Duraspark distributor ????

Sure, you can do it... But you won't like the results. Vacuum advance is used to advance timing during partial throttle acceleration. Unless your distributor is set up for full mechanical advance, leave it connected.

that other distributor probably has no steel cam gear on it so be sure to swap the gear from the 85 to that one if you use it on a roller engine. don't unhook the advance, you will never get it timed right. either it will be to advanced and be very hard to crank or to retarded and backfire a lot.

You can simply remove the vacuum line and plug it at the source.

Then you will have only mechanical advance.

The reason people say this will be a part throttle driveability problem is because the vacuum is used at low rpm for advance and the stock mechanical springs do not provide full advance until 3000 to 4000 rpm.

You cure this by installing lighter springs.

You can set the max mechanical advance by using the desired slot on the advance plate.

This will cure the part throttle problem and give you full advance by 2000 or so rpm.

A loose converter and or big rear gears helps.

My 82 has had this for a year and had run its best with 6 deg base timing and 32 deg total, using the 13 L slot in the advance plate. I do have a 3k converter and 4.10 gears, so 800 to 2800 rpm is not important.

rd, is there a tech article somewhere on recurving the distributor in a step-by-step format? I've done several recurves myself, but only on a distributor machine. When you get them right, they're great!

Thanks for that link. Looks great!

It's also worth considering that with dissimilar springs, that you can recurve your distributor at different rates. Further, if you have the attachment tab bent on one of the spring attachments so that the initial "take-up" on one of the springs is retarded slightly from idle, you can have a multi-step, fully mechanical advance that is pretty similarly curved to a vacuum advance. The only place you're likely to suffer is in that "idle, to off-idle" range. This area is where you will experience (as discussed earlier) the potential for starting / cranking problems and also likely have the biggest affect on your fuel burn rates. If economy and / or emissions are not a huge deal to you (they probably aren't), then you may want to do away with your vacuum advance. I've kept mine hooked up, but only because I have a CraneCams Street / Strip adjustable distributor that allows me to electronically map my advance curve without having to monkey with springs, tabs, and keys. I love it! Good luck with yours.