74 Vac' Advance

[Martin K.]

Does the standard Delco distributor on a 74 require ported or full vacuum.

[Craig S.]

Re: 74 Vac' Advance

Martin - I believe all engine options in 74 used ported vacuum off the Rochester carburetor for emissions reasons. The only full vacuum options were in the earlier years....Craig

[Jim T.]

Re: 74 Vac' Advance

I am sure your car came from the factory with ported advance, my 70 did four years earlier.
However the first modification I made to my new 70 was changing it to full vacuum advance 100% of the time just like earlier cars. I say earlier from 68 back, don't know how the 69 was configured. I did this in the first month of ownership and its still that way today.
Full vacuum will give better gas mileage in town. I went from about 11-12 mpg to 14 mpg in the city of Dallas and 18-19 mpg on the interstate at 70. Gas milage on the highway also went up when the speed limit was dropped to 55 on the interstates and highways.
Anyway your car should run more efficient with full advance.

[Martin K.]

Re: 74 Vac' Advance

Thanks for the replys, seems as though I can use either ported or full vacuum, ported being the original set up.