Ignition Timing Issues
Thread Starter
Drifting
Joined: Aug 2021
Posts: 1,379
Likes: 955
From: Sacramento, Ca
Ignition Timing Issues
I have been doing some work on my fairly new to me 66 coupe just rebuilding and refreshing things that are in need and fixing many things that Bubba has had his hands on. The car has the 300HP motor. I found that the vacuum advance wasn't working so decided to remove the distributor and take care of any issues. I found that the advance springs had been changed at some time with two different springs. I replaced the VAC, made some other repairs and put it back in the car. I followed Lars suggestion of putting a timing mark at 36 deg. on the harmonic balancer and proceeded to set the timing. Lars recommends that the 36 degrees should be all-in by about 2800-3000 RPM. I am getting it all in with the springs that were in the distributor at 1300 RPM. I decided to buy the Mr Gasket advance spring kit and try new springs. No matter which pair of springs I put in, the best I can get is 36 degrees all-in at 1500 RPM. I'm thinking that maybe whoever originally changed the springs also changed the advance weights. I am contemplating taking the distributor to a shop with a distributor machine to get it dialed in, but wanted to ask the folks here if there's something I'm missing before I do this.
Thanks for any feedback.
Ted
Thanks for any feedback.
Ted
Tech Contributor
Joined: Aug 1999
Posts: 14,376
Likes: 6,375
From: At my Bar drinking and wrenching in Lafayette Colorado
That curve is too quick. Not even the factory hi perf distributors had a curve that quick, so somebody has done some funny-work to your springs. Find some old, used distributors with some big fat springs on them and try to get that curve slowed down.
Lars
Lars
Race Director
Joined: Jan 2003
Posts: 17,658
Likes: 3,665
From: Central Arkansas
If the weights have a shiny cadmium plating appearance they could be aftermarket. Stock one usually have a pretty natural steel appearance although they may have some sort of surface treatment. If you pull the distributor apart again, post a picture of the springs and weights. The heaviest springs in the Mr. Gasket kit should not be coming all in that quick.
Thread Starter
Drifting
Joined: Aug 2021
Posts: 1,379
Likes: 955
From: Sacramento, Ca
Gentlemen,
Thanks for the feedback. I didn't get a chance to work with the distributor today as I was working on some other issues. Hopefully I'll get a chance to get back to it tomorrow.
Lars - Ya, I'm aware that the advance is coming in way to quickly. I will see if I can locate some other springs. Have a couple of friends that may have some.
Dan - The weights are not Cad plated, just natural steel. I will take some photos when I get back into it.
Uncle Pasco - Yes, vacuum disconnected.
Again, thanks for the feedback. I'll report back when I have more info.
Ted
Thanks for the feedback. I didn't get a chance to work with the distributor today as I was working on some other issues. Hopefully I'll get a chance to get back to it tomorrow.
Lars - Ya, I'm aware that the advance is coming in way to quickly. I will see if I can locate some other springs. Have a couple of friends that may have some.
Dan - The weights are not Cad plated, just natural steel. I will take some photos when I get back into it.
Uncle Pasco - Yes, vacuum disconnected.
Again, thanks for the feedback. I'll report back when I have more info.
Ted
Thread Starter
Drifting
Joined: Aug 2021
Posts: 1,379
Likes: 955
From: Sacramento, Ca
I finally got back to working on the distributor this morning and have made some improvement. First off, I think I was mistaken when I said the advance weights were not Cad plated. They are not bright metal as I would expect Cad plating to be, but they are not natural steel either, so I believe they are plated and are probably after market weights as Dan suggested. I weighed the weights on my powder scale and an individual weight is 285 grains which equates to about .65 oz. I was hoping to find information about the weight of the original GM weights but was not able to find any. If anyone here has such info, I'd like to know. One issue I have is that the max idle advance I can get is about 12 deg (which I think is ok) because the VAC hits the intake manifold and if I advance the distributor one tooth it hits the coil and I've moved the coil bracket as far as I can. I am now at a point where the two best options with spring combinations will give me either 34 deg @ 2200 RPM or 36 deg @ 2000 RPM. I am going to see if I can locate some original GM weights, but until then, I've burnt up enough time screwing around with this thing.
If anyone has anymore feedback, I'm certainly open to it.
Ted
If anyone has anymore feedback, I'm certainly open to it.
Ted
Le Mans Master
Joined: Apr 2000
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From: New York New York
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As far as the can hitting, you will have to remove the distributor and rotate the lower gear 180 degrees, so the dimple is opposite the rotor tip.
You might want to find and old junk distributor and use the weights and springs to see if it solves you issue.
You might want to find and old junk distributor and use the weights and springs to see if it solves you issue.
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