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Hi, I`m looking for concepts to restore a camshaft with to much wear. From my unexperienced point of view I see three options: 1) Metal-spray and machine the camshaft journals. The bearing ID`s to be machined to match with 0.001" clearance for oil. 2) Machine the bearing ID`s and babbitt them. Machine the camshaft journals to undersize diameter.
The babbitted bearing ID`s to be machined to match with 0.001" clearance for oil. 3) Find modern bearing shells which could be machined into the bearing ID`s and then machine the camshaft journals to match with 0.001" clearance for oil. The job is to search for the right modern bearing which fit most. I`m interesting to learn about your experiences, recommendation and which shop are doing this work

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No wear on the cam lobes themselves, just the bearing journals?

2470Packard,

I had the same problem with excess cam bearing journal clearance on a '32. I ended up having the cam journals metal sprayed then ground back. The cam bearings in the block were machined to give the correct oil clearance.

The shop that did the work was:

deltacam.com/services.php?p=2

They also checked the cam for straightness and reground the cam lobes. Have the shop you select check for run-out of the base circle of each cam lobe to the cam bearing journals.

If the place you take your camshaft to doesn't know how to check this I'd advise finding some place else.

The long camshaft in the straight 8's can have individual cam lobes bent off center. The cam journals may be inline but you can have one or more cam lobes off center.

I speak from experience on this, I had to pull an engine apart to remove the cam after my "expert" machine shop told me the camshaft was checked for straightness and was OK.

All they did was check the journals, not each cam lobe. After three months of trying to diagnose a bad running engine I put a drop indicator on each of the cam lobes and rotated the cam in the engine. What I saw was .010 run-out of the base circle of the cam. This told me a few of the lobes were bent off center.

Regards,

Dave

Owen,
my main task was about the camshaft journals, but of course it is also interesting to know about how to rebuild the cam lobes. The link Dave sent is very useful.

The reason I asked the question is that in my experience with the 385 & 320 engines, the lobes will show wear long before the bearing journals.

I am not familliar with the clearances for cam brgs on the 320/384 motors. We manufacture about 30 different cam bearing sets for US cars '34-'70 and most have clearances in the .003-.004 range, nothing has .001.

I am wondering where you got the spec of .001?? It would seem to me that a 320/384 with a cmashaft longer than most other engines would have a runout greater tatn most other engines necessitating generous clearance.

2470Packard,

I've attached some info on Packard engine bearing clearances and recommended clearances for engines of the same period.

Also a publication from Clevite gives some insight into the topic.

As a general rule .001 inch clearance per 1 inch shaft diameter is acceptable for sleeve type bearings.

Regards,

Dave

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I don't recall the diam of the early camshaft journals which are smaller than the later cams, but it's about 2.500 which would require a clearance of about .003.

2470Packard,

One thing to keep in mind when machining or grinding your cam journals, the cam bearings need to be line bored or honed to size, in the block, to assure they are all on the same axis.

If the cam bearings were machined with .001 clearance to the cam journals outside of the crankcase and then assembled the cam will be tight and you will not have the proper oil film clearance in the cam bearings.

Also the block needs to be torqued to the crankcase when this is done to assure the cam bearings will still be in line when the block is assembled to the crankcase.

One example of line boring equipment for cam bearings:

sunnen.com/ProductDetails.aspx?ProductID=37&NavID=678

In addition to size, the machined bearing surfaces need to have the correct finish, taper, and out of round.

Links with some useful info:

engineparts.com/publications/CL77-3-402.pdf

mahleclevite.com/it_cambrgs.asp

mahleclevite.com/techbulletins/CL77-1-205R.pdf

stealth316.com/misc/clevite-eng-bearing-fund-p2.pdf

Regards,

Dave

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Dave, those articles were well worth taking the time to read. Thanks for providing.