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Professional Tips

All of our products are engineered with the latest technology and thoroughly inspected with the utmost care and attention. If you still think you might have an issue, or if you have a question, please refer to this page. In the following topics, we will help you troubleshoot any possible problems and provide helpful technical tips for our products. If you have purchased one of our products and have a question or encounter a problem not covered here, please email us at for further technical assistance.

Topic 1: Excessive Distributor Gear Wear on Chevrolet

Worn GearProblems with irregular distributor gear wear can be caused by the distributor being “bottomed” out on the oil pump or cam walk. This problem can be easily prevented if the proper precautions are used.

First, we will cover the problem with “bottoming” the distributor. Bottoming of the distributor usually occurs when engine work such as the block, heads and intake have been milled. This will allow the distributor to sit farther down in the engine. The best method for checking the distributor to find out if it is bottomed, drop the distributor in the engine with no gasket. Also, make sure the cap and rotor have been removed for this test. Firmly hold the distributor against the intake with one hand and with the other, pull on the top plate of the main shaft. Very Important! Make sure you grab the top plate where the weights and center cam are riding. Do Not grab the reluctor (the part the rotor attaches to) because this part has up and down movement at all times. By grabbing the top plate you are checking for any up and down play in the shaft. If the shaft has up and down movement, you are now ready to install the distributor permanently by adding the gasket and installing your hold-down clamp. If there is no up and down movement in the shaft, then the distributor is bottomed on the oil pump. You will need to add a nylon distributor shim of correct thickness until the up and down play is achieved. Nylon distributor shims are available from Performance Distributors in thicknesses of .030″, .060″ and .100″. When the correct shim has been determined, add the gasket and proceed with the final installation. Always use a gasket with the shims. Warning! Do not stack gaskets in an attempt to raise the distributor height on the intake. Gaskets will compress and the distributor will eventually bottom out. Always use a shim when necessary.

Another method of checking for bottoming, is applying machinists dye to the distributor gear. Spin the engine by hand several rotations. Remove the distributor and inspect the wear pattern. You should have an even pattern through the middle of the gear. If this is not the case, add distributor shims until the correct pattern is obtained.

If you have checked the distributor for bottoming and you are still experiencing irregular gear wear, then the problem could be “cam walk” or “cam run-out”. This condition is where the cam is moving back and forth as the engine is running. Use of a cam button will help prevent “cam walk” but is not very effective if you are using a stock timing chain cover. The stock timing chain cover is made of tin and flexes easily, which can allow the cam to move even with a cam button. Use an aftermarket steel or aluminum timing chain cover that is reinforced for extreme cam loads. This should solve any problems with “cam walk”.

Topic 2: Excessive Distributor Gear Wear on Ford

Worn Ford GearExcessive distributor gear wear can be a problem with Ford engines. Most of the time, the problem is a result from the use of a high volume oil pump. High volume oil pumps put a lot of stress on the distributor and cam gears. A high volume oil pump is not necessary on a street driven engine that turns no more than 7000 rpms. Only extreme racing engines require the high volume pump. If you use the high volume oil pump the following precautions will save your distributor gear from early destruction.(1) Drill a .030″ hole in the lifter/oil galley plug behind the distributor. This will allow additional lubrication on the distributor and cam gears.

(2) Install a deeper oil pan. High volume pumps will pull all of the oil out of a stock pan creating a lack of lubrication.

(3) Ford oil pump mounting brackets have elongated holes. Due to this, the distributor shaft and oil pump shaft should be aligned so that the distributor turns freely before tightening the mounting bracket bolts. Failure to do this will cause a binding situation, thus damaging the gear.

(4) Stock Ford hex oil pump drive shafts are known to vary in length which could cause a bottoming or binding situation.

(5) Brass distributor gears can be used to avoid damaging the cam gear. Brass gears are softer and can wear out quicker than the cast gear, but will not cause damage to the cam gear. If using a brass gear, check it occasionally for wear.

Topic 3: Distributor Will Not Fire

If you are experiencing a no spark problem with your new DUI Distributor, the following information will help you check and test the installation, connections and components of the unit so that you can get your engine running and start Driving Under the Influence of more power!1. First and foremost, check the 12 volt wire that you are using for power to the distributor. This wire should be a minimum of 12 gauge and have no resistors in line. Make sure your 12 volt wire is fully connected to the “BAT” terminal, which is the terminal located on the front right of the cap. Also, make sure the three wire harness is fully connected to the three terminals behind the BAT and TACH connections. WARNING: If the hot wire is connected to the “TACH” terminal, damage to the module and/or coil can occur.

2. If all of your connections check out good, then check your battery voltage as you are cranking the engine. Since the DUI is a high performance ignition system it requires more voltage than a standard ignition system. If your battery voltage drops below 10.5 volts, this is not enough power to get the distributor to fire. This condition can be due to a weak or old battery or you are using a hot wire that has a resistor in line. Use a volt meter to test the hot wire while someone else cranks the engine over. If the voltage drops below 10.5, check your battery. 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. If the distributor fires using the jumper wire, run a new hot wire from your switched 12 volt source to the distributor.

3. A bad ground can keep the distributor from firing as well. The distributor grounds itself to the engine when installed. Make sure your ground to the engine block is secure. If the intake and/or the hold down clamp has been painted, remove any paint from the surface where contact with the distributor is made. To ensure a good ground, a secondary ground wire can be attached to the distributor by connecting a wire anywhere on the housing and running it to the chassis, body or negative side of the battery.

4. If you suspect an electronic part to be defective, the following steps will allow you to test the coil inside the cap and the magnetic pick up coil. You will need a ¼” nut driver and a multi-meter to check these components. To test the resistance of the coil, loosen the 3 screws (2 screws on 6 cyl. models) holding the top coil cover. Remove cover to expose the coil and you will see a red and yellow wire. Using the multi-meter on the ohms setting, touch the positive lead to the red wire terminal and the negative lead to the yellow wire terminal. The primary resistance value should be 0.6 – 1.5 ohms. To check the secondary resistance, remove the 4 screws that hold the coil in the cap. Pull the coil out of the cap and turn it upside down. 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. Your secondary
reading should be 6.0k – 10k ohms. (Click thumbnails for larger image.)

Primary Test
Primary Test

Secondary Test
Secondary Test

5. If the resistance checks on the coil are within spec, the next test would be to test the magnetic pick up coil. The pick up is located underneath the top plate of the shaft and has a green and white wire coming from it that plugs into the module. Remove the green and white wires from the module and touch the positive meter lead to the terminal on the green wire and the negative lead to the terminal on the white wire. The normal reading should be 800 – 910 ohms. (Click thumbnail for larger image)

Pick Up Coil Test
Pick Up Coil Test

6. The remaining electronic part that would keep the distributor from firing is the Dyna-Module. The Dyna- Mod 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. Unfortunately there is no test that can performed with an ohm meter on this part. You will need to remove it and take it to an auto parts store that has a module tester. Have them test the module 3 – 5 times as the module may not show to be bad until it develops some heat.

7. After you have conducted all of the testing procedures and you are still having a problem with the distributor, please call our tech line at 901-396-5782 during the hours of 9 am – 5 pm Central Time.

Topic 4: Oil In Top Of Distributor

Oil in the top of the distributor housing around the pick up coil and module is caused by too much crankcase pressure. The distributor does not suck oil up into itself. The shaft and gear only rotate, they do not force oil upward into the housing. The crankcase pressure forces the oil up into the distributor. The best way to eliminate the oil problem is to vent both sides of the engine. Moroso and Canton Racing Products both make a crossover tube with two breathers that allow you to breathe both sides of the engine. This crossover tube will not allow oil to splash out on the right side of the engine.

Another procedure to help alleviate the oil problem is to drill two oil relief holes in the distributor housing. First, remove the roll pin from the gear and remove the gear from the shaft. Be careful not to lose the shims and tang washer that are between the gear and housing. With the cap and rotor off, remove the shaft from the housing. On the housing itself, drill a 1/4″ hole into one side about 2″ up from the bottom of the housing. Do not drill all the way through, just to the center and back out. Make sure you drill above the two rings at the bottom of the housing. These are oil bosses and you do not want to drill into them. On the opposite side of where you drilled the first hole (180 degrees), drill another 1/4″ hole about 1″ underneath the flange that rests on the intake (where the hold down clamp is attached). Again, do not drill through to the other side, just to the center and then back out. These two holes will allow the oil to drain back down into the engine and will not hurt the strength of the housing.

One last procedure we recommend that is very effective and probably the easiest to perform is to fill four of the five slots around the bottom bushing with RTV silicone. The RTV silicone will stop most of the oil that’s being blown past the bushing from going to the top. Leaving one of the slots open will allow the bushing to receive enough oil to prevent any damage to the shaft or bushing itself. To perform this procedure you will need to remove the distributor gear by knocking out the roll pin. Once you remove the gear, keep all of the shims and tang washer together. Remove the main shaft. Use an RTV silicone (available at any auto parts store) to fill in four of the 5 slots around the bushing. The illustration to the left has the arrows pointing to the areas that need the silicone. Allow the silicone to dry completely before reassembling the distributor. Once dry, install the shaft and put the tang washer and shims back on in the order they were removed. Reinstall the distributor gear and you are ready to go racing!



Topic 5: Distributor Installation And Setting The Timing

Existing Distributor Installation

380000aIf you are installing a DUI distributor into an engine that has an ignition system presently, then this simple procedure will have your engine running in no time. On the old distributor, remove the distributor cap and the vacuum advance hose. Note the position of the rotor. We suggest cranking the engine over until the rotor faces the firewall and mark it with chalk. Remove the distributor hold-down clamp and bolt. Pull the distributor up and out of the engine noting the position of the rotor as the distributor clears the engine. With the cap off of the new DUI distributor, position the rotor to where it was when the distributor was just removed from the engine. Slide the distributor down into the engine. Be sure the rotor turns back to the original position (mark on firewall). If the oil pump drive does not engage, check that the rotor is pointing in the correct direction. If not, repeat the installation procedure. If it still doesn’t engage, bump the engine over until the distributor drive drops into the oil pump drive. Reinstall the hold-down clamp and bolt finger tight. Install the distributor cap and transfer the plug wires. It is recommended to open the plug gaps up to .055″ and this would be a good time to change them. We recommend setting your initial timing at 12 degrees BTDC while the engine is idling very slow (+ or – 600 RPM) and with the vacuum advance disconnected and the vacuum hose plugged.

Non Existing Distributor Installation – New Engine

If you are starting fresh and installing a DUI Distributor in a new or rebuilt engine, then you will need to bring the number one cylinder up to top dead center (TDC) on the compression stroke. Note: Make sure you are on the compression stroke or you will be 180 degrees out on the timing. If necessary, have someone spin the engine over while holding your thumb over the number one spark plug hole until you feel it “blow”, and this will be your compression stroke. Turn the engine by hand to line the timing mark up to 0 on the balancer. Once this is established, drop the distributor in the block (without the cap) and point the rotor toward the terminal you want to designate as number one. Once the distributor is installed and all clearances have been checked (see Topic 1), re-install the cap. Now, add the spark plug wires and follow the firing order starting with the terminal that was designated as number one. For optimum performance, set the spark plug gaps at .050″ – .055″. Leave the vacuum advance disconnected and plug the vacuum line. Your engine should now be ready to start. Crank the engine and adjust the distributor until it fires. Once the engine is running adjust the initial timing to about 10-12 degrees before top dead center (BTDC) while it is idling at 750 rpms or less. Once initial timing is set, lock the distributor down and recheck the timing. Plug in the vacuum line and go for a road test. Make sure there is no pinging under hard acceleration. If pinging is detected, retard the timing until it is eliminated.

Firing Orders Table

Chevrolet V8 (Small Block and Big Block) 1-8-4-3-6-5-7-2
AMC V8 1-8-4-3-6-5-7-2
AMC Inline 6 1-5-3-6-2-4
Buick V8 1-8-4-3-6-5-7-2
Buick Odd Fire V6 (225 ci) 1-6-5-4-3-2
Dodge/Chrysler (Small Block and Big Block) 1-8-4-3-6-5-7-2
Ford (Most V8’s) 1-5-4-2-6-3-7-8
Ford (5.0, 351C, 351M, 351W, 400) 1-3-7-2-6-5-4-8
Oldsmobile V8 1-8-4-3-6-5-7-2
Pontiac V8 1-8-4-3-6-5-7-2


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