Feature Article: The GM HEI System Explained!

In a squarebore, the bores are closer to the same size, though, in some squarebore carbs, like cfm Holleys, the primaries may be noticeably smaller than the secondaries. However, even then the bores share the same centerline. Many aftermarket intakes, such as mine, and the Edelbrock Performer and RPM, etc, are “dual pattern” intakes the area where the carb bolts on looks like a butterfly. Either a squarebore OR spreadbore can be physically be mounted on them with no adaptors. Carter Thermoquads, Rochester Quadrajets, and Holley ‘s, ‘s, and ‘s are spreadbores. If the intakes are true squarebore intakes four individual holes or true spreadbore intakes again, four individual holes, though of different size , you cannot really bolt a squarebore carb on a spreadbore intake and vise versa. In the case of putting the squarebore on the spreadbore intake, the primary bores of a spreadbore, though small, are spread further out than the primaries of a squarebore. The squarebore primaries of the carb would not line up well with the holes in the manifold.

Chevrolet Performance 19333158

They are knowledgeable and friendly. First, you need to decide what type of system you want. There are three different types.

Hook up timing light to #1 cylinder. Chevy performance engines run best with initial timing set at 10 degrees before top dead center. Adjust as necessary by rotating distributor.

Report aztec bf answered 5 years ago The 0 degree mark is just a reference point. When timed you will be advanced from 0. If you use a vacuum gauge along with timing it you will get optimum timing. You should have minimum in. As you adjust timing you will notice vacuum changes time for max vacuum plus or minus only small amounts. Also here is a little ready reference you can use for timing and troubleshooting.

Damaged Mallory HEI – You Break It, You Fix It!

This is a must on any car that will not allow the use of the late style full size HEI distributor. With its OEM appearance, this unit is superior in every way to a point style distributor. Read this complete ad before purchasing this product. Before you ask any questions about this product, please read the “Very Important Note” in the lower section of this ad.

Dec 13,  · If you are lucky, and the engine fires o.k., let the car run for 5 or ten minutes to get the engine warmed up, then shut it off, hook up the timing light, and set to whatever your specs call for, Then hook up the vacuum line to the vacuum advance, and that should be it.

Sometimes they get pinched or broken inside the insulation and you can’t see it. I’ve got an 87 V10 pickup with an 89 motor in it and I’ve got all kinds of little problems with it. Little things like stalling when you go into reverse, stalling at traffic lights, etc. Good luck and post your results! You know, I would stick with the TBI. I’ve got enough bottom end torque to pull tree stumps if I can get the traction!

Post Reply I love my Chevy Chevette!

Ignition Solutions for Garden Pulling Tractors and Older Small Engines

A Tuning Procedure by Nathan Hall So happens that while Nate was writing this procedure, I had the need to use it on my newly rebuilt As an amateur restorer, I first set out to create the engine stand front end of a badly burned out and a portable starting caddy I call The Start Kart. The cart has two battery bays, storage for the compression tester, timing light, misc fittings, etc. Most people put all that on the engine stand, but I wanted it portable so I could roll it up to anything to diagnose problems.

HEI for your Stock Dizzy; PCV for your //; The Chevy // Tuneup Guide. As with all of the content on this website, you can simply click on any picture to get its largest size. Place it back on the distributor, twist it until the clips line up and you feel the cap click into place on the distributor. Don’t clip it on yet.

One minute you can be soft and absorbent over the rocks and trails, the next you can be cranked up to the max for high speed pre-running over the ruts and rocks. As it turns out pre-running can be hard on a stock ignition system. I found this out during a spring trip into the fern covered mountains when some high-speed pre-running fun shook a bug out of the ignition system of my Jeep CJ Several rounds of testing and troubleshooting yielded no cause and no fix for the ailing sparkless stock Ford Duraspark ignition system.

Before spending too much time on it, I decided it was time for an upgrade. They also make them for the 6 cylinder engine as well. They’re a durable 1-piece design with the coil and module mounted internally for an easy 1-wire hook-up. Plus by eliminating the stock AMC ballast resistor, more ignition voltage results and you get improved spark that permits a bigger spark plug gap, resulting in more power and reduced plug fouling.

When you look at a stock Jeep CJ-7 ignition system, it consists of a few key components. First the starter solenoid provides power. You also have a coil, the distributor, a vacuum advance, a cap and rotor, below the cap and rotor, an induction coil and a star gear that tells the ignition module when to ground the coil, which in turn sends spark to the rotor and out to the spark plugs. All of these main components are in different locations under the hood and a bunch of wires run back and forth to interconnect the components.

My Stock Ford Duraspark ignition system had a few minor upgrades.

FiTech EFI Frequently Asked Questions – Ignition Control

From Pontiac powered car. Should be the same Fits non air car. Some minor surface rust. For V8 cars. Has splits on upper bolt holes.

Dec 10,  · I am also trying to hook up a factory tach to a Blazer but it has a 77 engine with an HEI distributor. There are two wires coming off the tach connector, the red one goes to the fuse box and the black one goes thru the firewall and is laying there unconnected.

Installation Instructions A tachometer is a good addition to any vehicle equipped with a manual transmission. Installation of the Autogage Tachometer was fairly simple with only minor wiring including a wire to the distributor, a good ground, a 12 volt switched power source and a wire to power the tach’s light. The following write-up is an overview of the installation I followed and includes a few illustrations from the installation guide provided from Autogage.

To change the tach to operate on 4 or 6 cylinder engines, a pair of dip switches are located within the tach to make the adjustment. To get to the cylinder dip switches you have to remove rear cup by placing the tachometer face down on. A phillips screw retains the cup so remove that screw located on the back. Gently lift the cup off to expose the circuit boards.

Careful not to pull on the wires.


High-flowing heads, fuel delivery, cams, pistons, and compression are the main cast members in this mechanized drama. An under-performing ignition system will drag down the entire show. MSD Ignition has built an entire industry around providing support to the other characters in the internal combustion epic, and the introduction of the MSD Ready to Run is sure to bring the HEI crowd to their feet.

In , Delco, a division of General Motors, announced a new ignition system that eliminated contact points and condensers.

Adjustable shocks are a great thing. One minute you can be soft and absorbent over the rocks and trails, the next you can be cranked up to the max for high speed pre-running over the ruts and rocks.

Knee deep in hookers and gin Is it a big cap HEI distributor? If so, the one wire or just a empty spade connector coming from the terminal marked btty goes to ignition hot. I believe that to be black with a yellow stripe near the factory coil location on the right inner fender. The terminal next to it marked “tach” goes to a tachometer if you want to hook one up. The 3 wire connector that goes from the cap to the distributor is the wires from the pick up and module to the coil.

If it is a small cap with one wire coming out of the distributor it is a points distributor and should be thrown in the bushes and replaced with an HEI. That one wire goes to the negative side of the coil with ignition switched battery voltage to the positive side of the coil. Really HEI is cheap and simple and works loads better than crappy old points. It sounds to me like this is what you’re seeing.

If it is a small cap with two weatherpak connectors, one four wire, one two you have a computer controlled fuel injection distributor that requires a computer to advance the timing. The two wire connector goes to the coil, the four wire to the ECM.

Timing Is Everything

In addition, here are a few things to note: Some later models used a 5-pin module for a knock sensor Computer controlled engines used a 7-pin module When replacing a points distributor, you should use a distributor with the 4-pin module. You could also use a distributor with a 5-pin module and replace the module with a 4-pin one. That would require plugging the extra hole in the housing where the connector for the knock sensor wiring used to be.

Distributors using 7-pin modules can not be converted to non-computer controlled use since they do not have advance mechanisms they use the computer to control the advance. Also note that different GM divisions used distributors with different shafts and gears.

The GM HEI distributor’s springs can be replaced with three different weights of springs that, in effect, allow the advance at lower rpm. The ignition coil is housed in the distributor cap, which makes the GM HEI distributor a very efficient, self-contained unit.

Remove the primary lead from the terminal post at the side of the distributor. Disconnect the vacuum line if equipped. Remove the distributor cap retaining hooks or screws and remove the distributor cap. Note the position of the rotor in relation to the base. Scribe a mark on the base of the distributor and on the engine to facilitate reinstallation. Align the marks with the direction the metal tip of the rotor is pointing.

Remove the bolt that hold the distributor to the engine. Lift the distributor assembly from the engine. Line up the mark on the distributor and the one on the engine with the metal tip of the rotor. Make sure that the vacuum advance diaphragm is pointed in the same direction as it was pointed originally. This will be done automatically if the marks on the engine and the distributor are line up with the rotor. Install the distributor hold-down bolt and clamp. Leave the screw loose enough so that you can move the distributor with heavy hand pressure.

Connect the primary wire to the distributor side of the coil.

Chevy 350 Distributor Wiring Diagram

I would like to state that my truck is not computer controlled. If your truck has an ECM, I would not advise doing this because you will need to change everything. This is the only thing that is controlled electronically on mine. I decided to change this over to just a regular HEI without the ESC module and knock sensor since I had already done just about everything else. Below is a brief description of the ESC system. This will not affect emissions.

How do you hook up a HEI distributor on a 71 Chevy ? Answer. With new plugs and wires numbered, battery removed or both cables disconnected, install HEI with printed guide in front of you, insuring each step is read 3 times , double-checked, before connecting battery.

However in terms of high-RPM function, it falls well short of ideal. But before looking at the possible fixes lets consider why we might find it best to stick with an HEI-style distributor instead of just swapping out the entire ignition system. For a comprehensive guide on this entire subject you can visit this link: You can use the social sharing buttons to the left, or copy and paste the website link: Installation involves little more than just dropping the unit into the motor and plugging in one wire.

If you want to stray from my recommendations here, feel free to do so but consider this: There are a lot of fancy ignition systems available for the small block Chevy but the simplest and most cost effective is still the HEI—but it needs a little hopping up to get the job done. A custom built Performance Distributors unit takes care of that. Before going into a lot of details about what you can do and what you should do let me set the playing field here. There are a number of companies who are in the HEI business and I pretty much know all the bosses of all these companies.

I say this so you understand the fact that I am in a strong position to test all of the units involved. All of these companies make good stuff, but Performance Distributors has, by far, the best and most personal customer service.

HEI Ignition Tips for Your Engine

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