FWIW,typical performance Dizzys have less distributor advance and more initial timing for improved throttle response. That is why the RS is so popular. 24 deg of adv @ the crank and 10-12 deg @ idle for a total of 34-36 deg @ 5000 rpm or so. Depending on the engine specs, one can choose a more aggressive rate of advance.

The MSD unit handles all the advancement requirements electronically. No advancement is required from the distributor so a screw is installed in the advance plate in the dissy keeping it from moving. All programmable advancement is referenced from engine rpm then the logic controller sets the proper advancement so any thing is possible. Need a PC to set the advancement map. great leap in technology.

Sure would love to see those mysterious bushings that come up periodically. :rolleyes:

None in SC distributors; what year has these bushings? :confused:

Interesting...

Cant say I saw them, but it was included in the list of items replaced as part of the rebuild...

:confused:

The bottom area and gear of distributors is usually good because it's constantly lubed with engine oil. The top half of the shaft gets less and that is usually where a bushing is needed.
The upper half of the shaft is part of the centrifugal advance and needs a few drops of oil under the small felt periodically.
Lubing there is neglected by a lot of people and some felts are as dry as camel plop in the desert meaning: the centrifugal advance is impaired.

If radial shaft-play is excessive, bushings will have to be machined, the body bored out and all that adds to the cost.

You shouldn't just "lock down" a distributor. The rotor has to point at the plug wire when it fires. If you lock it down it will be off by at least 15 degrees at some point in the advance curve. This is why Carreras still have an advance mechanism inside.

-Andy

Andy,

Isnt the point of locking it down using the new Programmable 6AL-2 so that the MSD controls presicely when it fires to each plug?

The MSD controls the advance, if it wasnt locked down the MSD would not be accurate.

Shane

[QUOTE=snbush67;5268384]Never mind :

MSD is bringing their pro stock ignition technology to the street with their new Programmable 6AL-2! Since every NHRA Pro Stock car uses a Programmable Digital-7 Ignition Control, it was only a matter of time until MSD brought that technology to the street – and the time is now!


The new ignition, Part Number 6530, is based on the same output as the 6AL-2, but rather than rotary dials for rpm adjustments it sports a serial port that connects to a PC. Once you load MSD’s Windows based software on your PC, you’re ready to start mapping and programming. To start, you can get rid of the weights and springs that control the mechanical advance of your distributor. Go ahead and lock it out because you can now create a timing curve that allows you to manipulate the timing down to tenth of a degree increments every 100 rpm. The advantage is precise timing control, with the ability to ramp the timing in or retard it at exactly the rpm that you want it to move. Want more timing out for a start retard? Simply click the mouse and move a couple dots in position. Like a high speed retard? Clickity-click!

Take a look at the new CD-1 from Daytona-Sensors. Very similar and has other advanced features as well. Daytona Sensors LLC - Engine Controls and Instrumentation Systems for Automotive and Motorcycle Applications

Yes when I said locked down that just means the timing is set to TDC, and the mechanical advanced is disabled. The computer handles all advance and retard based on rpm and map (vacuum) inputs. the only thing the dissy does is distribute the spark, using the MSD unit.

When discussing "locking", we have to distinguish between different types of distributors and what it means.

Stock SC-distibutors have vacuum, a trigger plate and centrifugal advance.

Converting (Re-curving) a SC-distributor to run without vacuum, the trigger plate is locked and the weights/springs are modified for an individual set-up.
Locking the trigger plate means the centrifugal advance still works with a new curve according to specs like CR, octane and general temps.

I believe this also applies to distributors with points?
The trigger plate is locked, NOT the centrifugal advance. :)

Gunter,

I understand what you are saying, this is great advice to the OP.

I am interested in your thoughts about the MSD unit referred to above requires the springs and weights to be removed. Do you think it would be better to have this with a "Locked down" distributor or to have a stock distributor re-curved?

A programmable curve for about the same cost of a one-time distributor re-curve seems like a win situation.

Shane

The choice is entirely up to an individual.

I like to keep things simple and a Bosch CDI has been very reliable.
Bosch distributors have been running for a long time and I cannot see a great improvement in performance that would justify the cost of getting a complex system like mentioned above.

I can see twin-plugging when going over 9.8 CR, I can see re-curving a distributor to run without vacuum but, like JW, cannot warm up to MSD. It doesn't deliver that much more than the Bosch CDI, IMHO.

Of course, there is no limit to getting more stuff and doing more tweeking but, I am just happy with the extra 40 horses on my SS 3.2, 9.8 CR, 964 cams, SSI's, re-curved vacuum-less distributor, stock CDI, stock early CIS.

More driving, less puttering. :)

If I wanted more HP, I'd get a 964 or 993 and do some reasonable tweeking there.

The choice for me was simple; I did not have a distributor with an appropiate curve and nobody to re-curve it. I then retarded the distributor I had a bit to much and adjusted the timing to spec with the MSD.

Gunter - How do you like this engine? Why CIS over carbs? What mileage do you get? With the carbs on my 2.7, I get about 12.5 miles per gallon. This is because with my DC 40 cams, I can't run the engine below 2700 RPM, not purely the webers.

I think HP wise our engines should be close, but I bet yours is more street drivable.

If you "lock down" the dizzy so it points to the plug wire at TDC and then you advance the timing with a programable ignition it will fire the spark when the rotor is pointed about 15 degrees away from the plug wire at full advance. Again this is why the Carrera has a centrifugal advance even though it has a programable ignition and doesn't use the dizzy for ignition timing. The best you could do (and it might be good enough) is to lock it down at about 7 degrees before TDC. That way at low advance it will fire after the rotor points at the plug wire and at high advance it will fire before the rotor points at the plug wire. It should always be within 7 or 8 degrees and that may be close enough.

If the rotor is pointing to the plug wire at TDC and the ignition is firing the spark at 30 degrees before TDC the spark will be trying to jump with the rotor pointed 15 degrees away from the plug wire.

-Andy

great info even though i'm already set up

thx

[QUOTE=dicklague;5272250] Sounds trick...:) And about time!

Andy, this might help, with the MSD unit, set the timing 5 degrees BTDC like normal. The unit can be programed up to 30 degrees advance. After that, the rotor in the dissy will move too far away from the plug you want to fire (the limit of the MSD). Remember the dissy is moving at half crank speed so it should be enough advance timing (30 degrees around 6000 rpm for the unit to control) So the stock dissy limits the total spark advance. Anything higher and you have to go with a crank triggered unit. But it does sound like a good idea.

woops

12.5 M/pG for a 2.7 ?? A real guzzler. :eek:

I like the US '78-'79 non-Lambda CIS with the larger intakes, not the later '80-'83 Lambda version. I have an early CIS on a '82 bottom and a re-curved no-vacuum distributor. The 964 cam gives a little more lift and still allows the use of stock springs. Bosch CDI gives a very good spark and if I wanted more, I'd convert to twin-plugs.

Mileage is 23-24 per Gallon on the Hwy. cruising around 3200-300 RPM.
I wish for another gear when cruising.
This engine loves to rev and comes to live after 4k RPM; a very strong pull. :cool:

It's always weight vs. HP/Torque.

For better performance, I recommend reducing weight: Rip out the A/C, cruise control, heater blower.........................and, for the driver, a mostly vegetarian diet. :D