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#1
IP: 216.9.107.21
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Camshaft During Engine Overhaul. Refurbish? Replace? Repent? Retreat?
Hi all,
Some of the many helpful frequent contributors may recognize I have an ongoing absurdly longwinded rebuild thread (just like the rebuild itself) but I wanted to pose this question separately since it's fairly specific. About 2.6 seconds after I got off the phone with Ken last week ordering every single moving part the Atomic 4 possesses, I realized we hadn't discussed the camshaft. In other contributors' rebuild threads, the only consideration I had seen regarding the camshaft was the relatively "soft" brass(?) camshaft bearings that could be damaged by "hot tanking" the block or careless reinstallation of the cam. In absence of any clear direction I took my camshaft up to the machine shop who's doing the block work. The shop owner took a look at the cam and cautiously advised I send the cam off to get "cleaned up" and "hardened" and provided the contact info to a company in Oklahoma. (I'm rebuilding the engine at home in Denver even though the boat is in San Francisco) He expressed concern over the surface rust on the cam lobes and hypothesized it would only cost around $65-ish for the necessary work. Understandably, I echo his sentiment that "you've spent this much money/time/effort on this project you might as well leave no stone unturned." My question is twofold. First, based upon these pictures would y'all be comfortable reinstalling this camshaft in a fresh rebuild? Second, does anyone know what "rebuilding" a camshaft involves? What does a 'hardening' process involve? Assumably if any material was machined off the camshaft, like a crankshaft, would likely need to be replaced with weld and polishing? What about the lobes? How would they assure the profile remained unchanged? Before someone suggests it, I'll point out that yes, I know our great host sells used camshafts for $125 and that's obviously an option. Frankly my only hesitation is that even the picture in the MMI catalogue appears to have some surface wear on the lobes as well. Moreover I'm just interested in whatever wisdom the braintrust has to offer on camshafts, hardening, tappets, best practices, etc.
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Jonathan 1979 Catalina 30 #1497 An old Airline Pilot proverb: "If we don't help each other nobody else will." |
#2
IP: 216.9.107.21
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And if anyone is interested enough, here is the contact that was recommended to me by my machine shop:
http://willhoitescams.tripod.com (Obviously not an endorsement since I haven't even contacted them yet but in case someone was curious as to who was recommended.)
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Jonathan 1979 Catalina 30 #1497 An old Airline Pilot proverb: "If we don't help each other nobody else will." |
#3
IP: 12.230.196.198
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HI McQ
I always enjoy reading your posts but now i am confused. Please fill us in on your story. I thought you rebuilt this engine a long time ago and are just now telling your story in a very interesting narrative. What is the real scoop? Are you currently rebuilding your engine or was it done a while ago. If so where are you at currently and when did the historical narrative stop?
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Jim Zeller 1982 Catalina 30 Kelleys Island, Ohio |
#4
IP: 40.132.224.194
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Hi Jim,
Yeah sorry for the confusion. I know it's generally frowned upon to have multiple threads going for the same engine rebuild but I was trying to avoid confusion since I'm not up to date with my 'rebuild thread' posts. I know I've been a little behind but I'll catch up I promise. To clarify the timeline, I purchased the boat with the non-running A-4 in 2013, tinkered with every engine system from 2013-2015 to diagnose the non-running condition (where my 'rebuild thread' narrative is currently stalled), ultimately got the engine running, then made a couple of significant screw-ups that likely caused enough damage to require the full rebuild, and now am currently in the middle of a slow-but-steady full teardown/rebuild (Oct 2018.) I didn't want to ruin the timeline and quickly skip through the story of how I toasted my engine just to catch up to present-day. It's informative and hopefully entertaining enough to be worth the wait. -Jonathan P.S. I hope the A-4ians will forgive my infrequency of posts for the time being. However, if anyone wants a taste of what it's like being in the throws of an ongoing multi-year whole-house renovation while dealing with a crying, screaming, sleepless, teething 13 month old who uses your nose as a chew toy, living in a semi-finished construction zone with 1 functional toilet, sleeping on an air mattress on the floor, covering 2 mortgages and full-time daycare, er, I mean 3 mortgages, supporting a stressed-out, sleep-deprived wife, and then commuting 997 miles to work at a job with a company that's in the middle of a merger, while trying to squeeze in 1 hour/month to work on your old busted sailboat motor, I can post a video on YouTube so you can get a better feel for the audio. Believe me the sound is worse than any rod knock you've ever heard!
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Jonathan 1979 Catalina 30 #1497 An old Airline Pilot proverb: "If we don't help each other nobody else will." |
#5
IP: 107.77.97.120
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It's kinda hard to tell, but I think you have a little surface rust on the base circle in the last snapshot. Probably from off-season storage.
Not a biggie. Take it to a machine shop and have them lightly polish it. Sometimes they call it "micro polishing". It looks like the bearings could use that love too. It's the same grit belt they use to do the final polish on a crank after it's been ground or just handled poorly by mechanic. A polishing belt is best after it's broken in. New ones take too much. Re: cam grinding, When an old cam(a core) is ground, the base circle is ground too. The lift remains the same. Or , if you are modifying it like a hot rod, some changes are made in the new profile. I think they may flame harden after this(?) A regrind probably costs more than a good used cam from MMI. I have even installed cams without polishing them in a few old timers—it's a judgement call. Rock on, Russ
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Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1 "Since when is napping doing nothing?" Last edited by lat 64; 10-30-2018 at 12:20 PM. |
#6
IP: 137.200.32.54
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So how about a hot cam?
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