Speed And Science Ltd.

Performance parts for Harley-Davidson (TM) Cycles

Speed And Science – Frequently Asked Questions:

*Need more info? Please use the form below.

Harley-Davidson engines are awesome for many reasons, but they just beg for more power! Over the years many attempts have been made to improve this area, but most of them require a lot of trial-and-error, customization, adaptation, etc. We’ve tackled the very root of the problem – the heads. Thanks to our engineering and manufacturing expertise we were able to apply the latest in the internal combustion technology, and the results speak for themselves – just replacing the heads alone wakes the engine up dramatically! Adding a performance-oriented fuel/exhaust system and camshaft will further improve the performance. But we didn’t stop there! We have also addressed many inherited problems in order to significantly improve performance and reliability while remaining bolt-on to OEM components. All that to help you enjoy the ride, mile after mile, season after season.

The intake port interfaces on our heads have been designed to accept both Individual or Y-split manifolds. That feature allows you to use either (dual or single) system on the same headset! Each system provides unique advantages and it’s up to the builder to select the right combination. We’re here to help, too.

An experienced builder should be able to cross the 1HP / 1CUI ratio quite easily. As far as variances between sets, rest assured they’re all identical and true to the original design down to microns! All of our parts come right off of our multi-axis machine tools completely finished and ready to use, without any need for traditional hand-finishing methods. We are committed to make all of our parts as perfect as possible.

We (or any other respectable manufacturer) don’t sell our headsets based solely on the flow numbers.

Exorbitant CFM numbers have been an imperative back in the day, but so was an asbestos! For years now, every automotive engineer/tuner is very well aware that “…engines run on velocity, not CFM” (Joe Mondello). E.g. 300CFM port on a 96CUI engine that needs only 167CFM @ 6,000RPM will most likely decrease performance. Instead, a port designed for correct velocity/efficiency will make the max. power where it matters the most. At this point the math gets complicated real quick, so here at Speed And Science we’ve optimized the ports for real life performance. Bottom line? Our heads offer fantastic upgrade for both your riding style AND your bike, year after year.

While 5-angle seat geometry reduces some flow restrictions, it is far from optimal. We never settle for anything less than perfect! Since we have the best technology available, we use specially profiled cutter for the smoothest blend possible. No extra cost!

We’ve developed the combustion chamber geometry that promotes super-fast flamefront, no dual plug needed.

For example, for best performance we routinely set the ignition timing on our Shovelhead test engines @ 24-26deg. BTDC, instead of factory 35deg.

You should be able to re-use most (if not all) of your existing peripherals. For example, our Shovelhead exhaust ports accept both OEM single bolt mounts and aftermarket three-bolt flanges. Shovelhead headset comes standard with the intake manifold, make sure to select the correct one for your favorite carb[s].

For our EVOLUTION headsets we strongly recommend purchasing our matching intake manifold (S&S and KEIHIN interface available). 

For detailed instruction please refer to the Installation Manuals, available to download here, and of course we’ll be happy to answer any other questions via the form below.

Our intakes are proprietary and have been designed in conjunction with our (also proprietary) heads. Such arrangement provides an uninterrupted flow and removes any chances of an air leak. As such our manifolds do not fit OEM heads.

The heads have been designed for a high-octane pump gas. North American 94 Octane works very well once the engine has been tuned properly. Non-Ethanol fuel is preferred if available.

Our heads require specific (OEM in most cases) pistons in order to take full advantage of  the squish bands. Please refer to the Installation Manuals for more detailed info.

In order to generate an intense internal turbulence and promote super-fast flamefront (gain extra power), certain areas of the combustion chamber match very closely the piston’s dome shape. When building an engine, the gap distance between those two should be set to .025″ – .035″ at TDC (both cylinders).

Acquiring custom-made replacement hardware can be very aggravating, expensive and time-consuming. Hence, we’ve designed our heads around OEM hardware, including the entire valvetrain. R&R procedure for any component (e.g. valve guides, seats, etc.)  is exactly as per factory manuals, thus making future service (if need be) very easy.

The 6061-T6 aluminum used in our billet products has a tensile strength of 60,000-70,000 psi. Our cylinders provide generous wall and base thickness, also the critical areas have been designed with stress-reduction features in mind.

Our aluminum Shovelhead cylinders are 9lb lighter than the cast iron parts.

Yes, due to the increased fin area the heads run up to 35F cooler vs. stock. Cylinders run about 50F cooler compared to the cast iron also.

We supply the heads fully loaded up, no exceptions.

Our products are being sold exclusively via our Website.