How To Set Timing On Sbc With Hei

I was checking the timing on my small block Camaro yesterday and noticed that the timing doesn't return to initial like it should. I set my initial timing at xiv degrees but then when I rev the engine and permit information technology fall back to idle, the timing light shows that the timing now is at 16 and sometimes xviii-20 degrees. If I rev the engine quickly, sometimes it volition come back to the original setting, but nearly of the time it does non. I take an aftermarket HEI distributor. Do I have to supersede the distributor?

J.V.

Jeff Smith: This issue could be caused by several dissimilar issues. Because y'all mentioned you have an aftermarket HEI, nosotros'll assume that it may be only a few years former. If the benefactor is original, manufactory HEI distributors from the 1970s and later were famous for issues with misfires that grounded through the shaft. Allow'southward kickoff with the older, used HEI's and then piece of work our way to the newer models. There are several things you can try to determine the real issue.

With an older HEI, start your diagnostics by removing the distributor cap and rotor. Expect inside the rotor for brown deposits inside the rotor. This is a mutual problem where the HEI misfires internally. Ofttimes the spark burns through the rotor into the mechanical advance mechanism on its fashion to ground. The brown material is fe oxide that has burned off the HEI shaft on its style to ground. Inspect the mechanical weights to see if they move freely on their pivots. Likely they will not motion freely. This can exist because the posts are highly worn from the spark free energy called-for them away. The brownish fe deposits are the consequence of this oxidation. If the posts are worn, this could cause the weights to stick. If the posts are worn, you must replace the entire shaft, which might cost more but buying a new benefactor. This is a very common problem but you might be able to find a used distributor with a adept shaft.

If the pins for the mechanical weights are a good shape, it'south possible that all you need to do is remove the springs and weights, clean and lubricate everything with white lithium grease to ensure the weights move freely. Often this is all that needs to be done. If the distributor is stock you might also consider adding a performance weight and spring package. There are several available through various companies like Accel, Moroso, Spectre, and Summit Racing to name a few. For example, Summit sells an inexpensive weight and spring kit (PN G-5212). Don't exist afraid to mix and lucifer the springs to go the curve you desire.

Another issue that can cause the HEI to be slow to recover back to base timing is a fleck more complicated, but easy to repair. Nosotros had an issue once with an Accel distributor that exhibited the same kind of problem. Nosotros removed the distributor and the weights and springs. Moving the advance shaft, the pin seemed very tight inside the slot and non easy to move every bit it should be. We removed the benefactor gear roll pin and removed the gear and separated the shaft from the benefactor. Even with the shaft out, it was still tight to move the limit pins inside the slot that limits the full mechanical advance.

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We disassembled our HEI all the way downward to removing the advance plate from the main shaft and discovered old grease had gummed up the advance plate, preventing it from returning easily to its base of operations, or starting position. Nosotros cleaned the former grease, added new white lithium grease, and reassembled the distributor to find information technology now works but similar new.

The advance slot master slice is retained by two small C-clips over the pins where the advance weights pivot. With the pocket-sized C-slips removed, we were able to detach the shaft from the plate and found the original grease used by the manufacturer had hardened and restricted movement of the pins in the slot. We cleaned all the old grease and re-lubed it with white lithium grease which returned the organisation to total freedom of movement. We re-assembled the distributor and put it dorsum in the car. We noticed that the mechanical accelerate now responded very quickly to engine rpm. In fact, it reacted so quickly that we had to add a slightly heavier leap to create the mechanical accelerate curve that nosotros desired.

Other practiced ideas to assistance tune upward your HEI include an adjustable vacuum accelerate canister. Many enthusiasts don't realize just how important vacuum advance is to street performance. For any engine that spends time on the street, it is to your engine's benefit to non but utilize the vacuum advance, merely to exist able to melody the amount of advance and its rate – or how speedily the advance is added and how much. Adjustable vacuum advance canisters are easy to spot considering the tin can is shaped like a hexagon with half-dozen distinctive sides.

You can arrange these cans with a modest 3/32-inch Allen wrench inserted into the vacuum nipple. By turning the adjustment clockwise, this increases the corporeality of accelerate. Turning the Allen screw counterclockwise reduces the corporeality of advance the can will deliver. Make adjustments two turns at a time as this should brand a measurable difference.

Many enthusiasts don't accept the fourth dimension to look closely at their parts to evaluate what's really going on. Often they just presume the parts are defective or broken and purchase a new one. If you take the fourth dimension to evaluate the parts you accept, you can often observe the simple issue and repair the problem while spending very little coin.

And that's something everybody can appreciate.

Writer: Jeff Smith Jeff Smith has had a passion for cars since he began working at his gramps's gas station at the age 10. After graduating from Iowa State Academy with a journalism caste in 1978, he combined his ii passions: cars and writing. Smith began writing for Car Craft mag in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his outset love of writing technical stories. Since 2003, Jeff has held various positions at Machine Craft (including editor), has written books on small block Chevy performance, and fifty-fifty cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves every bit a regular correspondent to OnAllCylinders.

Source: https://www.onallcylinders.com/2016/01/08/tuning-an-hei-distributor/