Engine Swap Research
 

I have been reading the forum trying to gather info on a possible engine swap. I have a 108 that I am going to use as a yard tractor for pulling my wagon,leaf sweeper and disk and eventually plow with. It has a 12hp kohler with a bad carb and possibly some other issues. I have 2 18 hp briggs opposed twins on other tractors that I am considering putting into the cub 108. I have read that I will have to cut the frame but I have been unable to search and find a thread with more details. Everyone please give me thoughts and ideas other than rebuilding the stock engine. I am looking for a "restomod" type set up for this cub. Thanks so much for this great forum.

I am also interested in this type upgrade, ...........

Maybe someone could chime in with knowledge as to whether that extra horsepower could be "usable" in a gear drive tractor??

My 108, with a 14hp didn't seem to ever run out of horsepower doing drawbar/hitch type work. I felt the tractor was more traction limited.

I think the 18hp would be great for mower work, when the grass is too high or thick!!

I also agree that 12-14hp is plenty. My thoughts were I really like the sound of the 18hp twin, it would be something a little different and I have 2 of them already I can use. I dont want to get into other brands but I have 2 Craftsman GT6000 I currently use as "play" tractors and I thought I would like to fix the 108 and get rid of them and only have the cubs. I read on another thread that the 108 stock drive line should be OK up to about 14hp so I am wondering how it would handle 18HP? I have the cub partially torn down but before I started tearing down the Craftsmans I wanted to have a solid plan for the swap. I also have a new set off ag tires and 55 pound wheel weights to go on the Cub to help with the traction issue.

A K321 is probably as strong as one of the newer 18 hp V-twins...the newer engines don't have as much torque. 14 hp and above I'd recommend a stronger clutch spring. 12 hp is more than enough for what you say you'll be doing with it. You'd have a hard time putting 18 hp to the ground anyway. These tractors are light enough they will run out of traction long before they run out of horsepower.

Interesting points Matt I've always wondered about the torque output specs of the k321 and kinda wondered if it were to let go that I know some locals that have put the vanguard Briggs engines in their cubs and the obvious is the sound pretty cool but assuming they are shorter stroked less torque would be made and what hp engine would have to be put in to equal the torque of the 14hp kohler! They state that the right one bolts right up but they have several different models and several with different vanguards! I don't believe they are on here but live real close to iluvtrucks and some others that know them may know the specifics. I will say that they are into a little everything showing, pulling and using them and they have bone stock to different fueled ones! I was to stunned to take pictures when I saw there collection!

Im not necessarily looking for more horsepower its more of I have the engines,I like the way they sound and it would be something different than a stock tractor. If I had a running ready to go 12-14 hp single cylinder Kohler I would definitely consider just dropping it in. The two craftsman do the job fine and they already have hi/lo range and sleeve hitches. My thoughts were I like the cubs better and I would part the craftsmans out to buy the hitch and creeper for the 108. Currently I am still at the point of will the 18hp engine fit without major modification issues. ajcombs I am not using the Vanguard mine are the older style model 422437 engines I wonder how they compare to the Vanguard as far as fitting in the cub.

Torque curves / comparisons
 

K321 torque Here you go guys .... torque curves for kohler and briggs 18


I found a Kohler K series graph chart in a book by Paul Dempsey which shows:
K301(12hp) peak torque 22.25ft lbs @2200 rpm.
Also max. brake hp is 12@35-3600rpm but torque is 17.5ft lbs. at this point.

Others interested are:

K241(10hp) peak torque 16.5ft lbs @2400rpm, and max. brake hp is 10@3600rpm torque is 14.5ft lbs.
K321(14hp) peak torque is 23.5ft lbs @2400rpm and max. brake hp is 14@3600rpm torque is 20.5ft lbs.
The BIG K341(16hp) peak torque is 28.25ft lbs. @2600rpm with max. brake hp 16@3500rpm torque is 23.5ft. lbs.




Torque specs for 18 HP
Horizontal Shaft
Vanguard engine




Number of Cylinders 2

Gross Power: (kW/HP) 13.4 @ 3600 / 18 @ 3600

Peak Gross Torque: (Nm/ft-lbs) 38.9 @ 2400 / 28.7 @ 2400

Bore: (mm/in.) 72 / 2.8

Stroke: (mm/in.) 70 / 2.8

Displacement: (cm³/in³) 570 / 34.8

Oil Capacity: (l/oz) 1.7 / 56 (with filter)

Dimensions: (LxWxH) / (mm/in.) 392 x 404 x 438 15.4 x 15.9 x 17.2


Rgds, Bryan

Thanks scgtguy, K301(12hp) peak torque 22.25ft lbs @2200 rpm. 18hp Briggs Peak Gross Torque: (Nm/ft-lbs) 38.9 @ 2400 / 28.7 @ 2400. That answers that question. Now can the drive line handle the apprx. 16.4 additional torque in the 2200-2400 rpm range and will my engine fit in the 108 with out having to do MAJOR fabrication. I want to be able to drop the engine in,change the necessary wiring and hook the drive line back up. I don't mind to trim some metal or rebuild the clutch but I don't want to have to completely re manufacture the whole tractor.

vanguard swap
 

Glad to, i've got one operating in my 1450 wide frame but its a hydro ... works out well. Not sure on your drive line with the manual trans ... maybe someone else with manual drive lines might shed some info for you.


good luck !

Bryan

Yea I think the frame width and drive line are gonna be major issues in a swap. I may sell all three tractors and just try to find a cub with a larger engine or at least running ready to use.