1978 HEI Distributor Mech Advance Problem
Thread Starter
Burning Brakes
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From: Loir Valley Sarthe, France
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1978 HEI Distributor Mech Advance Problem
Hi
In a rare posting for me now, I need some help please! Haveing checked the timing on my '78 it appeared that the centrifugal advance was not doing all it should. On investigation it seems that the two parts that should move are not doing so! The picture shows the parts in question.
I believe that part A should rotate under Part B, that the weight base plate sits on. It will move rather stiffly, but not freely as I think it should. Any ideas on how I can free it up please. I have to say I'm trying/hoping to avoid removing the distributor at all costs!
Thanks!
In a rare posting for me now, I need some help please! Haveing checked the timing on my '78 it appeared that the centrifugal advance was not doing all it should. On investigation it seems that the two parts that should move are not doing so! The picture shows the parts in question.
I believe that part A should rotate under Part B, that the weight base plate sits on. It will move rather stiffly, but not freely as I think it should. Any ideas on how I can free it up please. I have to say I'm trying/hoping to avoid removing the distributor at all costs!
Thanks!
Last edited by Stephen Irons; Aug 26, 2009 at 10:15 AM.
Former Vendor
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
The arm A should float on the shaft. Rust must be between it and where it pivots on the shaft. The springs look like they have surface rust on them and this would be enough if present between the two parts to cause them to cease.
You can remove the weights, springs and the upper lobe and try to spry something in there to free it up. I hate to say it but if it were mine I would remove the distributor, then the lower gear. I'd pull the shaft for inspection, cleaning and reassembly. H
Willcox
You can remove the weights, springs and the upper lobe and try to spry something in there to free it up. I hate to say it but if it were mine I would remove the distributor, then the lower gear. I'd pull the shaft for inspection, cleaning and reassembly. H
Willcox
Race Director
Joined: May 2006
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From: Dayton, Ohio
If you shoot WD40 between the parts you can get it to free up but it will take lots of WD and lots of time. Keep rotating the parts back and forth. You are better off removing the dist and cleaning it good.
EDIT- I agree with Willcox , I'm a slow typer.
EDIT- I agree with Willcox , I'm a slow typer.
Last edited by ...Roger...; Aug 26, 2009 at 10:59 AM.
Race Director
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From: Dayton, Ohio
Stephen let me add the part that needs to get lubed and cleaned out is not the 2 horizontal pieces. What you need to lube is a shaft inside a sleeve and these parts run vertical. So the WD has to go in horizontal and then turn 90 degrees vertical to get to where it needs to be (and then that goo will then run down the dist shaft into the crankcase.)
Thread Starter
Burning Brakes
Joined: Jan 2001
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From: Loir Valley Sarthe, France
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Thanks guys. DWncchs, I guess I suspected that really, I just dreaded the thought!
So, if we assume that the distributor has to come out (agghh!) then is it safe to assume that I can turn it upside down and then spray WD40 on to the shaft and into the gap between it and sleeve? I don't have to dismantle the distributor right, or wrong! I'm not sure I'm that technical!
And another thought. As far as I can tell, the centtrifugal advance parts do not pull off the top of the shaft. Is that correct? That being so, what holds them on?
So, if we assume that the distributor has to come out (agghh!) then is it safe to assume that I can turn it upside down and then spray WD40 on to the shaft and into the gap between it and sleeve? I don't have to dismantle the distributor right, or wrong! I'm not sure I'm that technical!
And another thought. As far as I can tell, the centtrifugal advance parts do not pull off the top of the shaft. Is that correct? That being so, what holds them on?
Last edited by Stephen Irons; Aug 26, 2009 at 11:32 AM. Reason: Another question!
Former Vendor
Joined: Aug 2006
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From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Pulling the shaft out is simple and would allow you to polish the shaft and the inside edge of the advance plate.
When you have it out, look at the distributor shaft lower gear and notice the position of the dimple in it, this dimple should be on the side of the rotor button electrode. Make sure when you go back together you have this in the same position.
Knock out the roll pin and the gear will come off. Remove the springs, weights and the then you can slide the upper lobe off the shaft. Once this is done you should be able to separate the two parts. Clean and re-assemble. I have a picture of it apart if you want me to post it for you.
It's really simple to do and you can have this back together repaired in no time.
Willcox
When you have it out, look at the distributor shaft lower gear and notice the position of the dimple in it, this dimple should be on the side of the rotor button electrode. Make sure when you go back together you have this in the same position.
Knock out the roll pin and the gear will come off. Remove the springs, weights and the then you can slide the upper lobe off the shaft. Once this is done you should be able to separate the two parts. Clean and re-assemble. I have a picture of it apart if you want me to post it for you.
It's really simple to do and you can have this back together repaired in no time.
Willcox
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
B comes off, it is sitting on top of two pins. A will not come out unless you take the shaft out. The square plate with the pins for the springs is made to the top of the distributor shaft.
Willcox
Willcox
Last edited by Willcox Corvette; Aug 26, 2009 at 12:10 PM.
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,219
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From: Loir Valley Sarthe, France
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Willcox. Thanks! 
The exploded view is great. It explains the less than perfect picture in the Haynes manual!
OK, so assuming I move into the dangerously uncharted territory of distributor removal, there has top be a better way of seeing if the engine is at TDC than putting a finger in the #1 spark plug hole?! In the dim and distant past when I removed distributors from Minis (the “real” ones!) I knew which cap contact the rotor "arm" should point at when at TDC. Can I use the same method on the ‘Vette, and if so, which one should it point to?
You mention the "rotor button electrode". Am I right in thinking that's the same "arm" of the rotor, that carries the spark out to the cap? (sorry if that sounds dense!)
And, the next question…. The “roll pin” at the bottom of the distributor shaft. Can I re-use that? Will it “drift” out easily? Sounds silly, but these things are not available at “my neighbourhood Autozone” the end of the block here in France!
The exploded view is great. It explains the less than perfect picture in the Haynes manual! OK, so assuming I move into the dangerously uncharted territory of distributor removal, there has top be a better way of seeing if the engine is at TDC than putting a finger in the #1 spark plug hole?! In the dim and distant past when I removed distributors from Minis (the “real” ones!) I knew which cap contact the rotor "arm" should point at when at TDC. Can I use the same method on the ‘Vette, and if so, which one should it point to?
You mention the "rotor button electrode". Am I right in thinking that's the same "arm" of the rotor, that carries the spark out to the cap? (sorry if that sounds dense!)
And, the next question…. The “roll pin” at the bottom of the distributor shaft. Can I re-use that? Will it “drift” out easily? Sounds silly, but these things are not available at “my neighbourhood Autozone” the end of the block here in France!
Last edited by Stephen Irons; Aug 26, 2009 at 01:09 PM.
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From: mount holly NC
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Remove and replace distributor.
You can go to TDC on #1 if you want to but you can mark the base of the distributor and its position on the intake manifold, then mark the position of the 'arm of the rotor that carries the spark' on the top of the distributor. Then put it back in using those two marks. PG.
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 1,219
Likes: 448
From: Loir Valley Sarthe, France
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Thanks again guys! Off to "attack" it now!
