hei coil problems

She gets 23 MPG highway, and has no electronic parts except for the chip in the HEI ignition. On almost any carb, there are vacuum ports that provide manifold and ported vacuum. Steel cams require a bronze or plastic composite gear. All rights reserved. Crane has an adjustable vacuum advance can kit, p/n 99600-1. If there is no EGR being used, the amount of vacuum advance needed will be around 10-12 degrees. You will need to remove it and take it to an auto parts store that has a module tester. But it does have its limitations and it has a few built-in design flaws- or "compromises"- like most any mass-produced part that has a limit on how much cost the manufacturer can justify. For a stock or RV-type camshaft, 8 to 12 degrees initial is a good starting point. Sometimes, heat can cause these to not work properly, so it is recommended to have them test the module 3 – 5 times as the module may not show to be bad until it develops some heat. This is located inside the distributor, and has the green and white wires from the pick up attached on one end, and a terminal block on the other. Total timing is not affected as much by the cam timing; that's more a function of the compression ratio, fuel octane, quench, engine temperature, air/fuel mixture, cylinder head design and material, etc. If the voltage drops below 10.5, check your battery. By using ported vacuum and an adjustable vacuum advance can, you can give the engine extra timing under light throttle cruise conditions. This is not needed or wanted for the HEI- it needs to be supplied with full system voltage without any resistor wire or ballast in the circuit for best performance. The HEI distributor is widely available from the aftermarket. Generally the vacuum advance can be tailored to suit the conditions after the initial and mechanical advance is worked out. This wire should be part of your original wiring or can be purchased separately. Swap springs until you get it close to these specs. In addition to the interrupter switch, a starter brace should be used to help prevent broken starter noses or damage to the mounting ear of the block. I drive a ’78 Oldsmobile Delta 88 Royale. An adjustable vacuum advance can lets the tip-in point be tailored to the engine vacuum, so the vacuum advance will start and stop at the right amount of vacuum. The large diameter of the cap helps to prevent this and it works well enough in a passenger car, even with the wider gaps that were used for some applications. insulating the hold down clamp and bolt from grounding the distributor to the engine. This is too much vacuum advance if the centrifugal and initial advance has been recurved the as described here. The initial, centrifugal and vacuum advance work together overall but are independent of each other; each adds the appropriate amount of timing advance to supply the correct spark advance to the engine under all RPM/engine load conditions. If an attempt to change the advance curve is made on a distributor that suffers from these problems, the mechanical advance may not work as smoothly as needed. This is done by measuring the amount of play between the distributor gear and the thrust washer. Hold the distributor down against the intake (or block) with one hand and with the other hand lift up on the top plate of the distributor shaft (usually where the mechanical advance mechanism is located) to be sure there is some play and that the shaft isn't "solid"- which would indicate the distributor was bottomed out and there was no clearance. Preloading the vacuum advance changes the tip-in point and also requires the initial timing to be readjusted each time the vacuum advance limiter plate is adjusted. If, for some reason you have no spark coming from your distributor, the following will help you check and test the installation, connections, and components, of the unit so that you can get your engine running. Number 1 plug wire should be at the front of the distributor just to the driver’s side of centerline. If you have been hesitant on switching to EFI because you like the traditional look of a carburetor? The first thing to do is set the initial advance correctly- that often means an initial advance of between 12 and 24 degrees (depending on mainly the camshaft), with the remainder coming from the mechanical advance. Small HEI Distributor with Externally Mounted Coil or; Large cap (internal coil) distributor. In many cases, the mechanical advance has to be modified to shorten the amount of advance it can give. Newer HEI distributors (1981-86 for passenger cars exc. Put the probes between the Ground terminal of the coil and the carbon pickup inside the distributor cap. If the blades are opened too far, the idle quality and off idle response will not be good. If that isn't possible, another way is to replace the module with a known good module. A gasket can be used under the shims. This can cause the vacuum advance to add advance when it's not wanted. This is not a bad thing, it leaves funds available for parts that WILL make the car faster! Wells has information on what the various pick up coils should read for resistance. If that's not your #1 plug wire, or your vacuum can is pointed in another direction, the distributor may be installed one or more teeth off. The correct gear material/treatment has to match the type of camshaft being used. It is hard on the secondary ignition components in general and just isn't needed in the vast majority of cases. Note: See link HEI vacuum advance specs, below. The only external difference is that one has red and white power leads, the other has red and yellow power leads. They are not expensive, however, they require a small special tool to remove the torx screws in the module housing. Ignition Coil Problems Ignition coils may be the cause of problems, or problems may be caused by failing spark plug wires. This condition will cause a stinky "rich smelling" exhaust (it actually is unburned hydrocarbons, not necessarily too rich). Note: Portions of this page appears to have been cut/pasted from a thread located at 72chevytrucks.com. In many cases the vacuum advance should use a full manifold vacuum source on the carb- but this is not written in stone. Cheap/offshore buttons can have excessive resistance; this causes heat and can in extreme cases melt the surrounding plastic of the cap and the engine will quit. It’s a combination HEI battery/tach pigtail that has a connector for both power to the HEI and the connection for the tach, molded together. More on how ported may be preferable to manifold vacuum is here, by noted carb tuner, Cliff Ruggles. Use caps and rotors that have brass terminals. Along with that, there's often a need to limit how much vacuum advance is supplied. Stock advance cans may provide as much as 22°-24° of advance. So fix it first or get another HEI to start improvements on; just make sure you are getting the right one for your engine- they were used on ALL makes of GM inline and V6/V8 engines and all look similar. Failure to do this can lead to an early failure of the module. It's simple, easy to tune, and plenty powerful to light off any naturally aspirated engine up to 7000 RPM if properly equipped. Plug it back in when the timing has been set. Disconnect the green and white wires from the module and touch the positive meter lead to the green wire and the negative lead to the white wire. Make sure your 12-volt wire is connected to the spade connector labeled BAT. Also, you may find that the engine is cooler running around town in traffic and has much better throttle response. A typical advance curve for an engine built with a mild camshaft and having a compression ratio correctly matched to the cam will look something like this: The above gives 46-48 degrees of advance (including vacuum advance) under light throttle cruse/high vacuum conditions. If the distributor fires using the jumper wire, run a new hot wire from your switched 12-volt source to the distributor. Be aware that if the carb or induction system is overly restrictive there may be vacuum developed at wide open throttle. © 2020 Power Automedia. You want to end up with ~0.020" (no less than 0.015") on a Chevy distributor; some engines like the Olds need to have the end play adjusted differently. On a Pontiac V8, the oil galley plug adjacent to the distributor gear can be carefully drilled with a small numbered bit to direct pressurized oil to the gears. A relay that delays the ignition from being energized- giving the starter time to get the engine turning over- can be wired into the ignition feed wire. Performance cams will require more initial advance, all the way up to the point where- in extreme cases- the ignition advance is locked in at the total advance amount and there's no curve. Use these springs to give you an advance curve that starts at about 800 RPM and ends at 2800-3200 RPM. When checking for 12 volts, do so while you are cranking the engine. In order to fix your car's problem, you must first know how to troubleshoot in order to determine what exactly the problem is. Put the switch in series with the power wire and route the wires inside the vehicle so the switch is within easy reach of the driver. The engine will run, although will have a miss and will detonate, with the #5 and #7 wires swapped. Many times, a low-voltage issue can cause a myriad of problems. If the meter jumps around as the wires are flexed, or if the resistance is drastically higher or lower than 600Ω-1000Ω (or is infinite), or if there is a reading between either wire and the metal case of the pick-up coil, it's bad. This will be covering the 4-pin HEI module. Some part numbers for a stock-type "990" series module: Use a heat sink paste (available from Radio Shack and computer shops) on the bottom of the module and be sure the surface of the distributor body where it mounts is clean.

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