S&S 97ci Big Bore Kit Part 1- Tech

As we said earlier, the 97ci Big Bore kit is a brand new product for S&S. A straight drop in kit, S&S wanted to make increasing your engine displacement a quick and easy process, therefore the setup requires no splitting, boring, or machining of the cases. You can simply replace your stock cylinders and pistons for the S&S setup, bolt on your stock heads and experience great results. The 97ci Big Bore kit is available for '99-06 Big Twins, and a 106ci Big Bore kit is available for '07-and-later Big Twins. S&S offers cylinders in either silver or black powdercoat to match the rest of your engine. The cylinders feature a 3.927-inch bore which according to S&S is the largest bore they feel can safely be used in a cylinder with a stock spigot diameter. While stock cylinders can be bored to fit the pistons in this kit, S&S will only offer the setup with its own cylinders because it is not confident that the stock liner and spigot material is strong enough once bored to accommodate these pistons. S&S says its liners are made up of gray iron with a 40,000 psi tensile strenth and is much stronger than the stock liners. They also told us they use gray iron because it has much better heat conductivity than ductile iron. You can use your stock heads with this kit which would yield a 9.7:1 compression ratio. Best of all, by using your stock heads, you can save a lot of cash. At $725 for the Big Bore kit, it makes it a very economical performance upgrade with results you can really feel.

While you can still run your stock heads, S&S does recommend using its new Easy Start Cams to help make starting the bike easier. Large displacement and high compression can really take a toll on your battery and starter. As you hit the starter button (or however you fire up your bike) the internal engine components begin to rotate and as they do the compression begins to build. Depending on the strength of your starter and battery, you may be able to power through and the bike will fire to life, otherwise it can be a slow arrr...arrr...arrr as your engine tries turn over wearing down your battery and causing your starter to heat up and potentially burn up. Most people have seen or heard of compression releases that are mounted into the cylinder heads. S&S' new Easy Start Cams have the compression releases built into them. Whereas some cylinder head compression releases are push button (manual), the compression releases in the Easy Start cams are automatic and operate via centrifugal force.

Here's how it works. Each of the two exhaust cam lobes have a spring-loaded compression release built into the heel of the cam at the point where the valve would normally be fully closed. The raised lobe of the compression release holds the exhaust valve slightly open at cranking speed and in return releases some of the compression allowing the engine to turn over easier.

Once the engine starts up and the rpm increases the compression release lobe is centrifugally retracted and the engine runs normally with full compression and no performance loss. The cams are available in chain and gear-drive for '99-later Big Twins. S&S offers the cams in three grinds to target three different performance segments. The 551 cam is geared towards low end torque for touring, the 585 has proven itself as the peak horsepower cam, and the 583 is a good all around cam. These were the cams Norman went with, which according to S&S should provide good low-end torque and horsepower he'll feel from 1,500-5,000 rpm.

While we've given you a quick overview of some of the key components that are going to be installed to bring Norman's old Softie back to life, bigger, badder, and better, Anaheim-Fullerton tech Drifty, was hard at work tearing the bike down. Follow up next month, where we pick up from this point and get into bumping up this 88 to nearly triple digit displacement and see what kind of performance gains the S&S 97ci Big Bore kit and other components yield.

Source:
Anaheim-Fullerton Harley-Davidson
(714) 871-6563
harleyfullerton.com

S&S Cycle sscycle.com