For those that have helped me I thank you very much.

So, I put the Holley 1945 back on. The 1920 is going to have wait until another day. There was a harsh flat spot off idle I couldn't live with for the time being and I don't need any new problems right now.

I plugged all the vacuum lines except for snorkel flap, choke takeoff, brake booster and distributor. So all the emissions stuff is temporarily inop until I can fix the stumbling and missing at idle. 3 different carbs make no difference so it has to be something else. Right now she is running great except for idle problems. She jumps off the line, no stumbles, and pulls hard thereafter.

Yesterday I spent an afternoon in the garage with my truck and found...

The 1945 has vacuum at idle. I'm starting to think this is by design. Can anyone with a similar truck chime in? Maybe I'm wrong and that is the source of the problem but anyway my timing at idle is over 20 degrees.

When I back the timing off, the idle improves significantly. But she doesn't jump off the line anymore. As I increase timing, the power gets better, but the idle downgrades. Catch 22.

Any sage thoughts? I was thinking tweak the distributor so the advance comes on quicker. That way I can have a decent idle and get the power back. I have the spring kit but haven't done anything with it.

With the vacuum advance disconnected and port on carb plugged, you have 20 degree's timing at idle?

Dave

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86 Miser 170,000+
2 1/4" exhaust
Holley 1920 #55
HEI MSD BLaster 2
17.8 mpg

No, it around 10 degrees less with vacuum disconnected.

You either are putting the vacuum advance hose on the wrong nipple on the carb or you have a 1945 that was intended for use with a lean burn computer. The lean burn computer systems used manifold vacuum to control the timing. Accoringly, the carb was modified to provide full vacuum at idle on the port previously used as the ported vacuum tap for the distributor. Unfortunately, there is no way to run the lean burn carb with a standard vacuum advance distibutor and still use the vacuum advance on the distributor.

If you truly have vacuum out of the distributor port on the carb (and your idle speed is low enough so tha tthe hoile in the carb throat is above the throttle plate), then you will need to either run a different carb intended for a vacuum advance distributor or run the distributor with no vacuum advance until you can get the 1920 on there and working.

My advice is to disconnect the hose going to the dist and cap the nipple on the carb. Run the distributor at the correct timing but without vacuum advance.

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Casually looking for a Clifford hyperpak intake for cheap.

Thanks, I'll try it Reed.

Another reason I removed the 1920 was the snorkel flap didn't work.

All the snorkel flap needs to work is a source of constant manifold vacuum. You could plumb it into the #6 runner vacuum tree.

Contact Aggressive Ted for tips on getting your 1920 working good. He is a whiz with his.

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Casually looking for a Clifford hyperpak intake for cheap.

Hopefully the 1920 just needs minor adjusting. It is a 'brand new' reman.

Right now, I got the 1945 adjusted to where it rarely stumbles at idle if at all and still drives ok. A little more sluggish off idle than she should be, but not too bad. My timing at idle is around 18 degrees advanced.

So sure this is temporary. And the advance cannot be tuned with centrifugal only?

I capped the vacuum advance port on the carb and set the timing to 12-14 degrees or so. I went high on the timing because setting it low causes a flat spot off idle.

Anyway, running good! Flat smooth power. Just doesn't pull as hard. I need to get the Holley 1920 going now that I know I have the wrong 1945 for my vehicle. I think the PO made many changes and I just have to unravel the mystery.

Sean,
Not a real mystery, look at the low speed bleed. Reference the manual figures.......Is the whole size very large?
If so, that is fine if your running a# 62 though a #66 jet. What that does is add more air to the emulsion tube. It works super for racing. Pulls hard a low rpms.

If your trying to run a #56 jet, seal the low speed idle hole.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

does your truck have the lean burn computer? I also have a 1980 and it doesn't. I'm not sure what mods were done over the years but from what i was told the only person who ran my truck was the original owner. I am currently having some problems after installing a rebuild carb but after poking around under the hood today i found my rotor button was damaged. not sure if this will help but I never saw it coming. It was running like the fuel pump might be failing.

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No computer I can see. I bought this truck a year ago. No telling what's been done. After removing the vacuum advance she's running pretty nice.

By disabling the vacuum advance that your mileage will suffer.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Can't be any worse than my 360. Anyway I'm going to run her like this for awhile and I'll start MPG measurements next fill up, which is today. What kind of difference would you expect in MPG with/without advance?

5 to 12 miles to the gallon.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I only recommended disabling the vacuum advance as a stop-gap measure while you source a correct carb. You should get the correct carb on there and get the vacuum advance working as soon as possible.

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Casually looking for a Clifford hyperpak intake for cheap.