[23] Brianator's "Silver Bullet" ~ Super Stock Race Mower

#Buildoff2023

Well, it looks like it's that time of year again for me to take another broken down old tractor and breathe some afterlife into it! I want it to be different from my others though...

What I'm thinking is...



So I'm going to take most of this "stuff" plus more "stuff" and turn it into a stripped down and dirty little race tractor!



The plan is to build it with flexibility in mind so I can tear it up on grass, dirt, ice or pavement, maybe even drag race and drift it! There's no racing clubs around here but I'm hoping to find a open class race or two to take it to and see what kind of trouble I can get myself in to! Lol.

I'm going to use USLMRA prepared chassis rules as a guidleline so it's close to being a legit racer and in case the opportunity to race ever arises it shouldn't take much to pass tech, from what I've read this MTD (tunnel) chassis is a very popular choice on the race track! Visually I want it to look tough and have a ThunderCar/Super Stock racecar flare and spirit!


Here's what I'm thinking:

~ Reinforce the tractor while keeping weight savings in mind.
~ Slam it to (or close to) the class limit of 4" from the frame to the ground.
~ A custom front axle and direct steering will be needed so I'll build them from scratch.
~ Lower the bodywork and seat.
~ No electronics aside from the ignition/kill - pull start only!
~ Build the original, single speed Peerless 910 (FNR) good and strong.
~ Get my 11hp Briggs and Stratton "KoolBore" figured out and running!
~ Shave weight wherever I can.
~ Give it a racecar appearance package!
~ Hit 35MPH!

*Plus More! *


This should be a blast to build and drive when it's done!


Approved - Jan 1, 2023 MightyRaze
Withdrawn - July MR

[adm]Welcome to the 2023 Build-Off.[/adm]

Good to see another racer in the build-off.

Now that I am home.  I was a little nervious approving.   That sign is a bit hard to see the password.  I could see it zoomed.  LOL, You're good to go!

Lmao. Ya there is a definite loss off quality when uploading, in the original I can zoom right in and read it no problem.

There I fixed er up so you can rest your mind. Lol

Brianator wrote:

Lmao. Ya there is a definite loss off quality when uploading,  in the original I can zoom right in and read it no problem.

There I fixed er up so you can rest your mind.  Lol

LOL, I've got my eye on you.  Trying to keep me on my toes are ya. 

Well I've been doing some thinking on this, more specifically the rear end. I feel if I build the FNR to hit the speeds I want that she'll be a dog off the line and that ain't cool so I think I'll probably go with my original plan which I never mentioned... putting the 3 speed MST203 from The Warhorse in it! Having selectable gears I think is going to be required and it's already oil filled so if I add a solid axle, bearings, a vent and a grease zerk on the input shaft I think it will be a winning combination PLUS " 3 speed racing tractor" has a nice ring to it doesn't it!? Goes along nicely with the Super Stock vibe I want to protray too!

Before I get TOO crazy with that I will fully build the FNR (solid axle, bearings and gear/chain) to get it ready for transplanting and use this rig as it's test chassis as well as a way to test this chassis! With The Warhorse having the VariDrive (and in decent working order) I'll still have full control of the speeds but I hate the swing shifter on it so I'll have to make my own.

It could be a few weeks before I run into town for supplies as my parts list isn't complete enough yet to make it worthwhile but I've had some parts appearing on my doorstep with more on the way and I figure chassis prep and modification will keep me busy for a bit so ya.  Lol

I'm really excited to build this into a little ripsnorter!

You going to slam it down to the ground?  I know many racing circuits have ride heights.  I know yours if probably more for fun.  Just curious.

4" frame to ground and 2.5" cutting deck to ground seems to be the gold standard and I'm planning on getting it pretty darn close AND with some adjustment. Yes more for fun but I want it to be as legit as possible, I don't want it to just look like a race tractor I want it to actually be one and hopefully a competitive one! You never know when opportunities will arise so always be ready! Lol

A couple years ago there was a one season race circuit for mowers.  Only seemed to be about 3 people in my town racing them.  Then they vanished.  I was hoping it would grow then I may have been tempted. Nothing now. Not sure of their rules.  I think they also had the 4" frame height as well.  Then all this back stuff happened.  I've not looked into it since.

[mod]I'm abusing my ATLTF superpowers to bring you this important message! But seriously this is kind of a big deal! Lol[/mod]


The tractor gods must be smiling upon me right now because I've captured a unicorn...
Please note the INTERTANLLY BALANCED CRANKSHAFT and COMPLETE LACK of block destroying SynchroBalance plates in this vertical shaft Briggs and Stratton aluminum blocked flathead!! I've merely read rumors of their existence...

This is a "got-it-from-salvageyard-this-past-summer-for-$10-just-because-why-not-stripped-down-parts-motor-that-I-decided-to-open-up-tonight" kind-of-shock that I didn't expect to ever feel.

I'm not sure what else to say right now!

Good score.  I'm not up on those engines, but I will say that huge balancer is a pain in the rear.

A huge pain in the rear and would've always be a worry in the back of my mind. There's a billet connecting link for them you can apparently get but I can't find a listing from the supplier and not sure they ship to Canada either but regardless of all that it looks like I have an excellent engine to turn up the revs some!

Any money it would've cost to either overbore the other engine or outright replace it (and still be stuck with the counterweights) will be better spent on a 12.5hp AVS rod (for strength), new rings and full gasket kit!

The bore is nicely glazed which I understand is desirable in a KoolBore block and is in pretty darn good shape with almost no wear and only very minor scuffing, I'll post some pics of that later!

Well, I looked over the engine some more after work then tore it down but I don't want to jam up my build thread so I'll make a separate thread for it then post a link here!

If this engine is going into the build-off rig. I see no issue with all the engine talk. There is a long time left and it helps to document the build beautifully. But that is just me.

If all goes to plan it will but look at what happened with the 11hp... that's my worry and I'd like to keep the focus on the tractor itself because that's where the real magic will be!  Motors come and go! Lol.

This thread will get an engine related update eventually and when it does I'm hoping it will be this one because it will fit the build theme really well!

A seperate thread for it has better potential to help others find info as well, I've had a bit of a time myself...

I've gotten enough parts together to at least show something finally, there's a couple more small things still on the way but most of the rest I'll have to get locally (mostly supplies).

Clockwise from the top left:

~ 1/2" rod ends w/hardware for the steering king pins.
~ 1/2" ID × 1-1/8 OD bearings I WAS going to use for the steering spindles, before I decided to go with rod ends for KPI/camber adjustability. I'll try to use them somehow.
~ 5/16" rod ends for the clutch linkage.
~ Quick release steering wheel hub (3/4" weld-on).
~ 3/16" fat headed aluminum body rivets.
~ Ignition/kill switch.
~ Mechanical brake caliper (from a mini bike I think).


I have 2 LH and 2 RH 3/8" rod ends (plus a LH tap and hardware) on the way for the steering drag link and tie rod so they're easily adjustable, 1/2" aluminum tube is one of the things I'll need to get locally to make them. I'm trying to keep the weight down best I can while keeping everything strong.

I'm not sure what the tractor would've weighed stock but hopefully under 300 lbs which is in bathroom scale territory so I can try to figure it out and keep track of the start to finish weights!

Teardown has begun!



I want to have this completely stripped to a bare chassis tonight so I can start measuring/planning what to cut away and frame reinforcements.

All parts not used for this build will be shelved as spares for The WarHorse!

Mission Accomplished!



While I was at it I decided to start welding the corners and the frame pieces together as well to stiffen it all up. There's still more to do but this is a great start!


The way I figure it a few welds and some aluminum rivets throughout the chassis and body to replace the hardware should shave a couple of pounds, it's not much but every little bit helps! A couple of pounds here ~ a couple of pounds there and it's starts to add up right!?

The front of the frame which is also the axle mount is already tipped back at a 13° angle so I left it alone, 10° of positive caster is supposedly the magic number and I'm sure that 3° difference will be well within the range of adjustment on the axle end plates.

For once I'm actually starting from scratch! Lol

I've completed a quick mock up to start figuring out the rear axle location for frame to ground height and how it will translate into the front axle/spindle height. It's all looking really good by using the original fender pan location which is great because it means I won't have to modify anything for it to reattach to the footboards! It will also keep it very stock appearing which is something I'd like to keep with...think Super Stock!

By losing the seat spring and putting a seat right on the fender pan it will be about 4.5" inches lower while keeping it above the tops of the rear tires and over 13" from the ground to the bottom of the seat which is part of the rule book. Steering wheel height isn't terrible but I'd like to get it a touch lower so the hood will sit pretty level once the grille is lowered, as of now it will sit at a noticeable angle and that's not going to look good when the side panels go on. Based on the 3 piece dash design this is going to be really easy to do which is awesome!

Looks like it's going to come together really well so I'm pretty happy!

Well, after mocking it up and seeing the vision I went to town on it for most of the day! Need that grille and hood dropped for the right look but the dash had other plans...

So I trimmed the lower bit even which dropped it 1-1/8"...


...but it wasn't quite enough! When I dropped it I also pushed it ahead into the side plates (3 piece dash) and what that did was perfectly realign the steering shaft to go at the same angle and through the same holes in the dash and in the chassis which are in the rule book so I couldn't cut any more away from the bottom.


No problems though, there's plenty of steel up top to section out of there!


The sides didn't line up but that was an easy fix.

Here's the before after!


I decided that's as far as I'm going with the dash and I'll just have to do my best up front and hope for the best. Turned out awesome if I do say so myself! That's about a 2-1/2" body drop.


I didn't want to mess with the fender pan but it didn't look right anymore with the body lowered so I trimmed away just enough to sit it flat on the frame so I could start playing with spacing. Clearance to the rear tires will be tight so I can't set anything in stone yet but in the above picture there's a 3/4" piece of plywood under it and I'm digging it!

That was a productive day!

Nice work on the dash. Not sure if asked before. What kind of welder do you use? If I were to do that, it would vaporize the metal no matter where I put the setting on my welder. Then again it is nearly 64 years old. HAHA.

Just a 110v/100amp flux core but even I have to be careful or I could burn through it. One thing I can say is that it's not flimsy steel, you couldn't flex that dash by hand that for sure!

I got a little bit more done today and another mock up.

I slotted the chassis for the rear end, I still need to verify the MST will fit the same then make mounting plates for it. I'd like to make them adjustable so it may take some time to come up with a design and put it into action but it should be worth it!


Second mock up with the rear axle in place and a 2x4 simulating the front axle. I tried to recreate the photo angles best I could.

It turns out I may have to leave the fender pan at stock height, the tires were touching it with it spaced up 3/4" but the seating position really doesn't feel too bad at all! I'll definitely need to flare the fenders, I had to tuck the tires in about an inch to set the fender pan back down!

One more beauty shot and I'm done for the night! She's sitting about 5" frame to ground in this pic and I'm liking it! I'm loving the body drop too I think it looks great!

Well no physical work done today but I did put this together to illustrate the difference between before and after the body drop.

I also got 5/8" spindle bolts with castle nuts, 1/2" kingpin bolts and the material I need to make the steering shaft, spindle barrels, drag link and tie rod.

Then I designed the end plates for the axle I'm building, I've given it +/- 15° of caster adjustment which is probably way more than I'll need. Now that I have that sorted out I can start figuring out the measurements to cut the spindle barrels down to, I'll use about 1" worth of washers so I have some height adjustments I can make. I'll need to completely build and assemble the front spindles with end plates installed on wheels so I can figure out the width of the front axle.

Lots of work to do, the front axle will be a project on its own and is something I'd like to tackle sooner rather than later!