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Posted by D Sherman [24.32.202.83] on Tuesday, May 18, 2010 at 18:23:00 :
In Reply to: Re: engine problem found. thanks to all.. posted by D Sherman [24.32.202.83] on Monday, May 17, 2010 at 19:36:23 :
It's made by Sunnen-Sioux, looks to be 1940s vintage. I bought it via ebay some years ago. It's hard to describe. I do have the manual. Basically it hangs down underneath the engine with the motor pointing up and down. It uses special thin-rim cup-shaped grinding wheels with threaded arbors that are no longer available and wear pretty fast, so you want to be careful and not over-do it. If need be, you can use a smaller wheel and move it back and forth to do a wider journal. A rail assembly bolts to the bottom of the block using the oil pan holes and that keeps the grinder aligned square to the crank. The business end of the grinder has a hook that hooks over the top of the rod journal so that as the crank rotates, the grinder moves up and down with it while the journal moves across the grinding wheel. There is an accurate adjustment for the depth of cut. It cuts a bit of a swirly pattern on the journal and the instructions suggest cleaning that up by wrapping some fine emery cloth around the journal with a leather shoelace wrapped several times around that and pulling it back and forth while the crank rotates. I used plumbers-style emery cloth on a roll and didn't attempt to get it perfect, just to wear it felt smooth to the touch.
The equipment includes a small electric motor and a padded frame to hold it resting on the fenders across the top of the engine compartment, and a long V-belt to drive the crank pulley at a slow and steady speed. You must relieve compression on the engine by pulling all the spark plugs or fuel injectors before starting the operation.
It will not grind a main bearing journal in the vehicle because there's no way to hook the grinder over the top of it. There was apparently an option jig to allow you to grind both rod and main bearings in a lathe using this machine. In that case, the lathe was used to support and rotate the crank, and the grinder, instead of hanging down, was pulled upwards above the lathe by a spring-loaded frame. It would not be a difficult thing to fabricate, and I may try to build one some day. The problem, of course, as with a tool post grinder is keeping grinding grit out of the precision parts of the lathe. I have a very old lathe with rusty bed ways that would probably be safer to use it on and would work fine because all the lathe needs to do is hold and turn the crank and provide a square mounting surface for the grinder.
The whole thing looks rather Rube Goldberg-ish and rickety but I was amazed at how smoothly and quietly it runs and how rock-solid the alignment of everything is.
The device is intended for repairing one bad rod bearing, not for doing a general overhaul of an engine. This was apparently common work back then. If your other bearings really are scored or burned, you'll probably want to overhaul the whole engine. If it was me, I'd just plastigage all the bearings, mike the journals, and replace them either with new bearings the same size as the ones that were in there, or if they are slightly worn, with slightly undersized ones if they're available. I know for some engines you can get bearings that are .003 under-sized which are intended for freshening up a lightly-worn engine without grinding the crank. Obviously you'd need to make sure there was enough wear that you'd still have adequate oil clearance with the tighter bearings. Most likely, only that #6 rod journal is really scored and in need of grinding. At that point, you'd take it down until you had all the scoring out, mike it, and then keep going to the next tighter standard-sized bearing plus oil clearance.