timing with Weber's

[cab]

I got msd stand alone PN#8352 vac advance,I plugged the advance off and have the red bushing in it and blue springs .I set the at 10deg. and the red should stop at 28 deg advanced for a total off 38. but it only go's to 32 at 3000 rpm .

[Rick Parker]

Then dial in another 6 degrees initial.

[cab]

so that's it ,thanks I will give it a shot....

[bobcowan]

You could add another 6* of initial timing. That usually works well if you have a big cam. With a stock or near stock cam, then you might have trouble starting it on a hot day.

Your best bet is to work with the distributer and try to get 24* of mechanical advance, so you can set bas at 12*.

[Hans-Olof Blom]

How did you set the 10 degree? At idle?

At idle you can already have some mechanical advance.

You should set the total timing at an rpm that you know will give the total timing.

[MOTORHEAD]

You don't mention which engine you have, but if its a SBF, your initial timing should be more like 14-16 deg, then change bushing to limit total adv to 36deg.

[bobcowan]

Originally Posted by Hans-Olof Blom

How did you set the 10 degree? At idle?

At idle you can already have some mechanical advance.

I would hope not. Most distributers come from the factory with a curve that starts around 1200 rpm's or so.

[cab]

Originally Posted by MOTORHEAD

You don't mention which engine you have, but if its a SBF, your initial timing should be more like 14-16 deg, then change bushing to limit total adv to 36deg.

I do have sbf 289 and did put the red bushing in ,but if you just plug off the vac advance ,will that make it a mechanical dist. without any other changes .

[MOTORHEAD]

Craig:
I don't think just plugging the vac line is all there is to it. You should have an instruction sheet that gives directions on how to switch it over. If not, go to MSD's web site for it.

[MOTORHEAD]

Forgot to add that MSD's instructions give detailed info on how to set-up the advance curve with the different springs and bushings.

[cab]

the msd web site shows how to lock out the vac .so I have to do this when not use the vac and plug the tube . thanks for the help.

[Rick Parker]

I would hope not. Most distributers come from the factory with a curve that starts around 1200 rpm's or so.

Check the mechanical advance on ANY distributor OEM, MSD, etc. You will find that there is some looseness or "Slop" in the springs and their attaching points on the flyweights that will allow movement (remove the cap and rotate the rotor)that translates into approx 4-6 degrees of initial advance when the distributor first begins to spin. Then the inital resistance force of the advance springs marks the begining of the upward slope of the timing curve. In the case of MSD's the diameter of the chosen bushing (coded with various colors) limits the overall travel of the flyweights and reluctor (trigger wheel) to "Advance the timing".

[bobcowan]

If that's true (and I don't doubt you for a minute), then that small amount doesn't really matter. I never thought about it, but I'd bet I would lose a few degrees if I secured the advance weights with the engine off, and then checked it at idle.

That would still be included in the base timing, and so is not really advancing. I checked mine, and I don't see any true advance over base timing until the tach hits about 1,200'ish. Up until then, the timing stays right where I set it at idle (850 rpm's).

[cab]

So is this why Rick said to bump another 6deg to make up for the slop to get to my 38 .do i still have to lock the vac or just plug the tube.

[Excaliber]

Just disconnect the vac unit when you setting, adjusting and checking strictly the base plus the mechanical advance. THEN, after your done with that, plug in the vacuum unit. At that point, you can check it, observe it but it basically is what it is. Adjust your idle mechanical screws and carb air/fuel ratio idle screws last WITH the vacuum in place.

Vacuum advance with an MSD add's about 10-15 degrees or so, IF the unit does get the full vacuum signal. Actually that's not common under cruise conditions and impossible under any kind of throttle application when vacuum falls very low. So, under theoritcal ideal unlikely conditions your total would be:
10 plus 28 plus 15 (highest possible) = 53

Generally speaking 50 is about the max to shoot for, 53 is a tad high, but it's doubtful you will even see 50 under cruise conditions. Maybe under decelleration conditions when total timing doesn't really matter anyway.

I run 30 BASE timing and another 10 MSD mechanical advance. I use a custom CNC made limiter to stop the MSD mechanical advance at 10 degrees. I think the best MSD provides is an 18 degree limiter (black), to much for me, so I went after market.

My motor cranks fine with a stock OEM Ford starter even when the motor is really hot, like right after a couple of hard laps at the track.

[bobcowan]

Any slop that's in the timing mechanism is always there. It's included in base timing. Therefore, nothing to worry about, or compensate for. Although an interesting tidbit of info, not a whole lot of practical application. Set base timing at 10*, mechanical at 24*, and advance base timing as needed. Most of the time, there's no advantage to more than 36*.

MSD says they don't make a bushing to get less than 18* of mechanical advance. Where did you get yours? Did you make it yourself?

[Excaliber]

Got mine from a shop in Cottage Grove, Oregon. I'll have to look up the name and contact info if you want to get one. It's a "race shop", I've talked to the guy on the phone and he seems pretty good. He makes the CNC bushing for the MSD's because a lot of folks, like me, need less than the 18 degree's MSD offers.

Grab your wallet, if I remember right it was $40, but I got TWO bushings, so maybe it's only $20 for one? I forget...

Anyway, I NEED two, one for the MSD in the car now and the other for my backup MSD distributor. In case one breaks at a race so I can make a pitt stop and get back on the track.

Found the link to the shop:
http://www.4secondsflat.com/ Cool name for a shop I think!!

Looks like the price has gone up $5...

MSD Advance Bushings10* & 14*All MSD Distributors$25.00

[bobcowan]

Thanx for the link. I don't use a MSD, but I know plenty around here who do. That tid-bit could come in handy.