Posted By: Moparmaniacc
Replacing dizzy - super easy question - 09/02/11 11:26 PM
I wanted to upgrade my modified stock dizzy with a MP unit so I could start playing with the total advance. I noted which way the rotor was pointed so I wouldn't drop the new one in 180 degrees out (this is a 400 BB). But the engine wouldn't start, just backfired thru the carb. Obviously the initial timing was wrong. I went back to the old one (which I have a little notch in at the base so I can put it exactly back where it should be) and everything was OK again.
If I put the new dizzy in again, this time ensuring the rotor points to the same wire on the distributor cap as the old setup, will that be close enough to get it started?
Posted By: screamindriver
Re: Replacing dizzy - super easy question - 09/02/11 11:35 PM
Play it safe and make it simple.....Bump it around until almost at TDC...Then watch{and stop} where the pick-up and reluctor line up{to fire #1}..Yank the old dist....Drop the new one in, line it up and go...You did check the pick-up clearance on the new dist....Did'nt you ???
Posted By: RapidRobert
Re: Replacing dizzy - super easy question - 09/02/11 11:39 PM
See if the tang on the bottom of the shaft & the rotor location phasing are the same in both dizzys. I would turn timing marks to 10BTDC #1 compression (15 if wild cam) & turn housing till vac adv is in it's general location w magnet lined up dead even w nearest tooth w the rotor at #1 cap terminal
Posted By: mikemee1331
Re: Replacing dizzy - super easy question - 09/02/11 11:45 PM
i don't see where you set the air gap..................
Posted By: RapidRobert
Re: Replacing dizzy - super easy question - 09/02/11 11:52 PM
After you turn the magnet dead even w the tooth/lightly snug the housing then set the gap to .008". No closer as vac adv will shorten that as it is on an eccentric plate
Posted By: mikemee1331
Re: Replacing dizzy - super easy question - 09/03/11 12:41 AM
if none of the above suggestions work it may be that the wire on the pickup are the reverse of what you had. its possible for the car to run (don't ask how i know) but will run like total garbage.
Posted By: Moparmaniacc
Re: Replacing dizzy - super easy question - 09/03/11 01:12 AM
OK it's running decent now, but the vacuum advance is pointing toward the front of the engine, rather than the driver's side valve cover like usual. Vacuum advance hose wasn't long enough so I ran it without it. Its dark now so I'll mess with it more tomorrow.
With the old distributor, I could not get the motor to ping. I could advance the timing to a certain point and it would be running decent, but if I tried to advance it further to get it to ping, it would start surging and not as much power. At first I used stock advance springs and then I tried replacing the thick spring with a Mr Gasket thin spring, same problem either way. Any ideas what was wrong with that stock unit?
Posted By: Moparmaniacc
Re: Replacing dizzy - super easy question - 09/04/11 03:42 AM
Thanks Rob, but I'm not sure I understood that. The new MP distributor is in, but vacuum advance is pointing to the front of the engine. How do I reclock it? Or could I just leave it the way it is?
(My question about the old stock unit and not being able to get the motor to ping was a separate question).
thnx
John
Posted By: 75DART440
Re: Replacing dizzy - super easy question - 09/04/11 04:49 AM
Move all the wires around the cap 1 or 2 holes to reclock. Example: if # 1 wire is at front, disconnect it, turn dizzy to desired clocking, and see which hole #1 needs to be in to still be at front. move wires accordingly.
Posted By: RapidRobert
Re: Replacing dizzy - super easy question - 09/04/11 05:19 AM
If you have room 2 turn the housing if need b & it's timed at ~ 10-15 BTDC & it runs good & total (check w vac adv plugged) is 36-38 & it ain't pinging you're good 4 now
Posted By: mikemee1331
Re: Replacing dizzy - super easy question - 09/04/11 12:30 PM
by any chance did the oil pump drive get moved when you pulled the dizzy? did the gear pull out along with the dizzy?
Posted By: Moparmaniacc
Re: Replacing dizzy - super easy question - 09/04/11 03:02 PM
No, I didn't turn the engine over while the dist. was out. And the gear didn't come out. (Big blocks have slot, small blocks have gear?)
I like the idea of just moving the wires, I think I'll do that.
Posted By: buildanother
Re: Replacing dizzy - super easy question - 09/04/11 03:44 PM
Both big and small blocks use the gear-shaft deal, but are different actual parts, turn in opposite directions. Sounds like you can move the wires over at least 2 positions clockwise, then turn distrib counterclock, so that is closer to where it should be pointing, towards drivers side of car.
Posted By: RapidRobert
Re: Replacing dizzy - super easy question - 09/04/11 03:59 PM
grab fan belt & turn it a bit (either way) till the magnet is lined up dead even w the nearest tooth then move the housing CCW till the magnet lines up w a tooth 2 teeth over then shift the wires back CW 2 terminals. This'll keep your timing near where it was so it'll start easy
only suggested it cause the last time i pulled my dizzy it pulled the drive shaft up enough for the gear to jump a couple of teeth which totally threw off my timing (or wire position, which ever way you want to look at it) 
