Out of phase Pertronix?

Exactly. Is there no provision provided for letting you move one of the pickups relative to the other?

 

You applied the 2:1 crankshaft-to-camshaft relationship in the wrong direction -- 4 deg at the crankshaft is 2 deg at the camshaft so (using your diameter guesstimate):
2 deg correction/(3 deg/mm of movement) = 0.6 mm correction movement of the pick-up

If possible, make some reference mark(s) with a Sharpie before you move the pickup so you have a fixed reference for where it was.

 

How about the position of the distributor that no longer does any thing but direct the fire to 4 cylinders via rotor/cap. If this is not in the correct spot it could fire the plug ahead or behind the rotor when triggered via the other dizzy.
just my .02
ps old Ferrari wires love to crossfire

 

When I had my pertronix installed, the highly experienced tech told me why they couldn't be timed perfectly. For the life of me I can't remember why, but will PM you his contact details.

 

Have you tried calling Pertronix?

 

The small magnets within the sleeve have a bit of play and this can lead to a timing variation of 1-2 degree at the camshaft..

 

Why not just have two separate pick-ups, one in each distributor then? Problem solved....I just finished up an early 308 with that set-up. The timing bank to bank was perfect, as to be expected.

 

I'm not sure I understand completely; what you're saying is that through dumb luck swapping the two modules on their mounts solved the problem?
Although you had them installed in the locations provided by the factory?
And there are no adjustment facilities in the design?

When you took one pickup off during installation (is that unavoidable or required?) was it the one that was acting up?

 

David,

I'm thinking that the advantage of using one distributor is that only one centrifugal advance is being used, giving less chance for variance between two advances. Does that sound plausible to you?

Jeff

 

Jeff,
I agree completely that a single distributor solves one problem...and a considerable one. However, presuming (I know, a huge presumption) we have two distributors with matching curves, at least you'd be able to get either the initial or final timing to match. My impression was that the OP had two distributors with just a dual pick-up in one of them...

 

I plan to get one of these as soon as I get up the nerve.
I'll be sure to check how it works out. I wonder how many users have actually checked timing on both banks after installing one of these? It will be interesting to see if there's some variability to be on the lookout for, and then, if you find there is some, how to correct it.

What confuses me a bit (from looking at a photo on the Pertronix website) is how one Ingnitor works well in both positions, but the other only works well in one with no designed-in adjustment facility. Is there a possibility of wiggling parts to get that 0.6mm (0.023") slop?

Since they don't normally (I'd guess) build units with two pickups in one distributor, perhaps their standard tolerances aren't tight enough to prevent this? If you've only got one distributor and there's a few degrees error, you'll correct it by setting the timing. It's only when you try to synchronize two events through this mechanical relationship that it becomes an issue.

 

Greg,

I installed my recently purchased MR183 Petronix unit (and wrote a thread about it). I have been really happy with the improvement. However, I find that I have the identical problem you encountered- i.e. a few degrees difference between one bank's timing and the other. I timed the "driving" distributor's bank at 7 degrees BTDC, and checked the other bank. It was about 5 degrees off, say 2 degrees BTDC, very close to your findings.

I'll swap the pickups as you did and see what I come up with. I'm glad you posted this and found a simple solution. If the swap doesn't work, it is on to plan B, make modifications to move a pickup ever so slightly. (To folks considering this Pertronix system, this must sound like a pain, but it really isn't too bad- actually it is a refreshing change from fiddling with the dual points/dual distributors set up, at least for me).

Jeff

 

I followed up in another thread, but after I did my install (which involved a replacement of one of the modules), I checked both banks and found them equal.

 

As I mentioned I had sent my dizzy to Don King to set up and after I installed it the difference was 1* . I set the timing on 1-4 to 7*+ a little and got 6*+ on 5-8. 1/2* didn't make much difference.

 

I find it odd that they didn't include some provision for slightly moving at least one of the pickups in the design -- with the tolerances of all the parts and just the clearances between the mounting screws and the holes, it's impossible to have a "just bolt it together and all will be perfect" result. A couple~few degrees isn't much at the detector radius so maybe there's already enough slop in the mounting holes to improve the relationship -- just a thought...

 

Steve, I do too. Seems it would have been easy enough to slot one pickup. It would then be possible to loosen one of them and slide.

One thing I noticed when checking the timing stroboscopically (sp?) is that the indication was absolutely rock solid. In other words, the degree markers were not fluctuating at all when the light flashed. I'm used to seeing the markers twitch around some as the timing light flashes. It seems very precise in operation.

I'll post how I come out getting the timing synched. I'll try swapping the pickups if there isn't any play in the mounting holes for one pickup.

Steve, by the way, thanks for your analysis posted on another thread as to which pickup fires which bank of cylinders. That was helpful to me- got it wired up correctly first try. (The instructions from Pertronix suggest a trial and error approach)


Thanks, Jeff