Timing question?

Just acquired a holley 950 HP and it has no timed vacuum port. I've never run anything without one, so how do you work around this? Car will be street driven, so i'm not sure how important the vacuum advance part is. Can someone point me in the right direction on this?

 

Hi, it is a good idea to read through Larrys power timing thread. It explains the most (all?) regarding timing.
http://www.v8buick.com/showthread.php?t=63475

 

Vacuum advance IS important on street-driven cars. (see link in above post for the best info I've ever seen on timing your engine) As to your current situation - the simple solution would be to run your vacuum advance off a "manifold" vacuum port, rather than "timed" vacuum. In my experience, it works fine for a street-driven car - you just have to adjust your idle speed setting to compensate for the extra advance at idle. If you don't have a vacuum port of ANY kind on that particular carb, they make spacer plates with a built-in vacuum port. I've got one on my 350 between a 600 Holley and a T/A manifold. The plates come in many configurations and materials. Google "carb spacer plate with vacuum port" and you'll find several possibilities. You might look around this forum for more detailed advice on how to adjust your "tune" if you change the distributor advance vacuum source, and (if you decide to use a spacer plate) what kind of plate (open, center divider, 4-hole, etc.) would work best with your engine combo. Happy tuning!

 

Hi Christian, thanks for the link. That sure does answer my question and some I didn't have yet. :TU:

 

Chuck is right,,,,, if the carb doesnt have a port then just put a spacer under it that does.... or simply drill and tap into the intake manifold just under the front barrels so the vacume signal is strong.....
the vacume advance is huge as far as getting good gas mileage.... in the early 60's and back into the 50's all cars had a vacume fitting in the intake manifold for the vac advance.... direct port source.... you have full advance at idle and then in between idle and wide open throttle the vacume would build up in the intake and the vac advance would advance the timeing so that when cruzing at high way speeds you got good mileage....and good throttle response.... when you step down on the throttle , the vac drops and the vac advance retards the timing momentarily and then as the speed and vacume builds back up the timing is again advanced ......i have all my nailheads set up this way... they run strong and get good mileage .....

 

You're welcome, good luck with your tuning! :3gears: