HEI vacuum connections

[gmebey]

Thanks guys for all the advice.

As a short term solution I made the aluminum plate, and plan to drill/tap and plug the intake when I have time to remove it. Or even find one that does not have the EGR path.

After reading a few post on vacuum advanced HEI distributors it is clear that I need to know more about mine. I come by an article by Lars Grimsrud, "SVE Automotive Restoration" that peaked my curiosity. I plan to locate the ID number this weekend and look up the performance specs for it.

What would be a the ideal unit be in terms of pull-in vacuum and max advance angle?

As I mentioned in my earlier post this project is turned into a mess....Oh well that just makes this project a bit longer.

Again thanks,
Gerald

[Firebirdjones]

Originally Posted by gmebey

Thanks guys for all the advice.

What would be a the ideal unit be in terms of pull-in vacuum and max advance angle?

As I mentioned in my earlier post this project is turned into a mess....Oh well that just makes this project a bit longer.

Again thanks,
Gerald

Not sure I understand the question exactly but I'll assume you are talking about the vacuum advance only?

Vacuum advance is the last thing I'll set up on a distributor when tuning an engine.

The initial setting and centrifical is the first thing to attack, the most time consuming, and is the most important.

Without the engine being on a dyno it's hard to say exactly what the engine is going to like because there are a ton of variables out there, cam timing, compression, combustion chamber design, intake manifold runner length, stick or auto, heavy car, light car, rear gears etc.....so it's something you'll have to experiment with.

A baseline I like to start with on most older carbed engines is 14-18 initial depending on the camshaft, more cam likes more initial and produces more idle vacuum and helps the car idle more consistently.
From there I dial in the centrifical of about another 16-20 degrees depending on where the engine makes best power (this is where the dyno comes in handy) or you can use a dragstrip and tune with mph.
Once that number is found (lets say 36 degrees total for example) Only then will I dial in the vacuum advance for part throttle drivability. Again, hooked to a manifold vacuum source.

Now most stock vacuum cannisters usually have too much advance in them, some are 20 degrees or more. The number is generally stamped on the cannister. What I like to use is an adjustable vacuum advance because I only want about 15 degrees of vacuum advance at the most. Sometimes I find 10-12 degrees enough if the engine is finicky on pump gas and part throttle driving. Remember it's only working while idling and light to part throttle driving if hooked to manifold vacuum. At full throttle it's non existent.

Adjustable vacuum cans are available for both points and HEI distributors. Some are just a set screw to set spring tension inside the nipple for the hose connection.
Other more expensive and more precise units also come with a stepped key that bolts inside with the cannister and rubs against the advance plate (or breaker plate) to limit vacuum can travel, the more you limit vacuum can travel, the more it moves the breaker plate for more initial timing.
You can accomplish the same thing with a penny. Cut notches in the penny and drill a hole in it. Mount it the same way and it accomplishes the same thing.

Another tip, on older HEI's I limit the breaker plate advance (centrifical) buy installing a small stop screw in the breaker plate. Most HEI's OVER advance. The hole in the breaker plate is already there, so I just tap it for a #10 screw. I can then file on that screw and fine tune the amount of centrical advance I want in a particular combo. Some advance kits come with bushings, some don't, so I use the screw as a way around it.

Wish you were close by, I'd set it up for you. Hope this helps.