Hi guys, I have an old 70s model Wheel Horse mower, it has a Kohler K181S engine which is an 8HP single cylinder horizontal shaft flathead engine with a cast iron block and aluminum head.
This mower has been parked for ages due to having run the motor low on oil. I decided to pull it apart to fix it and I got to thinking about maybe hot rodding it. Just wondering a few things, firstly how strong is the stock rod and how high could I safely rev it after disabling/removing the governor? Will a Briggs rod interchange? (My dad says this engine has been bored something like .070" over and has a Briggs piston fitted, with the rod reamed out to accept the larger Briggs wrist pin.) What about valve springs, what are the options there? What do you guys think about these motors in general?
The transaxle in this thing is a three speed with reverse, with a strange H (turned sideways) shift pattern and a low-high speed selector. It is driven by a large pulley on the right side and is obviously very low geared. The brake is built into the transaxle, it has a rotating drum on the opposite side of the drive pulley with a brake band that wraps around it. On the back of the transaxle there is a tag that says "Uni-Drive"; gotta look over the thing more closely and see if there are any more markings. Any idea how strong this transaxle is and ideas as to its suitability for racing?
If I build this thing, basically what I want to do is just build a kick a$$ 1/8 mile or 1/4 mile drag racer out of it, but still have the capability of driving it around at part throttle and with decent driveability. I have heard these small engines can be supercharged with a smog pump and I would like to try that. I am also not opposed to running methanol as I believe there could be considerable advantages to doing so. I am pretty well equipped to do most types of fabrication, and intelligent/knowledgeable enough to take on this project, just extremely short of funds so this will all have to be done for CHEAP using whatever parts I can scrounge up or get for cheap.
This is my first time really messing with a small engine but I learn quick so no worries.
Thanks for any help you guys can provide!