Distributor questions
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Team Owner
Joined: Jul 2008
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
Distributor questions
My car is running like crap, so I wanted to start on the full tune-up procedure. I was under the impression that I was running points, so I went to take the points out last night and saw this:
Looks like a PO has swapped out the points for an electronic unit, yes?
So, no points, but I want to change that vacuum can as I suspect that might be the problem. The service manual I have is for '69 and covers Chevelle, Nova, Caprice and Corvette, in other words, it had almost nothing specific to Corvette, and it is the wrong year, so it wasn't much help. So my question is, how does this thing come apart to change the can? I had the mechanical advance weights off last night, but couldn't figure out how to get any of the rest of the stuff off. If I even need to change that electronic unit, how does it come out? Any help is appreciated.
Looks like a PO has swapped out the points for an electronic unit, yes?
So, no points, but I want to change that vacuum can as I suspect that might be the problem. The service manual I have is for '69 and covers Chevelle, Nova, Caprice and Corvette, in other words, it had almost nothing specific to Corvette, and it is the wrong year, so it wasn't much help. So my question is, how does this thing come apart to change the can? I had the mechanical advance weights off last night, but couldn't figure out how to get any of the rest of the stuff off. If I even need to change that electronic unit, how does it come out? Any help is appreciated.
Team Owner
Joined: Aug 1999
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From: Ontario
This pic shows the two slot-head screws that hold the vacuum can down. That looks like a Mallory electronic unit with which I am not familiar but I would imagine it uses the points screw-down holes.
Team Owner
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From: Crossville TN
To change it out [as intended], you have to disassemble the distributor. That requires you to drive the roll-pin out of the drive gear at the bottom of the shaft so that you can remove the shaft from the housing. Then, you need to 'walk' the little snapring out of the groove at the top of the [upper] housing bushing. It becomes easy at that point. By the way, I would recommend that you replace the signal wire in the dizzy while you are at it. That brass retainer clamped on the wire can cut through the insulation and short out the signal if it contacts any metal. At least, check it for shorts with an ohmmeter before you decide to re-use it.
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I have the same electronic unit on my car. It is a Unilite Mallory Infrared Unit. It has been running flawlessly for decades. If you suspect you have a bad vacuum unit test it. Get a timing light hook the vacuum unit to a constant vacuum port and see if the timing advances. If the can is bad you can change it without removing the distributor or Unilite. Push the breaker plate and loosen the vacuum can hold down screw. You will be able to disengage the vacuum can rod from the breaker plate.
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This is the link for the instruction manual for the Unilite, http://www.malloryperformance.com/pdf/501.pdf
Thread Starter
Team Owner
Joined: Jul 2008
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
If you suspect you have a bad vacuum unit test it. Get a timing light hook the vacuum unit to a constant vacuum port and see if the timing advances. If the can is bad you can change it without removing the distributor or Unilite. Push the breaker plate and loosen the vacuum can hold down screw. You will be able to disengage the vacuum can rod from the breaker plate.
Thread Starter
Team Owner
Joined: Jul 2008
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From: In limbo
St. Jude Donor '13-'15, '17 thru '22
By the way, I would recommend that you replace the signal wire in the dizzy while you are at it. That brass retainer clamped on the wire can cut through the insulation and short out the signal if it contacts any metal. At least, check it for shorts with an ohmmeter before you decide to re-use it.
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Race Director
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I agree and have done it multiple times, you do not have to remove the distributor. Remove the exposed screw. Push the breaker plate with a screw drive and hold it to expose the second screw and remove it. You can then wiggle the advance unit out of the distributor.
Team Owner
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From: Crossville TN
You can remove/replace the vacuum can without disassembling the dizzy (distributor). But, I thought I would provide the 'method' for unit disassembly in case the poster wanted to check out the condition of it while he had it out. [The 'spiral' snapring can be a real b!+ch if you don't know it's there.]