vacuum or mechanical distributor?

[mygasser]

hello again everyone, hope you're all ok? i'm about ready to order the new dizzy and coil for my anglia and wondered what your thoughts were regarding vacuum or machanical only distributors. the car is a drag car only and when i build the stroker engine that will have more cam and the dizzy will go into that also. i'm leaning toward the mechanical only advance but would appreciate any input.
ps these are what i'm choosing from:- mechanical http://www.summitracing.com/int/parts/pnx-d7133800/overview/make/ford and vacuum http://www.summitracing.com/int/parts/pnx-d7133700/overview/make/ford
thanks in advance, neil  .

[e philpott]

skip the vacuum dist. it's for gas mileage ...... get the mechanical

[mygasser]

thanks, just what i needed to hear. it's confirmed my decision to go mechanical 

[ScotiaFE]

The cam you chose will also have a say.
A roller cam will need a steel gear. The harder roller cam will eat the softer
dist gears.

[mygasser]

 i knew about that mate, but thanks anyway i might not have done.

[Autoholic]

To build off of the recommendation on vacuum vs mechanical for anyone not sure about the use of each. Vacuum advance still has mechanical advance. The vacuum portion takes manifold vacuum into consideration for when the engine is idling and at partial throttle. It allows the distributor to add or remove advance based off of engine load, not just RPMs as a mechanical does. For drag racing, you don't need to worry about fuel economy. You're either on the throttle or you're not and RPMs is all that really matters when dealing with advancing the timing. So for a vacuum advance distributor, you'll have your initial advance + your mechanical advance + your vacuum advance for total timing advance when not at full throttle. At full throttle, a vacuum advance distributor works the same as a mechanical advance one.

http://www.pro-touring.com/threads/29320-Mechanical-advance-vs-vacuum-advance-article

Something to think about when going with a distributor is Petronix's ignitor 3. This electronic module takes the place of the points in your distributor and allows you to have a RPM limiter. The Ingitor 1 and 2 just replaces the points with electronic timing and they don't have a built in RPM limiter.

[Nightmist66]

I have used the Ignitor II and currently have the Ignitor III. No problems with either. Super simple and effective. I have the rev limiter set off right now with my mild hyd. cam.

[cjshaker]

If the car is truly drag only, unless you're leaving at idle or footbraking, have you considered an advance lockout with a start retard? If the engine is going to live at 2500-3000 and above, even the mechanical won't be doing anything.

[Falcon67]

I only run locked timing.  The Mallory 685s spark boxes are set for 10 degrees start retard.  The 302 is locked at 34, the 351C is locked in a 38 with iron heads.  Start them dozens of times a race weekend and drive one around on the street, no issues.  When you have a stall over 3000 or so, why would you need an advance curve anyway.  (the 302 flashes 4000, the Mustang 4600).  Locking in the timing makes them easier to tune IMHO, especially after you throw some cam at it.  I use a dial back timing light and it takes just seconds to dial in a particular advance.

Looks like an old stocker:


But only the base.  Locked advance plate, rotor phased, MSD pickup coil.  Home brew

[Faron]

Its the 9th and final round you have been Lucky / Good enough to make it here , and the Track round robins you since 5th round , your car is hotter , No biggie Dial up a few the starter points to you,  you hit the key / switch BUT because you have a locked out advance and the car is 180+ and your initial is 26 + BTDC it wont start , you watch the other car fire and take a single for the final , THAT is Why , and yes Ive been there , I was the car that Fired up , it was a 1687.00 dollar round win , keep your locked dists 

[Faron]

If its only a Race Car its up to you , if you can save money with a Mech Adv Only , Fine , Vac adv Only Gives you 1-3 MPG ( if its curved correctly ) wont make it any faster and of course takes up a bit more room than the Mech Only Unit

[Falcon67]

Its the 9th and final round you have been Lucky / Good enough to make it here , and the Track round robins you since 5th round , your car is hotter , No biggie Dial up a few the starter points to you,  you hit the key / switch BUT because you have a locked out advance and the car is 180+ and your initial is 26 + BTDC it wont start , you watch the other car fire and take a single for the final , THAT is Why , and yes Ive been there , I was the car that Fired up , it was a 1687.00 dollar round win , keep your locked dists 

Wrong.  I can fire the car for the final after hot lapping any day of the week.  180, 190, 200.  I can also cool the car in 3 minutes from a round down to the 170 staging temp.  When I'm back for the final - and I've been in a lot, 3 time footbrake champ, 2nd place this year by 1 round out of 1st - I'm usually waiting on the other car.  Oh, and the second place win was in a run off, best two out of thee with the other guy to break the tie.  Round robin/hot lap type run off.  Won on the 3rd pass ran dead on.  Lost the final in for the Iron Man this year on a hot lap to the final, last race of the year, ran UNDER the dial by .006.  I also run in some of the street tire shootouts - 10 mile drive, pull right into the lanes, make a run when you get to the head of staging.  Come right back, get laddered, run again.   When my car won't start, it means the starter fell off the car.

[Faron]

Good for You , But Not everyone's combo can , the point was , having an advance has a valid reason