'66 not idling, driving me insane.

[DukeGnarley]

So I just swapped out my old points carb for a new magnetic one. I think it's GM based.

Anyway, I can't get the damn thing to idle right, the lowest I can get it is around 1000 rpm. it will sound like it's idling just fine, but then will quite for whatever reason. I've tried messing with the timing without any luck, and I checked the fuel filter and it's fine. The car was idling fine a week ago with the old points dizzy, so I don't think it's carb related but at this point I'm out of ideas.

it will run perfectly fine above 1500 RPM.

After running the car for a little bit and warming it up, the starter will have a hard time turning it over for the first couple of compressions, then it will turn over quickly enough to start. It wasn't doing this before the dizzy swap, but I'm thinking it might be getting a little heat soaked because I've been running the car at a higher rpm in the driveway. I thought i would mention it in case anyone thinks it's related.


Carb is a manual choke edelbrock and the distributor is a professional products.

 

[JonK]

So I just swapped out my old points carb for a new magnetic one.

This was confusing me, obviously you meant points dist. What is your timing set at? Did you use a timing light or do it by ear? Increased engine temps are a sign of timing being off and would increase a heat soaked starter problem >starter gets hot and swells which slows down revolutions.

What did you do with the vacuum line that went to the points dist? Did you cap off the nipple at the carb? Is the manual choke properly adjusted?
Jon

 

[DukeGnarley]

you're right i meant points distributor.

currently I have the vacuum line plugged with a small screw driver, and I had set the timing at 10 BTDC however it was set at a higher rpm because I won't idle low enough. After that I messed with it by ear. then I dropped my timing light so it no longer works, I'll have to get another one tomorrow.

As far as I can tell the choke is opening up all the way. Like I said it was working fine before the distributor swap. I'll get another timing light tomorrow and try to set it again.

 

[horseballz]

Mr. Gnarely,
It definitely sounds like a timing issue, or maybe 2 or 3 timing issues. I couldn't find any actual instructions for that distributor (I assume #30001) but whatever instructions came with it should be read/digested completely. You need to find and/or set a baseline for the mechanical advance to find out where you're at, maybe even set it for O degrees mechanical/centrifugal advance just for starters and then dial it in from there. Just as an example, if it were a regular style Mallory mag distributor, out of the box you would likely get 10-12 degrees mechanical advance by the time you are at 1500-1600 RPM and when you add that to your desired initial timing you'd be looking at something like 20-22 degrees at 1500-1600 RPM and 22-24 degrees mech advance by 3000-3200 RPM for a total of 32-34 degrees, but if you don't know what the advance is supposed to be doing at that RPM your kinda shooting in the dark. Once you get your initial timing set, I recommend a timing tape (up to 40 degrees or more) for your damper and run the engine through the RPM range from idle up to the RPM that it stops advancing and check your advance at 200 RPM intervals IE: 1000-1200-1400 etc all the way up to 3000 or so to get an idea of your advance curve. I don't like/recommend an dial/digital/advance style timing light unless you can afford a really good ($$$) one, as they are notorious for inaccuracy.
Just My $.02 or Maybe $.03/$.04,
Gene

 

[DukeGnarley]

Thanks Gene, I looked at the instructions which shows a couple of different advance curves, including the one they set it up for at the factory. I can't lock the mechanical advance timing without removing the distributor from the engine. I think I will try to match the timing on the curve and time it at 2000 rpm and see if that works.

 

[horseballz]

Remember to add your desired 10 degrees initial timing to what they claim the advance is at 2000 RPM.
HTH,
Gene

 

[DukeGnarley]

Ok, according the graph of the curve, it should have about 2 degrees of advance at 500 rpm, and about 8 degrees at 2000 rpm. So I set the timing at 2000 rpm for 18 degrees, so it should be at 12 degrees at 500 rpm.

I slowly unscrewed the idle speed screw to bring the idle down, while watching the timing. at about 1200 rpm, the timing was around 14 degrees. Then at 1000 rpm the engine quit. I think I have the timing set right, or at least close enough to idle. What else could be going on?

 

[horseballz]

Did the unit come with instructions for checking/setting the air gap between the pickup and it's trigger? It's kind of odd that it is set up to advance at such a low RPM. Most performance distributors don't star advancing until 1000 rpm or more.
Gene

 

[DukeGnarley]

The instructions don't say anything about it. I'm wondering if it may be a voltage problem to the distributor. The distributor has one wire go to the + on the coil, one go to the -, and another that goes to engine ground.

I'm wondering if the distributor is getting the full 12v. Is there a resistor on the power wire that goes to the coil? I might try disconnecting the power wire from the distributor to the coil and jumping it straight to the battery.

 

[DukeGnarley]

nevermind, that didn't work.

 

[DukeGnarley]

problem fixed! the pickup air gap was too large. It now idles around 600 rpm. Thanks Gene!