Distributor shaft length

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martin53

martin53
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Whats the length of the distributor shaft of a 1973 318. I want to convert it to electronic and a friend might have one but said there's different lengths. Also What years distributors are interchangeable. I wanna get rid of points
 
There are different lengths between SB, B, and RB, but not between small block. Look which way the advance sits......B and RB rotate the opposite direction

You can also twist the rotor. A small block (rotates clockwise) will "spring" clockwise, then snap back.

Any year smallblock distributor will fit any other year. Be sure it has a vacuum advance. "Lean burn" had no advance, at least some had twin pickup coils. You don't want them. Be sure it's not an "EFI" distributor, which has a great big half moon shaped "deal" inside. You want an 8 point reluctor, single pickup, and vacuum advance.

ANY factory distributor you get will need to be re-curved for performance, as any of them came with a "smog" advance curve.
 
The one I have sitting here is roughly 3 and 3/4 inches from the bottom of the plate where it sits on the block to the end of the shaft.

I have several smallblock dizzys from different years and they are all the same in length.
 
I have a duel pick up distributor with a vacuum advance. The distributor fits could I use it for now till I get another. I'd have to wire it though. What are your guys thoughts on this duel pickup
 
martin53 said:
I have a duel pick up distributor with a vacuum advance. The distributor fits could I use it for now till I get another. I'd have to wire it though. What are your guys thoughts on this duel pickup
Click to expand...

Not sure I knew that or not. You have to be careful. One or the other of the pickups is likely to suffer what is known as "ROTOR PHASING" problems

That is, the "wrong" pickup will not generate the spark when the rotor tip is aligned with the distributor cap contacts.

Google it. There are a bunch of various posts on the www

[ame="https://www.youtube.com/watch?v=aWMlNwGW0tM"]MSD Tech: Rotor Phasing - YouTube[/ame]

You might ask, "if one pickup has phasing problems, how was it ever used?"

Answer: That pickup was run through the fuel control computer, and controlled the spark advance by DELAYING the pickup electronically

This problem, phasing will actually be true of ANY dual pickup unit, vacuum or not. I hope I have not suggested something that will lead you off track

You mentioned you have a distro with locked advance. If you know that this once worked properly it would be a better choice.
 
cap off, install rotor & retract it all the way (if the weights ain't stuck the springs should already be retracting the weights (rotor). move housing to line up the magnet with the nearest tooth. snug down dist. make a mark on the metal dist housing rim plumb vertical down from the rotor location. install cap. make another mark on the dist top rim just below the CL of the cap bulge. take off the cap & see how far they are from each other. use the pickup that gets em the closest. the rotor has a wide blade and the cap terminals are wide so you have alot of leeway before the distance becomes too great for the available voltage to fire that gap. NAPA has an Echlin rotor with a .060" longer blade (MO3000) for $8 & change out the door or you can easily drill one out & add a longer blade your self (.015" clearance is ideal) this radial clearance reduction helps with the circumferential circular distance around the arc (they both add up). Note that vac adv will shift the phasing CCW on a SB from the at rest (no vac) position and an 8 deg (stamped) can will shift the rotor blade tip 8 degrees at full vacuum (cruising) or actually anywhere above what it takes to max out the can. the rotor will swing in an arc & I like it equidistant on either side of the cap terminal & definitely closer at WOT (no vac) in a perf app (when required voltage is the greatest)
 
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