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Old 06-11-2014, 02:45 PM
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ksulliv ksulliv is offline
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'83 Carb Questions - Low Vacuum

The original carb on the '83 I bought last year had been re-built in July of '13. Even after the re-build it would not idle less than ~1200 RPM. Between the spring of last year and now, the plugs have been replaced, plug wires and distributor and it's still running points. I took the carb to a guy I know and he said that it was still gunked up so he got that cleaned up. With the idle screws out 5 turns (which seems like a lot to me) it idles pretty good, around ~800 RPM. It's still a little jumpy (ranges from 750-850 RPM), but overall, much better. Also the vacuum is still only reading about 14-15, which from what I read is too low. Vacuum is about 21 running in the driveway (no load) at 2K-3K RPM. I'd like the idle to level out a bit too but maybe I'm just being picky now. What should I look at first? Or am I fine, and should just leave it alone? Here's a quick video of it idling. Thanks!

http://youtu.be/VF0O7v5pHEU
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Old 06-11-2014, 02:50 PM
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The most critical part about rebuilding a carb is proper cleaning. Looks pretty good in the video. Nothing wrong with points - they work very well when set properly. How old are the points, and do you set with a dwell meter or just measuring point gap?
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Old 06-11-2014, 03:32 PM
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Quote:
Originally Posted by ksulliv View Post
The original carb on the '83 I bought last year had been re-built in July of '13. Even after the re-build it would not idle less than ~1200 RPM. Between the spring of last year and now, the plugs have been replaced, plug wires and distributor and it's still running points. I took the carb to a guy I know and he said that it was still gunked up so he got that cleaned up. With the idle screws out 5 turns (which seems like a lot to me) it idles pretty good, around ~800 RPM. It's still a little jumpy (ranges from 750-850 RPM), but overall, much better. Also the vacuum is still only reading about 14-15, which from what I read is too low. Vacuum is about 21 running in the driveway (no load) at 2K-3K RPM. I'd like the idle to level out a bit too but maybe I'm just being picky now. What should I look at first? Or am I fine, and should just leave it alone? Here's a quick video of it idling. Thanks!

http://youtu.be/VF0O7v5pHEU
Vacuum will always increase when the engine is revved. Vacuum is checked at idle and warmed up and is usually in the 14-18 in.Hg range, just depending on the camshaft and how worn out the engine is. You having 14-15 in.Hg vacuum at idle=no problem.
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Old 06-11-2014, 04:16 PM
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ksulliv ksulliv is offline
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The points are less than a year old were just set measuring the gap. I think my dad has a dwell meter so I could check them with that too.

Ok, that is good to know regarding the vacuum.

Is it odd that the idle air screws need to be backed out 5 turns get it to run properly?
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Old 06-11-2014, 04:53 PM
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Quote:
Originally Posted by ksulliv View Post
The points are less than a year old were just set measuring the gap. I think my dad has a dwell meter so I could check them with that too.

Ok, that is good to know regarding the vacuum.

Is it odd that the idle air screws need to be backed out 5 turns get it to run properly?
I missed that on the first post. They should be about 1.5 turns out. I would check for a vacuum leak. That would account for needing to back the mixture screws that far out. If no vacuum leak, your carb may still be gunked up and in need of a proper cleaning and rebuild.

Setting the points by gap gets you in the ballpark, but setting them properly may help smooth out your idle, and will definitely make them last longer an improve your performance.
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Old 06-11-2014, 07:29 PM
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ksulliv ksulliv is offline
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Thanks guys! I'll dig in to it a little more.
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