Racinbob 10,414 #1 Posted April 3, 2014 The K91 engine on the Suburban 400 I just got has had the crankshaft replaced with a tapered shaft because that's what the PO had on hand. The pulley was welded on. I'd like to replace it with a straight shaft and the correct pulley. The seller has the original crankshaft and I'm picking it up tomorrow. The damage from spinning the bearing is pretty minor. I have heard of having it turned down a bit and fitting oversize (or is it undersize?) bearing. The cost of a new crankshaft is out of this world and I'm leery of buying a used one. I would spend the bucks if it was my worker but this 400 will just be a toy and not worked much. Has anyone done this? If so, by who? Thanks. Share this post Link to post Share on other sites
oaktown1987 82 #2 Posted April 4, 2014 Some shops will weld the the journal then turn back down or u can have the crank turned down and rod and have a bearing inserted in rid Sent from my iPhone using Tapatalk Share this post Link to post Share on other sites
MalMac 1,328 #3 Posted April 4, 2014 Technology has come a long way on the repair of crankshafts. There are some different options for you out there. The big problem is the cost of the repair is really up there, at least that has been my experience on big motors. I think your best bet is just keep a eye open for another crank. Also your cost in repair will vary occurring to whether it was the journal or a main bearing has spun. If it's a journal, and it's not too far gone they can be turned down and bearing insert of different size can be had to match up a new rod. If it's a main, then your looking at some type of build up then turning back down to spec. and possible re-heat treat the crank. to relieve any stress put into it from welding on it. I am by far no expert in this, maybe someone will chime in here with some knowledge of crank repair. Congrats on your find Bob and sorry I could not meet you when you were right up here by me. Share this post Link to post Share on other sites
KATO 115 #4 Posted April 4, 2014 They do make a .010 thou undersize rod for the K91 and you can have the crank turned down .010 with out any trouble ...but if it wont clean up then you may have to look at other options as stated Share this post Link to post Share on other sites
WH nut 553 #5 Posted April 4, 2014 How bad is it. Most of the time its just aluminum transfer and that can be cleaned off with emery paper. Share this post Link to post Share on other sites
Racinbob 10,414 #6 Posted April 4, 2014 I'm hoping I get that lucky WH fan. I'll be picking it up this morning and will know more. At least having it gives me another option. KATO, That's exactly what I heard. I priced new crankshafts at over $300 and I'm not wanting to do that. But I'm a bit afraid of buying a used one (Ebay) for fears of having issues with it. MalMac, I would have loved to be able to meet you when I was up there. I had hopes of coming home with a tractor loaded. I did meet dw753 because he was just 5 miles from the kids house. I would have scarfed one of his had it not been for priorities with my daughter and needing to get her to Minnesota. My son in law was working a crazy schedule and, with no ramps, I would have needed him to help load/unload. It could have been possible but I didn't want to add anything more into my schedule. Thanks all for the advice. Share this post Link to post Share on other sites
KATO 115 #7 Posted April 4, 2014 (edited) As WHNUT says it may clean up easily ..,i would try his suggestion first then measure the crank if you have a micrometer or take it to a machine shop and have them measure it. Ive even had them offset ground a few thou if they are badly out of round Works fine as there is usually lots of room above the piston for a few thou more piston height. Since were only talkin .002 or .003 Edited April 4, 2014 by KATO Share this post Link to post Share on other sites
shorts 182 #8 Posted April 4, 2014 I've had good luck just picking at the aluminum transfer from the rod to the crank with an Exacto knife and then a final polish with some emery cloth strips. Use as fine of grit roll as you can find then tear the strips lengthwise so you can get 1 full wrap around the crank journal while polishing so you apply even pressure and keep everything round Share this post Link to post Share on other sites
js5020 111 #9 Posted April 4, 2014 A trick I have used is muriatic acid on the rod journal,, the acid "eats" the aluminum and doesn't harm the steel. Just do it in a well ventilated area and protect your eyes/skin. Easy peasy. Share this post Link to post Share on other sites
Racinbob 10,414 #10 Posted April 4, 2014 Well, I have the crankshaft here at home. The journal is scored some. It looks like it will have to be turned down. I will mic it and check the specs. Now I'm in hot pursuit of an undersized rod. Great advice from all and I appreciate it. Share this post Link to post Share on other sites
