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. some 1987/88 B and G-body passenger cars with 305s (or 9C1 Caprices with 350s) with the EST (electronic spark timing) small cap/external coil distributor associated with TBI (throttle body injection) induction) used the ECM and had no mechanical advance provisions (these distributors have a 7 pin module), although early computer-controlled HEI distributors retained vacuum advance in some cases. It is hard on the secondary ignition components in general and just isn't needed in the vast majority of cases. Use dielectric grease on both sides of the rubber insulator. The drawing on the left shows an overexposed transition slot. Customer service hours: 9.30AM – 10PM, Daily Technician service hours: Mon-Sat, 9.30AM-10PM (Last job 8PM) Telephone: 9067 4867 Price: From $250/unit for ChemJET service Aircon Astiquer website Ignition Coil Problems Ignition coils may be the cause of problems, or problems may be caused by failing spark plug wires. This is adjusted by changing the centrifugal advance weights and/or springs to tailor the rate. The button has to be assembled into the cap first, then the rubber insulator. If you are in the 45-55 degree range (about 50 degrees is fine in most cases) of advance including 10-12 degrees from the vacuum advance, you’re in the ballpark. Depending on the cam specs, adding initial timing in addition to or instead of tipping the secondary throttle blades open more may give the best results. Note: Portions of this page appears to have been cut/pasted from a thread located at 72chevytrucks.com. Removal and replacement of the gear is covered in the link, Description of an HEI rebuild. To make sure it is not the hot wire, run a temporary jumper wire directly from the positive side of the battery to the distributor. We'll send you the most interesting Chevy Hardcore articles, news, car features, and videos every week. the pigtail from the distributor is attached to the three terminals closest to the coil (arrow). This in turn causes the cap to fill with ionized air, and this can cause erosion/degradation to the components along with spark scatter and/or voltage bypassing to the distributor advance mechanism, shaft, etc. P0741: TCC System Improper Mechanical Performance. There's a fairly wide tolerance, but it should not be infinite and it should not vary as the wires are flexed and moved around to simulate it in use. The difference is the MSD part doesn't "preload" the vacuum advance can like the Crane limiter plate. To run the engine efficiently without the ECM, sensors, and related equipment fully functional, the distributor and carb need to be replaced at the least. Holley’s Terminator Stealth EFI systems have the same great … What vehicles came stock with a non-computer controlled HEI? insulating the hold down clamp and bolt from grounding the distributor to the engine. Comes with instructions and an allen wrench to adjust it. In these cases an aftermarket vacuum advance cam is required. A lightly loaded engine can tolerate more spark advance than a heavily loaded engine, all else being equal. Other than buying an aftermarket performance chip for the ECM (or buying hardware and software to burn/tune a new chip), there is no way to change the advance curve of a computer-controlled HEI distributor. Find part numbers from the Wells parts catalog PDF above. New replacement HEI power and tach hook-up pigtails are available. The NON-computer controlled HEI can be made into a great distributor for a street or street/strip car. Often a stock distributor is set up to rely on the vacuum advance for a large proportion of ignition advance. I refuse to drive a car that only a computer geek can fix. The only external difference is that one has red and white power leads, the other has red and yellow power leads. The module is the electronic controller that takes the place of breaker points. Generally the vacuum advance can be tailored to suit the conditions after the initial and mechanical advance is worked out. The coil cover has the wiring positions marked on it: If converting to an HEI from a points-type distributor, the wire that was used to supply current to the point-type coil will be a resistor wire. Installation is a simple one-wire hookup. So say the mechanical advance at 2000 rpm is 12 degrees. This is a generic setting for a performance vehicle, and that usually means a rear gear ratio of at least 3.73:1 and w/o OD. On a Chevy V8, the vacuum advance can should be pointing roughly at the passenger side front tire. Build your own custom newsletter with the content you love from Chevy Hardcore, directly to your inbox, absolutely FREE! However, the scope of this article at this juncture doesn't include a full run-down of modified computer-controlled or aftermarket HEI distributors, but is instead primarily aimed at reworking a stock-type HEI for performance duty. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles. Put the probes between the Ground terminal of the coil and the carbon pickup inside the distributor cap. Wells catalog to be used for looking up representative part numbers to find specs for testing. As long as the shaft has up and down movement, you may proceed with the rest of the distributor installation: If there is no up and down movement in the shaft, nylon distributor shims (shown above) need to be added until there is 0.030"-0.060" play. To check the secondary resistance, remove the screws that hold the coil in the cap, remove the coil and touch the negative meter lead to the ring terminal on the black wire (between the red and yellow) and touch the positive lead to the bottom of the coil where the rotor bushing makes contact. The centrifugal advance is used to advance engine ignition timing relative to an engine’s RPM. That's the maximum amount of advance under light throttle cruise conditions some tuners would want to see, and some recommend using less- somewhere around 46 degrees combined advance would be perfectly acceptable in many cases. The other end of the brace attaches directly to a threaded boss on the engine block, just below where the block deck and head meet. If you have disconnected the 4-wire ECM connector going in the side of the distributor or the wiring between the ECM and the distributor is damaged there will, again, be no advance (and the check engine light will come on). MSD and Crane have limiter plates (shown below) that do the same basic thing. Find part numbers from the Wells parts catalog PDF above. Also, the centrifugal advance plate (that rotates on the main distributor shaft as the centrifugal advance moves it), near the top of the distributor shaft sometimes gets gummed up and "sticky," slowing the advance curve and generally preventing the centrifugal advance assembly from working correctly. Another neat wiring aid is the Accel p/n 170072. 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. Stock advance cans may provide as much as 22°-24° of advance. If looking for an HEI, choose one that has the 4-pin module seen at upper left, above. The first area they suggest you check is to make sure all the wire connections on the cap or solid. Don't try to use a computer controlled HEI unless there is an ECM. To test the resistance of the coil, remove the coil cover so you can see the red and yellow wire. Using an adjustable vacuum advance unit allows the vacuum advance to be adjusted for what vacuum the vacuum advance falls out and tips in. This is done by measuring the amount of play between the distributor gear and the thrust washer. A performance cam having excessive duration/overlap/tight LSA specs could require more initial and less mechanical advance. If a connection is loose, current cannot travel to where it needs to go. This is too much vacuum advance if the centrifugal and initial advance has been recurved the as described here. The engine will run, although will have a miss and will detonate, with the #5 and #7 wires swapped. Set it so the vacuum advance starts to drop out at about the same point that the carb power enrichment circuit (Holley power valve, Edelbrock step up spring, or Q-jet power piston) starts to come in. What has to be avoided is too much timing under load; too much timing under load can cause engine-damaging detonation. These recommendations can be considered to be a safe starting point. dual coil units. Number 1 plug wire should be at the front of the distributor just to the driver’s side of centerline. 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. The module will have four wires going into it (two per side). The statement of having about 50 degrees combined advance (initial, mechanical, and vacuum) at cruise rpm needs some clarification. Wells has information on what the various pick up coils should read for resistance. Plug it back in when the timing has been set. Manifold vacuum is a good indicator of engine load. They are not expensive, however, they require a small special tool to remove the torx screws in the module housing. They will soak with oil and compress more than when dry. Take the measurements with feeler gauges. You want the mechanical advance in as soon as the combination will allow, without causing pinging. But, if the ground from the engine to the battery is making a good connection, ignition spark will be none existent. Also the amount of advance supplied by the mechanical advance was set up for the specific application it was used on, and this is seldom what's needed for a performance application. That also means that a fingernail file is no longer the repair tool for roadside fixes. … Note: See the articles on rebuilding the HEI below. If this is the case, the engine will idle high when out of gear and then the idle speed will drop down once it's put in gear, and the off-idle response will be poor. This will be covering the 4-pin HEI module. Other cams require a mellonized distributor gear. 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. And your plugs can develop carbon deposits within just a few thousand miles. Make sure your 12-volt wire is connected to the spade connector labeled BAT. 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. P0736: Improper Ratio for Reverse Gear. This ground may be a wire or a solid strap, as shown below. In many cases, the mechanical advance has to be modified to shorten the amount of advance it can give. If you try to set your initial timing with the engine idling ABOVE the RPM that the mechanical advance has started to come in, getting a correct reading will be all but impossible. 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. Because of this, the pre computer-controlled type HEI distributor is often used; it is a relatively cheap, stand-alone unit with good to very good performance potential, and has a good track record for durability and reliability. It's fine for a naturally aspirated street engine that uses a 0.035"-0.040" plug gap and has a compression ratio compatible with pump gasoline ( Buenos Aires Real Estate, 54x30 Shower Base And Walls, Skull Thuggery Meaning, What Is California Kush, Tim Hortons Steeped Tea 30 Count, Hisense Tv Channel Setup, Ucsf Global Health Fellowship, Godin Lgxt Review,