Section 06 - Timing and Ignition Systems
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Tuning Your Engine – Section 6 Section 06 - Timing and Ignition Systems 6.0 Timing Introduction In this Section, we are concerned about tuning vehicles for both street and strip. Without modern knock sensors and sophisticated computer controls, one has to be more careful in the quest for power and drivability. In Sections 3 and 4 we stressed building an engine that can live with today's fuel. In this Section we will discuss how to ensure that you can maximize what you have built without destroying it. Marking Your Harmonic Balancer Balancers with Pre-set Timing Marks To set timing accurately above 4000 RPM, a new set of You can purchase race-type balancers that have the timing scribe marks will have to be added to the harmonic balancer, marks scribed or etched into them. See Section 3.9; Installing since the normal timing tab stops at 15° BTDC. These marks a Harmonic Balancer, for suggestions. must be made on the balancer below the present mark (clockwise from the front of the car). Timing can then be read using the 0° mark on the tab and the new marks on the balancer, while revving the engine to 4000 RPM momentarily. Scribe the marks clockwise from the present mark on the harmonic balancer as shown in the drawing and per the chart below: OEM balancer (left) versus TCI calibrated balancer (right) Original Ignition Settings and Considerations The following specifications in this section were recommended by Oldsmobile when these vehicles were manufactured. For all out competition, racing and aftermarket applications. Please refer to the specifications found later in this Section. Stock distributors on each of the original high performance W-Machines had mechanical advance curves which paralleled best spark timing, given 100 Octane gasoline. The mechanical advance curves, vacuum advance curves and initial timing settings on all models were selected to give best Diagram showing how to measure on the balancer for proper performance – and included normal carbon build up and they timing marks. Standard balancer shown. assumed street equipment, not headers or modified carburetors. For off-road use, in a vehicle where the amount of idle and low speed operation can be held to a minimum, higher timing settings may be used. The Factory recommended the following: Run 103 or better racing gasoline (leaded or unleaded). Disconnect vacuum advance hose at the distributor and plug the hose to avoid any vacuum leakage. Leave the distributor side of the vacuum connection open. This will preclude too much initial advance from the vacuum system, as well as load detonation, which must be avoided, especially with cast or silicon-based pistons. Be conservative in initial timing. Increase timing in small NOTE: the 330 engine will require a new 0 timing mark to steps, listening for any detonation or pre-ignition. be scribed on the balancer prior to these measurements. See the instructions in Section 3.9. - 107 - Tuning Your Engine – Section 6 Check spark plugs after each setting and a short run Advance beyond 35° should be done in small steps and in under load (mild acceleration). If any signs of pre-ignition conjunction with changes in carburetor jetting, slightly are present, reduce timing immediately. richening the system until ultimate power potential is realized. The timing indicator tab on 1968 and newer cars is marked in 2° increments of: -4°, -2°, 0°, 2°, 4°, 6°, 8°, 10°, 12°. The The production curve method of setting the timing may be top edge if the tab is: 14°-15° BTDC. Thus, you can only set used if the mechanical advance curve is known (check the up to 15° initial advance or see that much advance with a curve on a distributor machine). The following chart lists the standard harmonic balancer. To see engine advance above original high performance production distributors with 15, you must install an aftermarket unit as shown in Section standard settings, as well as the Factory's suggested 3.9 or mark the balancer as shown above. settings to achieve 35° BTDC above 4000 RPM. The Factory recommended dwell is 30° 2°. The Factory The most important area to watch in changing timing is the recommended spark plug gap for non-HEI is .032". For advance above 4000 RPM (assuming the vacuum advance MSD and HEI ignition systems, the recommended spark is disconnected). For off-road use, timing should be set to plug gap is .045". give no more than 35° advance BTDC above 4000 RPM. Practical Ignition Advance for Unleaded Street Gasoline Nowadays it is not a good practice to use a distributor with a Thus, if you are running vacuum advance it is important to "quicker than stock" curve in it. This is because of or street know what the total vacuum advance is. For example, let's octane and that it is difficult to set initial timing because it is say that your total curve is in by 2800 rpm and you have 28° likely that the counterweights in the mechanical advance of mechanical advance and 8° of vacuum advance. What you mechanism are already moving due to lighter springs. We would do is rev your engine, with the vacuum advance actually recommend a curve which is "all in at about 2800 disconnected, to 3000-3200 rpm and set your timing at 28°. rpm. Then tighten down the distributor. Hook up the vacuum If your distributor is curved as suggested and you have an advance and you will now have 36° total timing, including the adjustable vacuum advance unit, you should start with a low vacuum advance. This is a good safe starting point. You can initial setting of 4-6°BTDC and then go up or down from now advance or retard from that point for best results. there. If you are running no vacuum advance, you can usually With unleaded fuel, 20°-22° of mechanical advance, plus 6°- start with a setting of about 8-10. What you are looking for is 10° of initial advance and little or no vacuum advance is a between 35-35 at about 3200. good starting point. You want to stay under 37. - 108 - Tuning Your Engine – Section 6 6.1 Ignition System Upgrades Modifying Your Distributor Check for Wear. Older distributors are a mechanical piece, a Unilite conversion for GM distributors. Accel sells both just like the rest of your engine, and are subject to wear and dual point and electronic conversion kits for conventional even damage from misuse. It is highly recommended that GM distributors plus replacement ultra-high quality for vehicles with more than 25 thousand miles, you replace replacement units. your distributor with a reconditioned unit, at the least, or best, rebuild it with new bushings and a hardened shaft with HEI Upgrades. HEI units can be easily upgraded to give a new cam gear (bronze), or replace it with a billet unit. excellent performance, assuming the distributor itself is not worn out, with sloppy play in it. Mallory and Accel sell If you can wiggle the shaft up and down appreciably or conversion kits and upgrade parts for these distributors. back and forth in the housing, it needs replacement because that play will make your engine timing erratic. Upgrading Your Ignition System with New Equipment Upgrading Parts – Standard Distributor. Both Accel and Mallory sell high performance points and condensers for If possible, you should upgrade your ignition system to the standard GM-era distributors. To insure against point either a breakerless system or a "billet" distributor which bounce with high RPM usage, double springing of the are made with much closer tolerances that will keep timing production point springs may be done. The best method is more accurate. We recommend either Accel or Mallory to use Accel No. 110129 points or Mallory No. 102X Series Units. Heavy Duty points. These points are good to 7000+ rpm Mallory offers complete setups for both street and track. without floating. The Mallory Unilite breakerless systems, Magnetic A heavy duty cap and rotor are easy upgrades, and one Breakerless Systems, Dual Point distributors, and HEI Billet would be surprised by the amount of horsepower that can Distributors; many of which are 50-state legal. They offer be gained with this change. Caps, rotors, points and conversion kits and replacement parts as well. Please see condensers wear out rather quickly, especially where the chart that follows and contact Mallory at higher cylinder pressures and increased engine load are www.malloryracing.com or call 216-688-8300. present, as in a modified or performance engine. If you are Accel also offers performance replacement distributors for using a standard GM distributor and want great both standard and HEI systems that are 50-state legal. performance, you will find that changing these components They also sell billet replacement electronic breakerless at every other oil change is a good idea. systems and high performance electronic breakerless Going Electronic. Mallory and Accel sell conversion kits to distributors. Please see the chart that follows and contact make the system breakerless. This will ensure constant Accel at www.accel–ignition.com or call 216-69-88-8300. signal and no timing inaccuracies, as well as allow much MSD ignition systems offer a host of ignition boosting higher voltage. To the plugs. Mallory's E-Spark Conversion systems, including high performance coils. Many of these Kit will convert their own point-type systems, and they have components will work with either brand of distributor. - 109 - Tuning Your Engine – Section 6 6.2 Spark Plug Science and Spark Plug Wires Spark Plugs and Plug Heat Range A hot plug has a slow rate of heat transfer; therefore it runs the R43 best for 10.0:1 and higher CR and the 44 for hotter and prevents fouling.