I have a rebuilt engine all assembled and just need a couple more things - one being the distributor. I am going to buy a new aftermarket HEI. The car is to be a daily driver when the weather is good, but I am considering running it at the local drag strip occasionally. A buddy suggested getting a distributor without vacuum advance, but his only real reason was that it is one less variable for the timing. I'd be interested in pros or cons either way.

 

Get one with vacuum advance. If you want to try stuff at the track then just unplug it. When you're wide open it's all back at it's base position anyway (no vacuum advance). Some people say they can "move around a little" even in their base position but I haven't ever found this to be true unless you're drawing down so much vaccum under the carb that it starts creating several inches of manifold vacuum. For instance, if your secondaries aren't opening you might see this problem at high RPMs. But if the carb is adequate for the application you'll never pull anything more than about an inch or so of vacuum in the manifold when wide open- well under what it takes to kick in the vacuum advance can (never seen one kick in at less than 3" vacuum).

 

Ditto what Damon said. I'm running vacuum advance on my "race car" because I also drive it to the track. Doesn't affect anything going down the track. Runs a lot better on the return road, in the pits, and in the staging lanes with the vacuum advance (I run mine on manifold vacuum).

Last time I ran a mechanical-only distributor was in 1977. I haven't missed it a single day since.

 

Thanks for the replys. Are there any advantages to a mechanical only?

 

all depends on how much advance you need and when you need it(at what rpm) youll have to find out by measuring how much advance you are getting and at what rpm's and then trial and error to find out if it wants/needs more or less advance at different rpm';s

each engine is differentand you have choicesof spring strengths and different vacuum advance diapragms, adjustable ones, stock ones, etc

good luck

 

In an extremely maxed-out, tweaky, race-only configuration, there is a slight advantage to mechanical-only. You won't see it hooked up in stock class NHRA cars, for instance.

 

Leaving off the vacuum advance also has the advantage (to the oil companies) of increasing your cruising fuel consumption by somewhere around 10-15%, maybe more in some combos.