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post #16 of 20 (permalink) Old 08-05-2016, 05:08 PM
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Re: 77 T-bird camshaft replacement (wiped lobe)

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post #17 of 20 (permalink) Old 08-18-2016, 12:10 PM Thread Starter
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Re: 77 T-bird camshaft replacement (wiped lobe)

All of my camshaft journals look like this. What do you think? Are the journals lubed with pressurized oil or splash? Are my camshaft bearings salvageable? How do I know that my bearings will have proper clearance for my new shaft?

What are some orifices/passages in the oil galleys that I can access without removing the heads or block? I plan to take the sending unit out to see if there's any trace of metal. I can't believe how minimal the junk in the oil was, or maybe I can after so many oil changes.

Thanks, ready to knock this out.

I believe at this point that this cam was wiped as soon as we tried to start it. Sitting for 5-years, every drop of oil would have hit the sump. When I went to purchase the car, the owner was cranking and cranking for well over 5-minutes (on and off) and in all that time not a drop of oil would have ever hit the lobes. It's a wonder only one was wiped, and it isn't even flattened, just dished the lifter and lost a little height at the apex.
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Last edited by Mason81; 08-18-2016 at 12:29 PM.
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post #18 of 20 (permalink) Old 08-19-2016, 02:41 AM
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Re: 77 T-bird camshaft replacement (wiped lobe)

Your bearings appear to be OK. If the cam journal bearings were contaminated, you would see full-circle score lines on the cam journals. Check all of them. If there is not substantial scoring, then you should only have normal wear, which is generally minimal in these engines. The journals are pressure-lubed. You can access the lifter oil galleries by pulling the plugs at the front of the block. But if you do not have any scored journals, then there likely isn't anything left in there to remove by now.

Cam lubrication trivia: OK, ready to hear a huge myth busted? The reason for elevated rpm during cam break-in is not lubrication by splashing. It is to have enough surface speed for the lifters to hydroplane on the oil film, to prevent the fresh microscopically-rough surfaces from galling under the high contact pressure. When the damage is viewed, the typical reaction is that lubrication was not sufficient, when in-fact the oil flow from the bottom of the lifter bores is substantial. Oil pukes from those puppies. This is one reason pre-lubing is highly regarded in critical engine applications before first start or after long storage, as pressurizing the system covers the parts—including cam lobes—in oil, providing lubrication before any parts move.

While the flat-tappet lifter spins due to edge contact on the slightly angled surface of the cam lobe and convex surface of the lifter bottom, it can throw-off much of the oil onto the lobes nearby. This is one source of the "splash" lubrication you hear about. Another is oil thrown by the crankshaft, and oil mist from anything moving. With the direct flooding from the bores, and all of this splashing, even at cranking speeds, the lifters are slobbered with oil. So, with all this oil, the missing element is enough speed for the lifters to ride on the "oil wedge", and therefore the recommended raised rpm during break-in. Once the surfaces are smoothed and slightly worn-in , the rpm can be reduced without losing enough oil wedge clearance to cause galling. More than you wanted to know, eh?


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post #19 of 20 (permalink) Old 08-19-2016, 03:08 AM Thread Starter
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Re: 77 T-bird camshaft replacement (wiped lobe)

Actually, I'm glad you enlightened me. I can't believe how I overlooked the fact that the oil to the lifters would obviously slather the lobes! Duh!

I'm glad I don't see a single scrape on any of the cam journals. The only damage is #4 exhaust lobe, and it isn't flat, it's just lot its apex. About 0.12" difference. It would drive great but would just lope at idle as #4 became very intermittent.

I just stabbed it in an hour ago. There is negative end-play clearance so I'll apparently have to grind something down to get some freeplay. Suggestions so I don't cut too deep?

Last edited by Mason81; 08-19-2016 at 04:29 AM. Reason: I just realized cam endplay is measured with the sprocket on :)
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post #20 of 20 (permalink) Old 08-25-2016, 05:21 AM Thread Starter
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Re: 77 T-bird camshaft replacement (wiped lobe)

The operation is complete.
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