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Just Some Dude in Jersey
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Does the vac advance hold while it's running, but then bleeds down when you shut off? That would be normal.

Wow, no spark happening on that plug. It doesn't seem to be the long-threaded type. As mentioned, check to see if that plug is sitting deeper than the others. Maybe some knucklehead PO did a "mod". It's really REALLY unlikely that it's hitting your piston.
 

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Opeler
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I’ll be interested to see what happens when you swap distributors. I had one that the mechanical portion was getting stuck/not moving freely.

Good luck with this!
 

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Discussion Starter #45
Distributor swap will have to wait till tomorrow. O'Reilly's had the cap, but the rotor will be here tomorrow.

Guess I'll clean up the distributor today then. I hate to swap them. The one that's leaking is a reman that the PO put on.
 

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Super Moderator
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You’d need a fairly massive piston dome to strike the spark plug. Looks like it got bumped/dropped. No worries, just put in a set of fresh plugs and call it a lesson learned.
 

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Discussion Starter #47
You’d need a fairly massive piston dome to strike the spark plug. Looks like it got bumped/dropped. No worries, just put in a set of fresh plugs and call it a lesson learned.
Bob, I read somewhere that you said that vacuum pods should hold vacuum and if they leak down they need placed. Is this accurate?
 

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Bob, I read somewhere that you said that vacuum pods should hold vacuum and if they leak down they need placed. Is this accurate?
If you mean the vacuum advance diaphragm, yes, it should hold vacuum infinitely.
 
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Discussion Starter #49
Cleaned up the later distributor I had. Advance diaphragm held strong on this one. Replaced the ground wire on the breaker plates. O'Reilly's had a cap and rotor. And gapped all my plugs to 1mm.

Fired right up!

Adjusted the timing to 8° of advance at 900rpm. (Advance on my timing light.)

Runs great now. My son and I took her all over town. He's 12 and thinks the GT is the funnest car ever. Haha

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So what exactly was the issue?
 

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Über Genius
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So what exactly was the issue?
Seems all he needed to do was change the distributor.
Looking at the new one, it appears the lobes are the trigger for the mag pick up. Maybe the old dizzy had worn lobes.
 
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Just Some Dude in Jersey
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I'm hearing: Later distributor and diaphragm that holds pressure. I hear that the early distributors had a huge range of advance. If his vacuum advance was more or less not functional due to the the leaking diaphragm, maybe the diz timing would end up skewing wildly or not reacting hardly at all to vacuum........or loss of it. His problem occured when he accelerated and vacuum was low.
 

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One spark plug gap was closed so that had a huge drop in performance in one cylinder.
Post # 35.
 

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Discussion Starter #57
The plug was definitely why it ran so bad after the first Ingnitor III install.

The misfire, I guess, was a combination of timing, advance and maybe the missing ground wire.
 
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