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Old 06-27-2015, 10:45 AM   #1
148am OP
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Post-machine shop cam journals

Picked up my DRZ's head from the machine shop yesterday and in my rush to beat their closing time, I, well, rushed out of there. It got a valve job.

What used to be smooth/honed cam journals are no longer smooth after they cleaned. Will the cams find their own seats during break-in, or did I just get screwed?

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Old 06-27-2015, 11:27 AM   #2
stainlesscycle
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ooh. nasty. bead blasted bearing surface = bad news.
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Old 06-27-2015, 11:34 AM   #3
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Is that what it is, I can't tell from the photo? Why would a machine shop do that, they must know that's a plain bearing surface.
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Old 06-27-2015, 11:39 AM   #4
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Check the clearance, but this should be OK ( not a good situation though!! I wonder about the quality of the valve job ?? ). If glass bead was used, you will be good. The cam is very hard and will wear in the roughed up surface quickly. Bear in mind the bead blast did removed some material form the journals. If you can, lap the rocker cover to tighten up the cam bearing clearance to minimum before re-assembly.
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Old 06-27-2015, 02:19 PM   #5
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I'm not sure from that pic its actually been blasted, it also looks like it could be fresh out of a US cleaner.

Also since plain bearings rely on oil pressure to create a barrier of oil to function some embedded glass shouldn't do anything since the only time the cam touches the journal is when its not running and for a few revolutions at initial start up.

Further even if it was media blasted, it could have been plastic, crushed walnut or soda. All relatively safe inside a engine
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Old 06-27-2015, 03:27 PM   #6
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Quote:
Originally Posted by Skowinski View Post
Is that what it is, I can't tell from the photo? Why would a machine shop do that, they must know that's a plain bearing surface.

A lot of guys have no idea that there are engines that do not use insert bearings. He may have thought no problem with blasting it.
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Old 06-27-2015, 04:18 PM   #7
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Let's assume the head is clean. Place a couple drops of oil on the journal and then take a strip of 600 wet/dry sandpaper and lay it in the journal. With the cam and it's end bearings put it in place and work the sand paper back 'n forth a couple of times while pressing the cam down but not so hard as to tear the paper. You may need a second set of hands to do this. What you want to achieve is to knock down the high spots of the journal. When you assemble the head use a good Moly assembly lube.
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Old 06-27-2015, 07:05 PM   #8
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What you really need to do is go back to the machine shop on Monday and commence negotiations with the owner. They absolutely need to show you that the bearing surfaces can be put back in spec, or make it right if they can't be
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Old 06-27-2015, 07:10 PM   #9
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I've never known a machine shop to bead/soda/sand blast engine parts. I think most use a dip tank or an ultrasonic cleaner. I've yet to visit an engine machine shop that possessed a blaster.

Cleanliness is of utmost importance in engine parts, be they auto or cycle, and blast media would be hard to contain in a shop environment. Be careful before you rip the shop guy a new asshole-ask nicely first.
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Old 06-27-2015, 07:36 PM   #10
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I'm not holding the part but kinda looks like a dulling reaction from a cleaner on the aluminum instead of a media finish.
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Old 06-27-2015, 07:46 PM   #11
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I don't see how that's going to work. Yes, the cam rides on an oil film, but creation of that film depends on there being a specified clearance between the cam and saddles so the oil doesn't escape too quickly. It looks like your cams are direct-acting, which means that the load is on the upper half of the saddles, but you still need to worry about generating enough oil pressure to support the cams.
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Old 06-27-2015, 07:52 PM   #12
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I'll bet it wasn't blasted. I think I can still see a scuff from disassembly. Check the clearances with plastigauge. If the clearances are ok and the shop guy says he didn't blast it you are good to go.
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Old 06-27-2015, 09:37 PM   #13
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I agree, clean everything super good & check clearances. if it's in, good to go. if not.... there are things you can do.

blast media has a tendency to stick in tight places and particularly in oil passages. looks like the spring seats are still in the head.... if it was blasted there will be stuff to clean. pull them for cleaning & be sure they are back in when you install the seals
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Old 06-27-2015, 10:37 PM   #14
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If, as you say, it got a valve job then why don't i see the valves installed. What exactly did they do to the head?
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Old 06-27-2015, 11:47 PM   #15
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If the surface was bead blasted the problem is geting all the shit out of the bearing surface and oil ways. The beads break up on contact and the abrasive dust not only gets everywhere, it embeds itself in the base metal. *That* is going to be your major difficulty.
Cleanliness is beyond godliness inside an engine. A trip through a washer in not likely to do it. Clean clean clean. Once you think its clean, do it again. Spray it with wd40, then wipe it over with clean white kitchen paper, it should come off completely unmarked, absolutely no colour. Then work out how to do that in the oilways

Once at work, some aluminium which should have been vapour blasted was put in the wheelabrator - quite a harsh and drastic process in our normal application of removing mill scale from ferrous parts.
We trundled off to inspection with a few samples and despite some very obvious visual changes, the surface texture of the aluminium was still within spec.
Dimensionally, some very sophisticated measuring equipment was not able to detect any changes to outside of range.
So although I'd check, it would not be a major concern other than trying to find a stick to beat your machine shop with.
Hope it works out for you.
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