CMS A-Series Fast Road Camshaft – BMC 731 Profile Equivalent
Precision In-House Engineering for the BMC A-Series Engine
Upgrade your classic Mini to a period-correct, sporting specification with our precision-machined A-Series camshaft, engineered exactly to the historic BMC 731 profile specifications.
Originally developed by the British Motor Corporation's Special Tuning department, the 731 profile is a legendary choice for spirited road driving and classic road-rally events. It is designed to give a massive mid-range power boost to standard or mildly tuned A-Series engines, providing a strong, usable power band from 2,000 to 6,000 RPM. This profile is highly favored because it delivers a noticeable crispness to the throttle while still maintaining a perfectly acceptable, smooth road idle.
Technical Specifications:
- Application: Period-Correct Fast Road / Classic Road Rally
- Power Band: 2000–6000 RPM
- Cam Lift: 6.35mm (0.250") Inlet / 6.63mm (0.261") Exhaust
- Valve Lift: 7.92mm Inlet / 8.28mm Exhaust (with standard 1.25:1 rockers)
- Valve Clearance (VC): 0.30mm (0.012") Inlet / Exhaust
The CMS Core Exchange Service
This profile is precision-ground onto an original, inspected factory A-Series core. To purchase this camshaft, you can either:
First Option: Ship your original, clean A-Series camshaft to our workshop. Once it passes our strict structural integrity and gear wear inspection, we will dispatch your new CMS performance cam.
Second Option: Pay an upfront core surcharge at checkout. We will ship your CMS camshaft immediately, and refund the deposit in full once your usable exchange core arrives at our shop and passes inspection.Installation & Break-In Requirements
To ensure the longevity of your flat-tappet A-Series valvetrain, CMS requires the following installation steps. Failure to follow these steps will void the product warranty:
Mandatory New Followers: Never install a new or reground camshaft with used lifters. You must use brand-new, high-quality flat-tappet followers.
Check Valvetrain Geometry: Because this is a high-velocity regrind with a slightly reduced base circle, you must check rocker arm geometry. Ensure adjustment screws have proper thread engagement. Rocker pedestal shims may be required to restore a perfect 90-degree alignment.
Break-In Procedure: Coat all lobes and follower faces heavily with high-zinc ZDDP assembly paste. Upon initial startup, do not idle the engine. Run the engine immediately at 2000 to 2500 RPM for 20 minutes to work-harden the new lobe surfaces.Trademark Disclaimer
Classic Machine Shop CMS is an independent manufacturer of precision-ground engine components. Any reference to original manufacturer names, profile designations, or original part numbers is strictly for informational and comparative purposes to describe the physical geometric dimensions of the lobe profile. Classic Machine Shop has no official affiliation with these trademark holders.
