Rod broke on this VH70 Tecumseh. Crank is scored but still at standard spec. Can't find a crank anywhere, or a drop-in engine. No oversized conn rods made for this engine. Owner is singing the blues.
Yep, it is blues time.
No cost effective way to rehab an engine that has reached this point of destruction. Even if a good standard sized rod could be had.......it would require a very sophisticated engine specialty machine shop to "build up" the damaged crank journal and then grind the crank to match the rod.
And by the way, it would be "Undersized" rod to correct for having to grind the crank journal to a smaller diameter.
If the owner wants to keep using this tractor it may end up with searching for a used engine (drop in) or retrofitting some other engine to the chassis. (gloom, despair, and agony)
has he spread his tale of woe about the weekendfreedommachinesdotcomforumswheretheantlerheadsallhangoout?
no, not yet
I just spent 15 minutes on MTF and I can't even find a way to post a question. There isn't a single return on a search for a VH70 engine. That forum needs a John Deere brush cutter to clean up all the junk on the pages. At least this forum is organized.
If you have not registered to be a member, you will not be able to post anything, and that is business as usual for any forum worth its salt.
Basically, if you are not already registered as a member you need to take care of that first.
Then you need to choose one of their forums to post a thread (with your question) into and when that page opens on your screen, find a small button on the left about half way down the page that says "Start a new thread".
I finally figured out how to post on the Classifieds, but nothing else yet.
I joined in the beginning. I think my number is 255, but I never had enough time to build up my posts.
hapcoparts dot com there other thing here, but not crank
has rings and parts tree has rod all standard.
Here is a link that might be useful: Ring standard
I had another, different model, 7HP Tecumseh in the barn and I looked at the end of the crank. It appears to be the same except for some machining of the shoulder and keyway. Maybe a machinist could take care of this.
I don't know if you plan to use the entire engine or just try to get a crank for the damaged engine.
If you plan to swap the crank to the defective engine some other things to consider are the cam and crank gears, are they a match?
The bores of the 2 engines, are they the same?
The pistons, do they match as to the wrist pins locations and pin diameter? Are the pistons the same weight?
Connecting rods, are they the same in all dimensions and weight?
The flywheels/fans, are they the same in all regards? If the flywheels are different in dimensions or weight you are probably back to square one.
If weighing, you will need an accurate balance type scale or a very sophisticated analog or digital scale. For that task (if needed) I suggest a well equipped engine builder type of machine shop.
If the things above are a match, and the piston, con rod, and gearing are in serviceable condition............you should plan to use all of those.
If you plan to use the good engine altogether, disregard all that I said above and go straight into rehab with the old engine.
A good machinist should be able to adjust the position of the shoulder and extend the keyway without much trouble.
As machinists say, the worst part is getting the piece set up to work on. I see the use of a lathe for the shoulder and a broach, end mill, or fly cutter for the keyway.
The crankshaft WILL have to be removed from the engine for the work to be done.
And make certain that the crankshafts are as clean as you can get them, machinists usually don't like stuff brought to them covered in grease/dirt and dripping oil. Good luck and happy Thanksgiving Day. :^)
The Tec 3-11 HP flathead manual gives crank dimensions.
It appears the VH-70 "MIGHT" use some of the other 7 HP cranks, since there are several listed in the same specs column.
Here is a link that might be useful: Tec manual
If the owner wants to pursue this, I will take the crank out of the other engine and have it machined, if everything else matches up. I'm hoping that the cranks are alike, except for the bottom part.
The Deere was the wife's grandfather's tractor and it has great sentimental value. The tractor sat in a shed for at least 10 years after his death and it was always a dream to get it running again. They were using it around the house until the rod went. For sitting that long, it was in remarkable condition....especially for a 1973 model. It seems a waste to bury the tractor for lack of a motor.