FatJackDurham 318 #1 Posted July 21, 2018 I found a 520 H for $350. THe guy had dumped $800 into the engine last year at a shop, then tried to change the muffler himself and sheared off the bolts. Despite years of great service, he felt he couldn’t put any more money into it. He was selling it with a REALLY nice deck and snow blower, but I only wanted the tractor. Any one wants a nice deck, no rot at all, eyeball the Vermont CL next week. Anyway, I think I just need to drill out the bolts and helicoil the holes to attach a new muffler. Any suggestions are welcome. Pictures later. It’s definitely used, bits of rust, but he says its fully functional. We’ll see. Be a good score if it is. 4 2 Share this post Link to post Share on other sites
Pullstart 58,797 #2 Posted July 21, 2018 Need pics! Congrats on the steal, if there is enough stud flush or sticking out of the block, give it a good whack with a punch to shock the threads, then weld a nut to whatever is left of the stud with as much hot penetration as you can. Let it cool, shoot some wd40 or oil of your choice on then try to back it out. Might be quicker and cleaner that drilling it out... 3 1 Share this post Link to post Share on other sites
cleat 4,896 #3 Posted July 21, 2018 Drilling a steel bolt out of an aluminum block is going to be difficult. Welding a nut to the existing broken bolt as pullstart said might be better. If you do not have a welder it might be worth taking the engine to someone who does. 2 1 Share this post Link to post Share on other sites
WVHillbilly520H 10,369 #4 Posted July 21, 2018 Not an Onan but as couple years back had half a dozen exhaust manifold bolts rust through and cause a nasty rap/tap noise on my Chevy Trailblazer 4.2L inline six with aluminum head, I did the "weld a nut" and got all but 1 (way under the cowl) out that way, Jeff. 1 Share this post Link to post Share on other sites
FatJackDurham 318 #5 Posted July 21, 2018 THanks all. Bolts don’t stickup enough for me to weld I think. If I had a MiG and chord stick the wire through the nut, maybe, but I doubt it. I can try heating with a torch first and then maybe use an extractor. The fact that it’s aluminum is interesting. That means there is definitely not rust bonding.... I agree, this aims to be a sticky situation. 1 Share this post Link to post Share on other sites
WVHillbilly520H 10,369 #6 Posted July 21, 2018 1 hour ago, FatJackDurham said: THanks all. Bolts don’t stickup enough for me to weld I think. If I had a MiG and chord stick the wire through the nut, maybe, but I doubt it. I can try heating with a torch first and then maybe use an extractor. The fact that it’s aluminum is interesting. That means there is definitely not rust bonding.... I agree, this aims to be a sticky situation. There may be no "rust" but there is the disimilar metals "corrosion" witch sometimes is worse, yes they do look broken off to far to weld, be very careful with the torch, Jeff. 1 Share this post Link to post Share on other sites
JAinVA 4,617 #7 Posted July 21, 2018 Jeff is spot on about dissimilar metal corrosion.I doubt that heat is going to be of any help.You are probably going to have to drill and retap. 1 Share this post Link to post Share on other sites
C-101plowerpower 1,589 #8 Posted July 21, 2018 if you have the time this appears to work first one doesnt, second one does Share this post Link to post Share on other sites
FatJackDurham 318 #9 Posted July 21, 2018 Speakin’ o’ welding.... IF does it damage any components to tig or mig weld the engine with everything still connected? Wires and such? I assume I’d just connect to ground to a bolt or something on the engine block, but I was just curious if all that current could damage anything. I know the electricity should take the shortest path to the ground wire, but it still skeeves me out a little. Share this post Link to post Share on other sites
Pullstart 58,797 #10 Posted July 21, 2018 I rarely disconnect a battery to weld on automobiles, but I probably should for safety precaution... but so far it’s been just fine! Share this post Link to post Share on other sites
Turftech 82 #11 Posted July 21, 2018 I have had good results with this method: Try soaking with your favorite penetrating oil. While they are soaking for a day or two. Locate a set of left hand drill bits. The idea is if the bit grabs the broken bolt will wind itself out. Remember drill motor set counter clock wise! Share this post Link to post Share on other sites
johnnymag3 2,423 #12 Posted July 22, 2018 You have your work cut out for you, but it will be fine when its over. Dissimilar metals are far worse than rust, as previous people have mentioned......take you time GOOD LUCK to you.....breathe deep............. dont surrender Share this post Link to post Share on other sites
ericj 1,576 #13 Posted July 22, 2018 might want to try and use a drill press, which means you have to disassemble more of the motor, but the you are less likely to have the bit walk on you as compared to free hand drilling. Good luck eric j Share this post Link to post Share on other sites
RJR49 121 #14 Posted July 22, 2018 You MUST use a center drill. A drill press might work but I would beg someone to lend a Bridgeport type mill. A hand drill WILL NOT work. An endmill would be better. In any case, even with a Bport you will need to fixture it to hold it vertical. Check out what a pro would charge. It might be less than you think. If your in Connecticut I might be able to help Share this post Link to post Share on other sites
bds1984 1,377 #15 Posted July 23, 2018 I second the center drill. Those will not "walk" like a split-point drill bit. Also, if there such a thing as a cobalt, left-handed bit, use that in a drill press or milling machine and you're on the right path to getting this 520 back among the living. Share this post Link to post Share on other sites