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Jegs Distributor |
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Jmerican 
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Joined: Mar/29/2016 Location: Seattle, Wa Status: Offline Points: 585 |
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 Posted: Aug/01/2018 at 5:03pm |
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No doubt the vac can has crossed my mind. The GM bases are covered, as there are many options for rate and total vacuum degrees. The Dura Spark units have options too.. Built in options, and easy cures to advance curve issues. As I ease back in to building these things again, the tricks come back. I like the MSD mag pickups, the Dura units, and a good GM unit too. I've noticed that many aftermarket units are not adjustable for vac rate and total.
In my experience the mid to late 70s Prestolite units can suffer worn bushings, then internal contact takes out the pickup. Then you are walking. |
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jpnjim
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Joined: Nov/25/2007 Location: New England Status: Offline Points: 2752 |
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Posted: Aug/11/2018 at 1:25pm |
I bought one of these when Ebay had 15% off the other day, knocked $19.50 off the $130 price  Got it today, seems to be a quality piece, even the cap and rotor seemed decent. Thanks again  |
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71 P-code 4spd Javelin/AMX
some Jeeps and some Fords |
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jcisworthy
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Joined: Jul/23/2009 Location: North Carolina Status: Offline Points: 2805 |
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Posted: Aug/11/2018 at 1:41pm |
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I have another one here also. It does not make sense to rebuild an old distributor anymore as far as I am concerned Jim
They take an MSD cap and rotor
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Specializing in dyno services, engine building, and cylinder head porting
rbjracing.com Phone Number 518-915-3203 |
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bobsterfl
AMC Nut
Joined: Jun/18/2009 Location: Orlando, Fl Status: Offline Points: 261 |
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Posted: Aug/11/2018 at 7:53pm |
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Great feedback; but as you know Jeg's does not manufacture anything, so this dizzy is made by someone else with the JEG's brand. This practice is not unusal, Summit does it as well, but I would be more concerned as to WHO is making it for them.
It certainly does look a lot like an MSD, but "Made in?????"
Here's what works for me. Delco points distributor on a 390 with an R4B and Edelbrock carb, mild (214/224) cam. I removed the rubber bushing from the advance stop and used a short piece of 1/4 inch copper tube to make a solid stop bushing. I had a bunch of springs and played around with them to get a maximum total of 36 degrees centrifugal advance at 2500 rpm. Advance at idle turned out to be 9 degrees BTDC. Just installed a Pertronix Ignitor III module, so we'll see how that works out. Then I swapped out the vacuum can for the beloved Echlin VC1765 unit available at NAPA stores everywhere. This can results in advance starting at 5-7 inches of vacuum and peaks out at 16 CRANKSHAFT degrees at at 11-13 inches of vacuum. The GOLDEN RULE for vacuum advance is to select a vacuum can that provides its FULL amount of advance at a point that is 2 inches less than your idle vacuum. That way the advance will be full on and steady at idle. So with this setup I have 36 degrees mechanical and 16 degrees vacuum at light load cruise for a total of 52 degrees. If that seems like a lot remember that as soon as you accelerate, manifold vacuum drops and the advance reverts to just the mecahnical. You really need vacuum advance, regardless of what the "experts" tell you. Engine runs cooler and is more responsive. Also, use full manifold vacuum, NOT ported. You want that extra advance at idle and ported vacuum won't cut it. Modern cars may not have vacuum cans, but they continually adjust advance based on engine speed (aka centrifugal to us) and load (vacuum to us). For a really helpful discussion on vacuum advance, please refer to this article written by Lars Grimsrud. http://outintheshop.com/faq/Vac%20Adv%20Spec.pdf There was also a great article in a recent issue of Hot Rod Magazine that is worth reading. Just IMO Bobster |
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Bobsterfl
1970 BBO Javelin 390 - Torqueflight |
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Jmerican
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Joined: Mar/29/2016 Location: Seattle, Wa Status: Offline Points: 585 |
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Posted: Aug/12/2018 at 10:58am |
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Bobster is emphasizing an important point. This is where a jeep dura spark type unit has worked well for me in the past. Lots of options for optimized cruise settings, with a lot of vacuum advance. Often overlooked in the hot rod community is light throttle cruise. Factor in EGR too. An engines' need under light load, and lean cruise can be high advance. Obviously this could be a term paper, so I'll leave it.
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WesternRed
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Joined: Aug/03/2010 Location: Australia Status: Offline Points: 5799 |
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Posted: Aug/15/2018 at 4:47pm |
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Holley has now added a new AMC distributor that is direct plug an play with the Sniper, things are getting interesting:
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1982AMCConcord
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Joined: Jul/13/2012 Location: Kenosha, WI Status: Offline Points: 1287 |
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Posted: Aug/16/2018 at 6:40am |
This is fantastic. Thank goodness. This is a giant leap forward for ANY AMC owner who is running the Holly Sniper stuff. I am quite amazed! I hope more companies start following suit. We need more good stuff for this brand!
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pit crew
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Joined: Jul/08/2007 Location: delete Status: Offline Points: 5341 |
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Posted: Aug/16/2018 at 7:33am |
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 73 Hornet - 401EFI - THM400 - Twin Grip 20 |
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jcisworthy wrote: