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G-MAN
07-02-2002 16:12:09
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Re: Re: Re: Re: Camshaft and cam followers machining issue in reply to mike, 07-02-2002 15:09:22
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Apparently you missed the main point of my post. I stated the I had talked to someone that I consider to be an expert on the subject (Robert of Robert's Carburetor Repair), and his opinion is that a lot of two-cylinder cams were improperly or inaccurately machined when they were new - leading to uneven idling, carburetor spitting, etc. He also stated that these symptoms usually aren't noticed in the stock tractors due to the style of intake systems, stock hp levels, etc. I know that he's trying to sell a service - everybody is trying to sell something. I'm a JD tech, and I try to sell customers service work everyday - because it benefits us both. I wouldn't try to sell something that wasn't necessary. I have seen countless posts about Robert's, and have yet to see someone complain or say he hoodwinked them. If the cost was something outrageous, I would think twice. And there is no doubt that there are lots of tractors running with worn or pitted camshafts in them. Your comment about Chevy engines running faster is a good one, but you don't see a lot of 50 year-old small-blocks running around either. You also don't see a lot that were pulled at full-load for 12 or 14 hours a day dragging a plow. You also need to consider what kinds of lubricants were available when these tractors were new. Not to mention the fact of oil dilution from kerosene and the less than perfect filtration provided by oil-bath air cleaners. Both of these factors contribute to engine wear. You state that a regrind isn't worth the money. I guess if I were going to spend $150 for a bore job, $400 for new pistons and rings, up to $300 or $400 for head work (valves, guides, seats, springs, planing, etc) and who knows what else on the rest of the engine (rod bearings, governor rebuild, carburetor repair, magneto, etc), I wouldn't think $100 to $150 for getting the cam reground would be too out of line. BTW - I will be doing all these things to my '48 G, and the cam and lifters will be reground as well. Seems kind of stupid to ignore one of the main influences on an engine's performance when it's laying there on the bench - especially considering how much work is involved in removing it. Not to mention the fact that the cam can be reground to increase the overall performance of the engine. I'm interested in hearing how you determine the quality of a camshaft. How many camshafts have you put in a set of V-blocks and checked the lift on? You surely know that a camshaft lobe is ground at a slight taper when new and the lifter with a slight convex surface to promote rotation and reduce overall wear to both surfaces. I don't care how good the lobe looks, if these features are worn off, the camshaft will not perform properly. A crank journal can be nice and shiny too, but are you still going to run it if it is out of round or tapered? Your call. You can do whatever you want with your tractor, and the guy did ask for opinions, but don't sit there and tell him that JD two-cylinder cams don't wear out, because the fact is that they can and do. If they didn't, there wouldn't be specs for measuring them. I've yet to see the internal engine part that wasn't prone to some type of wear, regardless of the engine or application.
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