Ignition Question

[TonyMadrid]

Hey Guys, I'm looking for a little help with ignition selection.
I am building a 351W backed with a C-4 Tranny. I've been looking at MSD and Mallory Distributors. What is the determining factor whether to go with mechanical advance or a vacuum advance distributor? What are the pros & cons of each?

Tony

[John Poling]

Tony,

Are you street driving or racing your car? I know that it makes a difference in this field. Having the vacuum advance will help the street mannerisms of your car to a point, if your drivetrain is to hefty, a vacuum advance may not do anything for you let alone that it may not work properly.

Vacuum advance will advance your timing at an idle so that you have better off idle reaction, this is why you remove the vacuum line from the distributor to set your initial timing. In a "race" drivetrain you would not need to run a vacuum unit because you would not be worried about your off idle characteristics.

Hope this helps.

John

[RallySnake]

Tony,

I highly recommend MSD over Mallory. Every time I buy a Mallory part, I end up throwing it away in disgust. MSD is still an independant company with strict quality control. They do what they're supposed to do and I have never had one fail.

If your car is to be street driven, the vacuum advance is important for good gas mileage. It advances the timing during low load, steady speed driving. With my new MSD vacuum advance distributor, the Blaster 2 coil, 8.5 mm plug wires and Holley 670 avenger carburetor. My 356 ci engine gets about 22 mpg at 70 mph with the Tremec in fifth gear.

If your car is race only, you don't need the vacuum advance, because it will be full throttle all the time (no vacuum).

Paul

[DAVID GAGNARD]

Tony;

I'll echo everything RallySnake said..... A couple of months ago my stock Duraspark distributor broke and I decided to upgrade to an MSD unit,I already have an MSD spark box.. I called the MSD tech line for info and the tech said for a street car they DO NOT recommend a mechanical advance unit,they recommend them for RACE ONLY vehicles... My car is a street car so I bought the vacum advance unit and love it.... Off idle acceleration is very good and so is the top end along with very good gas mileage.... There is no comparison between the MSD unit and the Duraspark unit,not even close.... I'm also running a 351-W..

David

[TonyMadrid]

Thanks Guys! Basic stuff that I should've realized. Guess I'm getting a little too grey on the top. DUH!

Thanks again!

Tony