Should my handheld vac tester unit be able to pull open my vac canister on the Dist? Ive noticed about 20-25 vac reading on the guage and the vac canister arm has not moved a bit. Can those break or just plain not work? Do they adjust or does a person buy certain one for certain engine configuration? I cleaned up my Unilite Dist. and the vac canister doesnt budge. :sad:

The ones I've checked start moving at under 20" if I remember right. Haven't checked one in 4 years though...

Mine (msd) gives full advance at 15"

Their are lots avaialble, with different amounts and rates of advance. The aftermarket has adjustables, too.

It can be a lot more complicated than it needs to be. I'm not even sure the unilite uses a standard GM style can... Maybe call mallory and get a new one?

One thing for sure, is 25" won't move it, you do need a new one.

11" here.

I imagine she's dead jim. You should be able to pull and hold a vacuum...and it should move. You might disconnect it from the distributor and repeat the test to be sure something isn't hanging it up. Adjustability is very nice.

Its off the Dist. on the bench when I put the vac pump to it, wont budge even a tiny bit. Im taking it to mechanic for recommendations. thanks guys :thumbsup:

Agree with the others Jim - Replace it with an adjustable, they look slightly different with a hex shape front body but you can tune the amount of advance in and out of it. I'm sure they make a direct bolt in replacement for the one on your uni-lite. Summit, Jegs, and even Rock Auto should all have them...

ordered a new adj. vac unit from Mallory, local stores dont carry it and one even said 2 weeks time due to getting it from another source. I found one on google search at Amazon.com for $31 when O'Reilly's auto wanted $52. It will be here on Friday, so I can put it all back together. Now I need to read up on how to adjust it properly. Im open to ideas on that. Should I adjust it for least amount of vacuum or most amount of vacuum? :)

Start where it's factory set and go from there, should come with instructions, mine did. Basically follow them, add or remove advance based on test driving. Won't effect WOT but if you have a place you can lug it in OD and give it some gas to try to make it ping, a good stretch up a hill is ideal, be in OD before the hill at low RPM and ease into the throttle and listen. If it eventually downshifts and doesn't ping your good. Try to delay the downshift as long as you can but still putting a load on the engine.

I know you have higher rear gears so OD may not be the best test. Do the same in 3rd if you can't tune out any part throttle pinging.

Oh, you stick an alan wrench in the inlet to adjust the vacuum...

:thumbsup: thanks Dennis. There is a slow hill not far from me to use for testing. Got my allen wrench marked with tape too :)

There are 2 variables on vac canisters
1/the amoubt of advance determines by the length of the arm slot...this is not adjustable....thu it canbe extened, and stops mounte on the canister mounting screws will then make it adjustable
2/The point and range of vac the canister works at, this is the screw that preloads the spring inside the canister.
Every engine is individual in its requirements for both 1/ and 2/

when adjusting with 1/ this also adjusts 2/

I have never figured out why 1/ is not included in aftermarket adjustable canisters as this is just as critical, and allows for far better tuning...if the preload spring is in the right range...which often it is not.

As I think about adjusting. I haven't read the instructions, but. I think that I would initially set the adjustment screw so that full advance was at 1 to 3 in Hg numerically less than my idle vacuum. that way advance at idle is not influenced by slightly changes in vacuum. make sense, or am I all wet?

TTFN
Mat