out in longeviety/wear of the parts as well. The hardening should not be affected by polishing as the depth of the hardening should be significantly deeper into the material.

I had to polish the thrusts as well on my engle FK-87, i could not get either Mahle or Silverline to even fit before i did so, dont know if the cam manufactureres are at fault or the bearing manufacturers. But since it seems that main bearings are getting worse and worse, i tend to lean towards the bearing manufacturers.....
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modok
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PostPosted: Mon Jan 08, 2018 2:50 am    Post subject: Re: Camshaft bearing failure Reply with quote

Both.
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PostPosted: Mon Jan 08, 2018 4:18 am    Post subject: Re: Camshaft bearing failure Reply with quote

yeah, that is probably true.... unfortunately
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PostPosted: Mon Jan 08, 2018 9:00 am    Post subject: Re: Camshaft bearing failure Reply with quote

Tobias Bylund wrote:
I polished my lobes as well, yes maybe the black oxide, parkerizing, hold some more oil, but from what i learned in tribology class is that less surface roughness is always favorable when you have steel surfaces against one another, and from the tests we did during labs, that also bears out in longeviety/wear of the parts as well. The hardening should not be affected by polishing as the depth of the hardening should be significantly deeper into the material.

I had to polish the thrusts as well on my engle FK-87, i could not get either Mahle or Silverline to even fit before i did so, dont know if the cam manufactureres are at fault or the bearing manufacturers. But since it seems that main bearings are getting worse and worse, i tend to lean towards the bearing manufacturers.....



Your tirbology class failed you....gwasshoppa..... Wink ..sort of.....I am just happy you have the class and are paying attention! We need more of that!

What you have not taken into account.....is that the black phosphate coating is a conversion coating....not just a hot dip coating. Its hardness.....is many orders of magnitude lower than either the lifter or the cam lobe.

Its a sacrificial coating that is not designed to be long lasting. Its designed to produce a greater Ra (generally put....becaue that also affects Rz, Rv, Rp, Rt etc.).....that holds oil during break in...on a metal surface whose surface profile is far too smooth to hold any significant oil itself.

This method is even used ....on the cylinder walls....in the form of the cross hatch grooves....for two reasons.....one precisely as noted above to hold oil and two....to produce a surface of uniform tooth to properly wear the rings into the proper shape. In that case.....you have one fairly hard surface and one greatly softer surface....in comparison.

The lifter and lobe relationship is a little different. Both parts are relatively hard and have a very different "type" and range of friction applied between each other.

But....its most probably not going to be a problem as Web Cam noted. The black oxide coating is generally put there as extra insurance that the right anti-scuff/anti-galling EP additives are there at the surface in high quantities during the most crucial break in period.

By the way.....it is NOT true....with all bearing and load surfaces that smoother is always better. You need to have the correct LEVEL of smoothness.

For instance.....it would be very easy to polish the crank journals to a total mirror smoothness far beyoned what is done after grinding the crank. And if you do that.....you can actually make the surface smooth enough that there is no surface area whatsoever to hold any oil. The micro valleys in the surface ....for lack or a more descriptive term...will be too shallow.

It matters what kind of metal.....and it also matters what kind of lubrication system. On crank journals.....very smooth is good.....like an Ra of around 15 micro inches or a little less....but these do well with smoother....because they are FORCE FED....pressurised with oil. Smoother is better.

However the cam lobes are splash fed. They need SOME tooth but will develop their own as they wear in.

By the way for reference....10 micro inches Ra....is right about what my surface profile gauge reads on standard plate glass. However.....in a piece of "half wave" optical flat glass....the gauge does not read anything....0.....but thats just a tolerance issue with my gauge. We are talking Angstroms on that glass. Ray
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