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Chevrolet - HEI DISTRIBUTOR INSTALLATION AND DISTRIBUTOR GEAR BREAK-IN | |
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This page gives the HEI distributor installation and distributor gear break-in procedures as altered by Chevrolet and based on the information GM supplies with the the P/N 93440806 GMPP distributor. Chevrolet has sought to take what GM has provided and improve on it with the hope that it will be more clear, and informative then the GM version. This is one of our information documents.
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INSTALLATION AND BREAK-IN PROCEDURES FOR HEI DISTRIBUTORS | |
| ACDelco # 93440806 | GM # 93440806 |
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HIGH PERFORMANCE HEI DISTRIBUTOR INSTALLATION INSTRICTIONS AND DISTRIBUTOR GEAR BREAK-IN PROCEDURE (READ fULLY BEFORE STARTING INSTALLATION) |
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| HEI DISTRIBUTOR INSTALLATION INSTRUCTIONS | |
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Step 1 - Unpack the distributor carefully and inspect it for possible shipping damage. Inspect again after removing the cap. If you are sure of or suspect there is any damage to the distributor, contact the place you purchased the distributor from before proceeding. You will have much less problems convincing the company you got it from and the shipper, if it was shipped to you, that the distributor was damaged when you got it, if you contact them at this point and not after it was installed and covered with oil or other signs of it having been used in an engine. Step 2 - If the distributor to be replaced has not already been removed from the engine, remove its cap. On GM HEI distributors, unplug the pickup-to-coil harness from the cap. Do not remove the plug wires at this time, but if you have to remove them, then make sure that you label each wire with their exact position that they are at in the distributor cap with using something like masking tape and a pen to write the information on the tape. Remove the wires one at a time as you label them. Crank the engine slowly until the rotor blade aims at a fixed point on the engine or firewall. Mark this point for future reference. You can use something like a Yard Stick (rulers are sometimes too short) or something similar to help you determine the spot on the firewall to mark if you are having problems eyeballing where the spot should be marked on the firewall. Step 3 - Find the connector in the wiring from the distributor to the ignition switch, and unplug it. Step 4 - Put a reference mark on the engine or firewall of the exact position of the vacuum advance canister, so that the new distributor may be easily installed in the same position. Step 5 - Loosen and remove the distributor hold-down bolt and clamp. Lift the old distributor out. If the engine had been running within the past few minutes, the distributor housing may be hot and coated with hot engine oil. Wrap a shop towel around the distributor to avoid burning your hands and dripping oil. Step 6 - Lower the new distributor into position. The rotor should be aimed at the same fixed point as was the rotor of the old distributor, and the vacuum advance canister aligned with the reference mark. After the new distributor has been lowered into place, you may find that it hasn't seated firmly against the support boss. This indicates that the lower end of the distributor shaft is not properly aligned with the oil pump drive rod. Do not attempt to force the distributor into position. Step 7 - Reinstall the hold-down clamp and thread the bolt just enough to exert a very slight pressure against the distributor. If the distributor was not firmly seated, manually rotate the engine until the distributor drops down into place. Step 8 - With the distributor properly seated, tighten the hold-down bolt just enough so that the distributor is held in place, but can still be rotated with a little effort. Again, make sure that the vacuum advance canister is aligned with the reference mark. Step 9 - Remove the plug wires one at a time from the old cap and install them in the corresponding positions of the new cap. If you had to label the wires, then follow your labeling to install them in the correct corresponding position of the new cap. (On GM HEI distributors, it will be necessary to transfer the coil and coil cover from the old cap to the new cap also.) After all of the wires have been transferred to the new cap, verify that the wire in the terminal post that is aligned with the rotor leads to the number one cylinder. If you are unsure of the number one position or firing order, this information can be found in the service manual that covers your particular engine. Now you can put the new distributor cap on your newly installed distributor. For HEI distributors, you must now plug the pickup lead connector into the new distributor cap. Step 10 - Reconnect the wiring leading from the distributor to the ignition switch. On GM HEI distributors, plug the pickup lead connector into the new distributor cap. Step 11 - Connect a timing light. Start the engine and allow it to warm up sufficiently to idle smoothly. It may be necessary to rotate the distributor (either clockwise or counterclockwise) before a smooth idle can be achieved. If the engine will not idle smoothly, the firing order may be incorrect or the rotor may not have been properly aligned during installation and is why it was so important to mark reference points as the installation proceeded. The error may could have occurred during labeling of the wires or if the engine wasn't idling properly before the install attempt, could be a sign the old distributor wasn't installed properly in the first place. At this point, you will need to consult a service manual for corrective procedures if you could not obtain a smooth idle. Once you have obtained a smooth idle, you can proceed to step 12. Step 12 - Consult the appropriate service manual to determine the factory-recommended initial timing and idle speed. Set initial spark timing with the vacuum advance line disconnected and plugged. Advancing timing two to four degrees from the factory setting will usually provide improved performance and fuel economy. However, timing advance beyond factory specifications may result in detonation, which can cause engine damage. Listen carefully to the engine. If you hear the engine knocking or pinging, retard initial timing as required to eliminate the knocking or pinging. Step 13 - If your distributor is equipped with a mechanical advance assembly, it is important to match the advance curve to your engine’s timing requirements. As an example of what this is talking about, MSD installs the heavy (slow) advance springs at the factory to lesson the chance of detonation in high compression engines, or those with power adders. For maximum performance, the timing advance curve must be optimized. Consult a service manual for instructions on setting the advance curve. |
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| BREAK-IN PROCEDURES FOR DISTRIBUTOR GEARS | |
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Important: Premature gear failure and resulting engine damage may result from failure to follow these precautions! 1) You should always replace the distributor gear with a new one that is the type designed for your camshaft whenever you install a new camshaft. Steel camshaft require a hardened or “Melonized” distributor gear. Also make sure that the new gear has the proper inside diameter to match the outside diameter of the distributor shaft. If the gear is loose or not fitting snugly, it will cause major damage to your engine. Ask your dealer for the proper gear for both your distributor and camshaft if you do not know with 100% certainty which gear you should use. The P/N 93440806 distributor comes with a Melonized distributor gear that is designed to fit this distributor correctly. If you hear any unusual noises during the break-in period coming from the engine, stop the engine as soon as possible and have it checked. 2) Coat the distributor gear thoroughly with a Zinc or Moly break-in lubricant prior to installation. Chevrolet can sell you GM P/N 12345501 Camshaft and Lifter Prelube if you don't have available to you. Comp Cams Pro Cam Lube or Camshaft Break-In Lube also works well. The Chevrolet Race Shop mostly uses Crane Cams assembly lube but only because they can get it by the pound and they prefer the tub it comes in to the tube that Comp Cams Engine Assembly Lube one pound size comes in. Crane Cams also has their Super Lube Break-In Concentrate that works well. Use whichever lube you trust and feel the most comfortable with, but you must use a lube for any new distributor gear installations. Please do not skip this procedure! 3) Chevrolet suggest a break-in period of one normal oil change cycle or approximately 500 miles as a rule of thumb. If a problem is going to show up, it will happen in a short period of time from installation and the cam and distributor gear should be broken-in by this suggested time. 4) Do not use synthetic oils during cam gear to distributor gear break-in. You should flush the synthetic oil from your engine if you have been using it then replace it with 30 or multi-viscosity weight oil (i.e. 30W or 10W-30). This grade of oil will provide the best break-in environment over other heavier or lighter engine oils. If you do not feel comfortable with this grade of oil due to weather conditions during the break-in period and you must use a heavier oil, then you may consider extending the break-in time to up to 2 oil change cycles but still checking the gear at the end of the first oil change cycle. Unless the oil is a real heavy grade, you probably won't need to worry about extending the break-in period. Use of synthetic oil during break-in should not even be considered as well as engine additives that claim to reduce friction in your engine. 5) For engines that are highly modified and have oil pressure exceeding 70 psi (cold), the gear should be broken in with a racing grade mineral oil. 6) During the break-in procedure the oil bypass should be removed (if your vehicle is so equipped) and the largest sized replacement oil filter that will fit where it is located should be used due to removing the oil bypass. Once the break-in procedure is over, then you can flush the non-synthetic oil you use for break-in from your engine and return to using the oil and oil filter you normally would be using. Never mix synthetic and non-synthetic oils. Remove as much trace of the one type of oil from your engine as possible before switching to the other type of oil. Also, replace the oil filter and do not reuse the old filter when switching from one type of oil to the other. 7) At the end of the break-in period, remove the distributor making sure you mark the position of the distributor like what is described in the distributor installation instructions above. This is to ensure that you will be able to properly put the distributor back after the gear has been inspected. Once the distributor has been removed, carefully look for any signs of wear on the gear and look for proper mesh, tooth alignment or excessive wear of gear teeth. If you are not sure what to look for, a service manual may be able to help you with this. If not, then take the distributor and gear to a qualified mechanic and have them inspect the gear. If the gear passes inspection, re-install the distributor, re-install the oil filter bypass, flush as much of the oil used during break-in from your engine (only needed if you are returning to using synthetic oil), replace the oil filter with a brand new oil filter that you would normally use, and you are ready to go. |
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| Note: Chevrolet has altered the distributor gear break-in procedure to make a little more sense and be a little more accurate. We have also made some wording changes in the installation guide which were only intended to make it clearer. Example: (to the new one) was changed to (to the new cap also) in step 9 and added in some more helpful bits of information. After these changes, we added information to make it more complete then it was originally. Though nothing is ever perfect, we hope that this is more helpful then what GM put out. | |
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GM Camshaft and Lifter Prelube P/N 12345501 Can be used for camshaft, lifter, and distributor gear installation. |
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