7hp Briggs in 76
 

I been asked by a friend to freshen the 7hp Briggs in his model 76 Cub Cadet. The B&S is a model 170700 and in looking at the parts breakdown on the cub site, it shows an IH # of 539837-R91 for the connecting rod. Is this unique to this tractor? Why not a Briggs rod? Before I get in too deep, I'd like to know for sure what is available to overhaul this engine. oversize pistons are available, but the IH connecting rod is NLA of course. The crankshaft is shared with other B&S motors of that series so I guess I could find one if needed. Has anyone had to deal with this con rod issue?

Probably no one on here that has had them apart. That tractor wasn't a super popular one for restoration. Plus, usually they have long ago been repowered with the B&S replacement engine.

The crankshaft is listed as an IH part number. Probably because of the length and size of the PTO end was set by IH, and thus assigned an IH number. Now, the journal could possibly be a different size.... but since it uses a standard B&S piston, I'd say the stroke is the same. It's likely that a common rod will fit, but possible it may not. If that is the case, I would grind the crank to whatever size you need it to be, then buy a new rod (as it's likely the length pin to pin is the same) and either have the rod sized to fit, or have a bearing insert made to size it to the crank. It sounds expensive, and while it is more so that just installing a rod, you might be surprised how much it costs. All that work for a B&S motor in a non-typically restored tractor..... guess it all depends how much your buddy likes his IH. :biggrin2:

Only real way to know (as I'm sure you do) is to pull it apart and check it out. Get your journal size and check it against a B&S book and see what works. :beerchug:

Thanks Jon. I kind of figured that it was something along those lines of being a special mod for IH from Briggs. I tried to talk my friend out of doing anything with a less than popular Cub, but there is a strong sentimental value. His dad bought it brand new and it was the tractor he learned to mow lawns on. His dad always wanted to "get it cleaned up" but never did. He just recently passed away. My buddy wants this to be a memorial I guess. I asked about repower and was told he wants to keep it as dad bought it. So it looks like a big machine shop bill is the next step.

Sentiment is a powerful thing.

Like I said, pull it apart and check the crank journal diameter. If there is a difference, I'd say that is where it will be. It's likely that if the stroke is different, or the rod was a different length, then the piston would also have an IH part number, but it does not. Journal size is the only possible difference that makes sense. May also in fact be the same as a non IH motor, just uses that part number because of the tractor specific crank. With this older stuff, it's anyone's guess. But we can make some logical assumptions, and use calipers and mic's to learn a lot, lol. :beerchug:

Doc, cub price book says to use BS-295839 for the rod which is STD.

Sounds like a cool project. The LT's might not be as popular for restoration but they sure look good when they're done, I did a 111 for my son a few years back. Keep us posted on the project.

I have had a few Biggs engines apart. First thing I would do is go to Briggs and Stratton's website ( https://shop.briggsandstratton.com/us/en ) for parts. I have found out the best thing for engine parts and engine info is go to the manufacture that made the engine. I would purchase parts from a local small engine dealer.

Another site that may be able to help is I Save Tractors (http://isavetractors.com/)

Briggs used to have rebuild kits. Not sure what Briggs has now for the old engines.

Thank you gentlemen for the guidance. As I get into this project further I'll start a post with some pictures. I just picked up the little bugger and brought it to the shop this morning. It needs a good bath and then pull the engine.

X2 on this advice. The IH dealer dad worked for carried Kohler, Wisconsin, Briggs, Onan, Robin, and could even get Tecumseh. The always bought engine parts from the engine manufacturer, not the equipment manufacturer. Should be cheaper as well.