"648 Big Base" Scout (58" Stroker Motor) Info

Here is a very rare, and desirable Indian "648 Big Base" Scout that's famous for it's success in "AMA Class-C racing". They won Flat-Track championships through 1955. The factory made only (50) of these motors. They had unique cases, cam cover, and flywheels. Today, they are highly sought after!

This motor uses exact reproduction cases made by Dick Holt about 20 years ago (RIP). I modified an original cam cover to accept the later aluminum pump (like 648s), and it uses a new Greer's aluminum pump. The original 648s used earlier Bonneville cams, and lifters, but this motor uses my "Andrews SS2" cam that I developed for Bonneville Land Speed Racing, and a set of my Scout Racing Lifters. The original 648s used cast pistons with a .100" pop-up, while this motor uses Ross Forged pistons with a .150" pop-up. This motor uses new Greer heads that are "flycut" for a .050" squish, and contoured. This motor uses new Carrillo rods, with new races, and bushings. Like the original, this motor uses the light weight aluminum rod roller cages (40% the weight of steel). The 648s used standard flywheels that had the OD cut down to 7.500" from 7.750" for lightness. I am using T&O flywheels, that I helped design for Bonneville Racing, and I did a mod to further lower the weights, while increasing inertia. Of course, the entire motor is entirely balanced, and "blueprinted" to my new specs developed from my many years of abuse, racing "out on the salt". The cylinders are late "Square Base" that were at standard bore, with excellent valve seats. The best set of cylinders that I have come across! They received a 5-angle racing valve job, port smoothing, increasing the intake port entry, and precision boring, and honing.

I used a custom made intake manifold that is larger inside for more flow, and I added a Keihin "FCR41" racing carb. It is identical to the carbs I used on my Twin-Scout setting many new records. They are great carbs! For valves, I use "Manley" extreme duty stainless-steel valves that they custom make for me. The exhuast valves are from "Kibble-White", and are "Black-Nitrided" for extreme abuse. I use Titanium valve spring retainers that I have made. I use a stronger 7-coil valve spring that I designed, and Starklite is selling. They are stronger, and can not "coil-bind" under very high valve lifts. Plus, I shim the springs for an optimum 105 pounds of seat pressure with my shim kit that I sell. The cams, and lifters are "All Mine!". At first, I contracted "Andrews Cams" to custom make cam lobes of my design for me. This motor has the hotter "Andrews SS2" Cam lobes. Later, I decided to have them made via CNC at a high end machine shop near me in Los Alamos, NM. They work almost exclusively for the US "A-Bomb Factory". These are hot cams that make good high end power! The lifters are the same as the lifters that I make, and race at Bonneville. My cams and lifters are a matched package, and can't be mixed with any thing else! I am using new "Spriral groove" push rods, and honed to a perfect fit. I also use Teflon intake valve seals (which I pioneered in 2000). This will stop oil migration to the top end, and lengthen top end life!

I spent a lot of time "Blue-Printing" every single clearance to exact dimensions. The balance job is perfect with a 60% balance factor. The flywheels are trued to almost perfection (thanks to the high quality of T&O wheels!). I use custom .050" Copper head gaskets that I have made by "Cometic Gaskets". I gave up on factory head bolts long ago, because they strip out the threads all the time. I have repaired SO many stripped threads in Scout cylinders in the past. Instead, I make stainles-steel studs that are tapered at the bottom, to pick up EVERY thread. These studs have a screwdriver slot on the top, and they are number stamped on the bottom, so they will alwys go back in their proper hole. Above, I use the early beveled head bolt washers, and then "ARP" Grade-10, 12-point "Flange" nuts. Now, you get a much more accurate tourqueing, and you never strip another thread! I also use a Drive-Shaft Seal, like the 1952-53 Chiefs used. It holds all the engine oil in the motor.

For an ignition, I am using a new "Joe Hunt" magneto. It has the very best mounting system. It mimics the original distributor installation with the original advance brackets. But, I don't believe in using the advance/retard control on "Hot Rod" Scouts. It works best if you use a bolt to lock the ignition timing at 30 degrees BTDC all the time. It makes a more powerful idle for stronger "normal" take-offs. Plus it makes the cams really "Talk" at idle.

Some recomendations: For an exhaust, I recommend a 2-into-1 system. The original header works well, then you need to add a 1 5/8" tail-pipe that goes all the way back to the rear of the back tire (slash-cut end!). I have my own dyno, and I have spent a lot of time tuning pipes on a few racing Scouts. Short pipes don't work, and Drag-Pipes are a catastrophy! You can add an oil filter, and the one Jerry Greer's sells was developed by Geoff Ringley, and it is wonderful. I use them, but you need to get a "cheap" oil filter with less restriction, because the 50Wt oil when it is cold has a hard time moving through the filter with the low return line pressure. I get NAPA's cheap filter. It is for a Lexus 300, if I remember correctly.

Motor Spec Sheets

Parts List, Prices, and Total Costs

Picture Gallery below, during the Build

So, what do you think?

James R. Mosher
(505) 466-7870