Mallory Ignition Mallory CT Pro Ignition Products 6800m - Manual (Page 3)

Maximizing RPM limit
There are several engine component or assembly related items that can contribute to the CT Pro Ignition’s
rev limiting circuit activating below the pre-programmed limit of 8,800 RPM. Previously, early rev
limiting issues were not necessarily addressed since most people simply set the rev limiter to a higher rpm
setting. In order to maximize the rev limit of the CT Pro Ignition system, special attention should be paid to
the following engine component or assembly related items.
Distributors-
Cause Excessive end-play causes cylinder to cylinder timing to vary.
Cure Reduce endplay to a minimum, but still allowing for housing expansion. This varies depending
on the length of the housing and its material.
Cause Excessive clearance between the camshaft’s drive gear and the distributor’s driven gear.
Cure Use an oversize gear to reduce the backlash to a minimum. Also, starting with a gear with an
undersize inside diameter and honing it to precisely fit the distributor shaft also will help.
Cause Cylinder to Cylinder timing variation
Cure The greater the variation of the timing from cylinder to cylinder is, the earlier the rev limiting
will occur. The rev limiting function is based on the shortest time between two cylinder firings.
Cause Distributor triggering variations
Cure Different distributors use different internal triggering styles. The more accurate and stable the
trigger signal is, the more accurate the rev limiting will occur.
Camshafts-
Cause Cam Walk
Cure Roller camshafts especially need to have cam walk kept to a minimum. Depending on the design
of the drive being used, this can be controlled by a cam button or thrust plate. Typically, endplay
or walk of .003” to .006” is considered acceptable. While the lobes on a flat tappet camshaft are
tapered, endplay can still be an issue.
Cause Uneven Camshaft Rotation
Cure Minimize the slack or slop in the cam drive whether it is a chain or belt style. The smoother the
camshaft rotates, the less variation in the distributor rotation speed.
While there can be other causes, optimizing the above items, in addition to the general condition of engine
components, can definitely affect an engine’s performance. You may also find some variance based on the
type of testing being performed. You can expect some difference between engine dyno, chassis dyno, and
on-track test results.