Based some 50 miles north of downtown Chicago, Indian Motorcycle of Libertyville, Illinois, is an authorized Indian Motorcycle dealership with a story to tell.
It all started with trying to eke out that illusive extra few horsepower from the respected, reliable, but perhaps limited Indian Thunder Stroke 111” V-twin as used in stock Big Twins.
Managing Partner/Owner Don O’Shea explains: “Don’t get me wrong, it is a great engine for what it is, but there is more performance hidden away in there, and we set about trying to find it.
“We tried all the conventional approaches, as have most other Indian dealers - we got into tuning and explored all the low hanging fruit such as slip-ons, intakes/air cleaners, and the new cams when Indian released them, but we still weren’t seeing the kind of improvements we were sure we could get - the kind of improvements that would excite and motivate customers.”
Don’s business partner, Todd Gaines, has two and four-wheel experience and takes up the story. “It’s interesting, it seems that with the Scout engine Indian had options it could exploit from the word get-go, and that is a good performance engine that can be massaged.
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| The newly cast cylinder head has a redesigned chamber and intake port for larger springs and valves |
“The 111” Thunder Stroke isn’t a bad engine, not at all, it just appears not to be performance- optimized. It is as if the primary concern was emissions compliance - that and wanting to be as faithful as possible to the iconic 1946/48 era engine’s looks. The way the exhaust has to come out of the cylinder heads for example constrains the design of the head.
“So, our next step was to start working on the heads, but we quickly found that it was going to take more than just porting and larger valves, and any of the other things you would normally look to do to a head. It required some reconstruction.”
The result has been the establishment of a new company called IPS (Indian Performance Solutions) and the complete re-design of an entirely new, repeatable, newly cast cylinder head for the Thunder Stroke 111.
“We redesigned the combustion chamber as well as the intake port with some really good results, but doing so is so labor-intensive and time-consuming that we decided to make the investment and get our design cast, so we would have a repeatable product that we could pull off the shelf and bolt on.
“In every way, shape and form it resembles Indian’s stock 111 head, except for the two key factors of combustion chamber and intake port redesign. We’ve also upgraded the valve springs and are using a cam of our own design.
“Overall, we are reliably getting around a 40 hp increase, with a little bit of variation. The stock 111 is 73 hp/103 ft lbs of torque at the rear wheel, so we are getting around 112 hp and around 125 ft lbs torque, which rolls in at the bottom end with peak torque at around 3,800 rpm.
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| The contour of the back side of the exhaust valve is different to the one the factory uses |
“People fixate on horsepower, but torque is where it’s at; the cam selection puts us in the middle with good numbers on the top without giving up too much on the bottom.”
The upgraded springs and valves come with the heads and are very similar to Chevrolet LS valve springs. The heads are cast on the west coast and machined in Reno. Through Indian Performance Solutions (IPS), which is headquartered near its dealership at Libertyville, Illinois, Don and Todd have relationships with the key suppliers needed for the production and tuning of its new cylinder heads and did the prototype, pilot testing and durability testing there, and worked closely with its suppliers to get the drawings and manufacturing specs drawn up on a supply side management basis, with IPS owning the intellectual property on the designs.
Don continues: “When we redesigned the combustion chamber, the objective was to raise the compression ratio - from 9.5-1 stock to 10.5-1 for our heads with the existing pistons and rings. We also upgraded the exhaust valve - the contour of the back side of the valve is different to the one the factory uses.”
Don says that the plan is, ultimately, to make the package available as a retail kit, with a tuner and map for bolt-on and re-flash install. Initially Don says IPS will focus on sales to other authorized Indian Motorcycle dealerships.
“As a cylinder head package rather than complete top-end kit, it will have a price advantage over some of the other Thunder Stroke 111 performance solutions that are being talked about, but with largely similar horsepower and torque gain results.”
INDIAN MOTORCYCLE OF LIBERTYVILLE
www.indianmotorcycleoflibertyville.com
