Re: Camshaft troubles 71 Chevy truck

Posted by Mark - IN. on December 28, 2008 at 21:03:48 from (205.188.117.74):

In Reply to: Camshaft troubles 71 Chevy truck posted by Bob Kerr on December 27, 2008 at 23:28:11:

You're going to want to pull that guy and open her up to clean things out. Those metal bits end up in the screen of your oil pump pickup tube sump and end up plugging it up, next will be spun bearings. I hate to say it, but if its me that engine's coming apart and the plugs are coming out on the end of the block and its getting rodded with a wire brush (gun cleaning kit), then its getting flushed, hot tanked and rebuilt. I'm sorry, times are tough, cash isn't readily available to many including me, but the cost of having a crank welded up, ground down, and rods resized or replaced after spinning a bearing, and the other damage caused is just going to cost even more $$$.

You didn't say small or big block though. I did a friend a favor one time and really screwed him royal. Had a '70 402 and needed a new hydraulic cam quick, and I just happened to have a mildly rougher street Crane Fireball still setting in the box. It was for a '67 or '68 427, which isn't and is a problem. There was a change in lubrication on the rear journal in '69 which meant that you couldn't use cams from '68 and prior without modifications. '68 and earlier cams had a big groove (very noticable) cut around the whole diameter of the last journal for oiling, but the bearing itself had a very small hole, like 3/16" that worked like a dam to regulate the oil flow. That design was changed in '69 whereas the rear cam journal didn't have that groove, and to compensate, Chevy put a huge hole in the bearing itself for oiling. If you use a '68 or earlier cam in a '69 or later big block, you have to solder that hole shut in the bearing, and then redrill at about 3/16" of an inch. Failure to do so...bad news. Very bad news. Combine that big oiling hole in the bearing with that big groove around that last journal, and you will lose almost all oil pressure to the rest of the engine. I knew that, but didn't think about that when I gave my buddy that cam...for free, and when he put it in that freshly rebuilt 402 and fired it up, no oil pressure and it became scrap in seconds. He had no idea what happened, but after he told me about it, what happened took about 3 seconds to register...I screwed up doing a friend a quick off the cuff favor late one night when he came over and needed one.

Mark

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