The V-Twin Motorcycle Performance Guide is your source of information to build, tune and maintain high performance Harley-Davidson street and racing motorcycles. You will find the information needed for tuning, modification, preparation and maintenance for your Harley-Davidson motorcycle engine. Whether you are a new rider looking for  step-by-step instructions to modify a CV carburetor, installing a new cam, want to find out what impact drag pipes have on horse power and torque of your Harley-Davidson engine, or an experienced drag racer looking for the latest cam specifications, the V-Twin Motorcycle Performance Guide has the technical information you can use.

For interests ranging from motorcycle drag racing, hot street performance or just getting the best possible performance from your current bike, V-Twin Motorcycle Performance Guide provides a reference guide and forum for your interests. This is a source of solid technical information that you can put to use today. When it comes to engine tuning, changing carburetors, carburetor re-jetting, picking a camshaft, camshaft installation, dyno tuning, exhaust systems, cylinder head modifications, performance modifications, suspension tuning or just routine maintenance, V-Twin Motorcycle Performance Guide has the answers you need.

Information provided in the V-Twin Motorcycle Performance Guide covers engines made by Harley-Davidson and its clones. We have included information on  the 1340 Evolution engine, Twin Cam 88, Twin Cam 95, Shovelhead 74, Shovelhead 80, Sportster Evolution, Sportster Ironhead, Sportster XR, and Buell. If you can't find the engine you have listed here, its to valuable as a museum piece to modify the engine.

  • Looking for the easy way to increase the horsepower of your big twin motorcycle? Making Power is your step-by-step guide to improve your horsepower and torque. We have assembled three different Evolution engine performance packages that can be put together in a weekend.
    Build a 64 horsepower Stage 1 bike
    Build a 74 horsepower Stage 2 bike
    Build a 82 horsepower Stage 3 bike
    Build a 95 horsepower Stage 3 bike
    The Horsepower Gallery provides a quick list of horsepower obtained by many engine combinations. The horsepower, engine type, cylinder heads, carburetor, camshaft and frame type are all listed for reference.
    The Drag Strip Gallery showcases some of the quickest V-Twin Racers around. Compare your times to these racers, or better yet send your results to us.
    The Land Speed Racing Gallery is the ultimate challenge. Just how fast will a V-Twin engine run. If you thing your bike is fast, see what can really be done.

  • The Performance Shop Manual is a performance and technical reference manual for engine modifications. This is where you will find all the motorcycle modification information. There is a lot of serious v-twin performance information available for your review. 

  • The Shop Manual Appendix section contains contains information of interest to all high performance motorcycle riders. Here you will find a Shop Manual that provides information on maintenance, tuning, shop data  and troubleshooting your motorcycle. 

  • Ever wonder how the best racers always seem to know how their motorcycle is going to perform? Lots of experience is one way, the other is the use of powerful computer tools that predict performance and tuning information. The selection of motorcycle and automotive Performance Calculators provide ways to:

Estimate your engine horsepower
Estimate your top speed and how modifications will change it
Estimate your 1/4 mile time and how modifications will change it
Estimate your 1/8 mile time and how modifications will change it
Determine the best exhaust pipe length
Compute air density
Compute overall gear ratios
Compute cubic inches displacement for an engine

  • The Links provide a list of manufacturers of high performance motorcycle parts and accessories. Most of the premier providers of Harley-Davidson performance equipment are listed here.

  • Search allows you to do a keyword search of the V-Twin Performance Guide site. Enter the information you are looking for, and it will find the pages to visit.

  • The Miscellaneous section to V-Twin Performance provides the V-Twin Café with an outlet for new, serious or whimsical information. You never know what you may find there.

  • The Books and Manuals section gives you the names of essential items for your high performance reference. You can order these performance books and manuals for your Harley-Davidson thru the Motorcycle Performance Guide by special arrangement from Barnes and Nobles. A wide variety of motorcycle books are available online from Barnes and Noble.