Ignition

Distributor Rebuilding

Author : Robert Sarama

Complete TR6 Distributor Restoration and Repair – all units disassembled and meticulously cleaned. Housings glass bead blasted and polished. Oilight bushing(s) individually turned and replaced. Shaft and action plate assembly aligned and balanced. Springs, seals, screws and tack lead replaced. Vacuum unit(s) tested and repaired. All units dynamically tested on a Sun Distributor tester and brought back to OEM specifications. Performance curve modifications, dynamic performance testing and powder coating available. Two to three week turnaround. References and photo examples upon request. Send email for a quote. Bob Sarama lucasdistributors@yahoo.com

Dolomite Sprint Advance Curve

Author : Garth Newton

An Excel sheet showing a couple of advance curves for a Sprint.
Plot points can be changed to update the graph.

programmable ignition 2.0

Dolomite Sprint Ignition System

Author : Mark Larmour (SPRINTPARTS)

The standard distributor fitted to a Dolomite Sprint has a conventional Kettering ignition system. The spark energy available from a conventional ignition system falls off with increasing engine speed; ie, the more sparks required, the less energy per spark. This is because it takes an appreciable time for the coil primary current to build up to its full value. As engine revs go up, there is less time available for the current to build.

One method of improving “your spark”, is to fit High Energy Ignition. HEI is commonly used in modern cars due its ability to burn lean fuel/air mixtures to meet pollution standards, which is achieved with longer and larger sparks. HEI is so called because it provides maximum energy storage in the ignition coil by extending the dwell, meaning that coil current can flow for most of the time instead of only when the points are closed. Dwell extension means that high voltage is maintained even at high RPM because the switching transistor is off for a fixed time, giving fixed spark duration at any RPM. This longer and larger spark assists with combustion giving maximum burn for fuel/air improving power and economy. HEI assist motors that were once reliant on high-grade Super petrol, to run on the lower grade LRP and unleaded fuel now available. Even the most basic HEI is guaranteed to improve any standard or even modified ignition system.

Distributor regraphing is a tedious and sometimes black art. If the distributor shaft, bush, and/or base plate is worn or the advance springs stretched or soft, the ignition timing will not be what it should. Although static and idle speed timing may be correct, the advance curve to full advance may be erratic or more than likely too fast, creating ignition pinging. An engine running too much advance risks the possibility of detonation damage, melted pistons, blown head gaskets, whilst an engine with insufficient ignition advance lacks performance and can have excessive fuel consumption.

Probably the most cost-effective method to produce more accurate ignition timing, is to install a Programmable Ignition timing unit in conjunction with the low cost HEI. These units are programmed via a keypad to a programmable chip, setting ignition advance for start, mid and max RPM, in a 2 stage advance curve. A second curve can be preprogrammed which can be selected with the engine running giving more or less advance, which is ideal in hot weather or to accommodate for a change in fuel quality. The PIT will also act as a rev limiter, and anti-theft unit. The distributor must have the mechanical advance unit locked and the ignition advance is then achieved by electronically advancing or retarding the input to the HEI via the programmed silicon chip.

Personal experience over several years of mainly Sydney driving with a HEI and PIT using a standard points installation distributor in a Dolomite Sprint has seen a marked improvement in fuel economy of approximately 10%, and much improved mid range RPM torque.

Tuning the Lucas Distributor

Author : Marcel Chichak (chichm@telusplanet.net)

This document will look at tuning the advance curve of Lucas distributors, 23D/25D and 43D/45D types in particular, but the principles and approaches used apply to any distributor with mechanical advance. The effect of changing spring rates and free lengths will be analyzed, design charts and examples will be presented.

lucas distributor tuning

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