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.

You're looking at those numbers wrong, by those numbers the 18hp Briggs puts out 38.9 Nm, that's Newton Meters. So you really only gain 6 ft-lbs, not 16.

You are going to have to cut away quite a bit of frame to get an opposed twin in there I would think. You will have to figure out a way to reinforce the frame. I also think you will be hard pressed to make it a bolt on affair.

I think a v-twin would be easier to fit in if you are dead set on something other than a single cyl. kohler.

I personally would take the Kohler. Rebuild the carb, mill the head about .030 and get your ignition in shape and it will put out some good horsepower!

Not trying to rain on you parade, but I think you would spend more time and money trying to put the twin in.

I love to mod stuff, but its always and one step forward and two steps back!


Good luck with your project and post some pics! :beerchug:






Randy

Just like to put my 2 cents in. I use, pull, and enjoy cub cadets. I have done a briggs vanguard swap into a 1000 frame for a guy and was not that bad and frame did not have to be hacked to heck, some cutting but looked pretty good when finished. In my opinion the vanguard vtwin is one of the smoothest running engines out there. A 14hp Kohler will not even hold a candle to a 14hp briggs vanguard in pulling. I ran one for a few years against built 301 and 321 governed and had no trouble in being in the money almost everytime out. I love the old flatheads, but these new engines are awesome for someone not concerned for originality. Thanks, Just thought I would chime in since I have a little experience on this issue

I have been following this tread also, I have a cub cadet 1000 and I have a little Kubota diesel motor that puts out about 22 horsepower. I was really thinking about making a custom puller with these but will the drive train be able to hold the power? Are there really limits to the legendary cubs?:biggrin2:

vanguard swap
 

They do work out well in a swap ... mine required no cutting of the frame etc. but one the side panels will not go back on my QL. Engine runs very smooth and uses aprox. half the fuel of the k that came out.

Dang that vangaurd looks good in there! Looks almost factory nice job.

Does the pto still operational when the swap was complete?

pto / swap
 

Yes...stock pto in place...but you have to fab a mounting plate to mount.
also have to fab a motor mount to level drive shaft and fab a drive shaft fly wheel coupler......


B.

Great info so far BUT my engine is not the Vanguard V twin mine is the flat opposed style Briggs twin. I did some basic measurements with the engine still in the Craftsman. The frame width of the Craftsman and the Cub are pretty much identical. The length needed to clear the engine on the Cub is fine. The frame rails in the Cub are high but at a basic glance they would need only minor trimming if at all. It does appear that the motor base plate will have to be modified to the Briggs and the drive shaft height is about a 1/2" difference between the two engines. Please keep in mind these are quick at a glance measurements and not exact. The Briggs has an electric PTO so I could still use the deck and attachments. At this stage I think the major issue is fabricating the fly wheel coupler.I have the Cub 2284 to mow with so I am trying to decide whether to just keep using the Craftsmans for yard work as they already have sleeve hitches and hi/lo range and sell the 108 or sell the craftsmans to fix up the 108 the way I want to use for yard work.

scgtguy,
What are the frame measurements on the 1450 as compared to the 108. They look identical in shape from your picture.

Wideframes
 

not ever having a 108 myself I don't have hands on experiance .... but they are both wideframe tractors, I assume they would be the same.
If you take a read at this the differance is starters, charging systems and the like.

http://www.xtrememotorworks.com/Cub_cadet_History.htm

Bryan

To put any horizontally-opposed twin into a WF, you'd need to cut the frame quite a bit. Notice how the 82 series frames are made as not to have this problem.

I have seen this done a few times with different brands of engine. The end result is the same for all- much of the frame was cut away, weakening it badly. You'd also destroy the resale value of the tractor. I've seen a few modified like this on ebay and at auctions; they don't bring very much money.

I would either look for a V-twin or just stick with the original engine, the latter of which will be more than capable of doing what you want. Those B&S flat twins are inferior to the K-series Kohlers in many ways, too.

Matt G, Im not concerned with resale I bought the tractor to use and 108s are really common it seems, so collectors value would not be that high. Again the reason for using the 18hp Briggs is because I have those and I cannot justify the prices Im finding on used kohlers or the #26 carb I need to even get my engine running. After researching and getting a lot of input from you guys (THANKS!) Ive about decided to sell or part out the 108 and the 2 Craftsmans I have and just buy another Cub already running.

Alright I did some more measuring and I resolved some questions. A flat opposed Briggs has approx 3" from the engine base to the bottom of the cylinder. A cub 108 frame measures apprx 5" inches in depth to the base. So with that said apprx 2" of the frame would have to be notched the length of the cylinder head so MattG is right on that a major section of frame would be removed and that would cause weakness. Of course none of this applies to the Vanguard V twins. Now for my part I dont think it is feasible or economical to attempt this engine swap so Ill go to plan B and sell or trade some of my tractors and see how things turn out to see which way I go from here.

Quick Update
 

Thanks to forum member Dave the old 108 is up and running with a rebuilt carb. I sold the Craftmans and the money is buying tools and Cub Parts. The 12hp Kohler sounds good and hopefully when the weather breaks Ill take it for a spin around the yard.
http://i1120.photobucket.com/albums/...1-21154608.jpg

You got a good looking 108. :beerchug:

That 108 looks to be in real good shape. While your waiting on better weather, try some rubbing compound and wax. You will be amazed at what you may see. :beerchug:

the frame only needs some minor trimming the biggest problem is the gas tank to air filter clearance

I would not consider that 'minor' trimming...a lot of the strength of the frame has been lost.

I agree with Matt completely. the reason these Cubs are still usable 30, 40 and 50 years later is because they were engineered for strength and quality of product.
Go look at the modern box store units and you will see cut down and flimsy components... now we engineer too many things with "planned obsolescence" and "warranty periods" as the goal.
We do have some better metallurgy going on today, but more often than not unfortunately it is all about bottom line marketing.

I'm guessing that old Cub will survive its transplant and serve you well, but the strength and integrity of the frame truly has been compromised...

i dont believe that i will ever have a problem with the frame being to weak because of the material i removed but if i do Matt you can have every cub part that i own.

That top ridge that you cut off gives the frame most of it's strength. It's your tractor and as long as your happy that's all that matters.:beerchug:

I agree with Matt and jpackard56.

The engineers at IH Cub Cadet wouldn't add the extra cost into the frame if it wasn't needed. You may be saving a few $$$ by installing the Briggs. Good luck finding parts fot the Briggs.

I would not bet money either way!! That flange turns the frame into a channel, which is stronger, BUT, it adds good manufacturing appearance at almost no cost since they are stamping the frame anyway!!

The engine was a feature the prospective customer most likely would look at, the IH guys had to make that area look G O O D !!

The frame has a cross brace welded in at the foot rests that really stiffens the frame, possibly negating the need for that flange.

Look at how short the channel height of the frame is on later models of this tractor!! This modified one is still taller than the new ones.

Time will tell, I'm sure we will get a report if a failure occurs.

IMHO!!

You have extra cost in the punch and die because of the upper lip on the frame. My 70 and 100 have a factory brace welded in sde frame rails. Wide frames and Quiet Line don't have that brace. The radius on the top of the frame rails stengthen the frame rail enough so you don't need the welded brace.

Well, I say to each his own but after seeing the actual cut outs on the frame Im glad I followed everyone's advice and kept the K301 engine. Im no engineer or fabricator but I think I would weld some braces in place if I had went that route. However if I ever find a more "bolt in" twin set up I would be tempted!