Dwell is jumpin' 'round!! Dizzy?
Thread Starter
Racer
Joined: Jul 2006
Posts: 266
Likes: 1
From: S.E. Michigan
St. Jude Donor '07-'08-'09-'10
Dwell is jumpin' 'round!! Dizzy?
I'm having the proverbial 'one-thing-after-two-others' problems. Car wouldn't start; did the basic tests, no fuel into carb. Rebuilt carb. Starts OK, choke problems, but starts OK. Idles very rough, set dwell to 30. It's jumping around between 25-35 at idle! New points, so I guess I'll pull the dizzy for a rebuild?! 
Ideas?
Ideas?
Melting Slicks
Joined: Jul 2004
Posts: 2,867
Likes: 195
From: Maryland
End gear should be shimmed to .002"-.007". A distributor rebuild might be in order as it probably hasnt been maintinanced in a while. Use 28-32 HD points, HD cap , rotor coupled with a correct VAC. Find a person with a good supply of springs, weights , autocams
and a Sun Distributor machine and setup the ignition curve to performance specs.
You must establish a good ignition baseline before you work on the fuel system.
Last edited by Donald #31176; Jun 12, 2007 at 04:12 PM.
Thread Starter
Racer
Joined: Jul 2006
Posts: 266
Likes: 1
From: S.E. Michigan
St. Jude Donor '07-'08-'09-'10
I just remembered... I checked vac and at 'idle' I was reading around 15. Granted, my 'idle' was pretty jumpy! Couldn't check the timing setting. BTW - '71 SB
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Try opening dist cap window and grounding points plate to engine block. My best guess is that your grounding wire is broken between the points plate and the distributor housing. This happens to people who install Pertronix Ignitors and they then decide the Ignitor unit is aa piece of junk rther than properly disgnosing the problem. You can run temporary wire through the cap window but to replace it, you need to tear down distributor completely.
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Thread Starter
Racer
Joined: Jul 2006
Posts: 266
Likes: 1
From: S.E. Michigan
St. Jude Donor '07-'08-'09-'10
Try opening dist cap window and grounding points plate to engine block. My best guess is that your grounding wire is broken between the points plate and the distributor housing. This happens to people who install Pertronix Ignitors and they then decide the Ignitor unit is aa piece of junk rther than properly disgnosing the problem. You can run temporary wire through the cap window but to replace it, you need to tear down distributor completely.
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
SIXFOOTER: On a GM HEI dist, what is the end play supposed to be? The same .002 to .007?
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,392
From: At my Bar drinking and wrenching in Lafayette Colorado
The lower bushing gets the wear, and it can't be checked without pulling the distributor out. With the distributor out, just grab the drive gear and see how much side-to-side (radial) movement you get. There should be none.
Le Mans Master
Joined: Dec 2006
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Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
don't ask.....
anyway, they can get highly intermittant, with the broken wire inside the black plastic/rubber surround....all you need do is pull the cap and the rotor cap, and locate the wire...tug on it, and if it gives up you know the super thin flexible copper wires inside are toast....
replace it...NAPA should have one....