I bought a used distributor (part# 1112002)and I think I need a new vacuum advance unit for it. It moves, but it seems to take a lot of suction to move it. I am having trouble finding a supplier with the right replacement. Will a vacuum advance unit for a 1971-72 350 4-bbl work on my application? If not, what will? I have a 1970 350 4-bbl (11/69 engine build)so I thought it might work. Please help.

Also, how can I tell if I need a new rotor for it? There appears to be nothing wrong with mine but maybe I missed something. Thanks a lot!

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1970 Chevy Custom El Camino aka Kaileigh
Green Mist & Silver w/Green Vinyl Top
350ci/300HP 4bbl & Factory Dual Exhaust
Non-SS with Factory Rallies!
TH-350 Automatic - 2.73 Posi Rear
My El Camino Home Page - www.dreamelectric.com (http://www.dreamelectric.com)

Usually when a vacuum advance goes bad, it's because the diaphram gets a hole. I think they are all kinda tough to move, especially if you are sucking on it yourself. I would bet it is OK. The rotor: look for a corroded edge contact.

To find a reasonble substitute advance unit take a look at yours and see what (if any) number is stamped on the flat part of it. This is the number of degrees of advance that it has. You may be able to match it to another new one.

Thanks, that helps a lot. I was testing it by applying suction to it like you said and since it took a lot to move it, I figured that the diaphragm was old and cracked or something and that's why it was difficult.

Is there any good way to replate the unit? I spraypainted it with Aluminum colored paint and that looks good but I'm not sure how long it'll last.

Shawn,
Believe it or not, I use an SOS pad and elbow grease to clean up mine.

When you suck on the vacuum tube and then hold your tongue to it, does it hold in place or creep back? If it holds a good vacuum, it is OK.

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Tom Parsons

Best way to test avacuum advance is to remove it from dis if not already off, push the shaft all the way in then place finger over the end and hold it to see if it leaks down. The rotor replace it. I've had one burn through under the center contact the engine backfired blew the muffler all to hell,and died in the middle of nowhere.Now I always carry a spare.If it is burned a little on the other contact no big deal thats from arcing inside the cap thats normal...FRED

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When I tested it, it stayed in place and didn't creep but took a lot of suction to get it to move. Sooner or later, I'll be taking my engine/tranny out to clean it up and while it's out I'll be switching the intake and distributor (it's a HEI & Edelbrock Performer now)with original ones. I'll also be using a Pertronix kit for it. My question is, is it hard to get the timing right when I put in this new distributor and will I have to adjust my carb settings with the new (cast-iron) intake? Thanks a lot.

Before you pull the present dist, bring the timing mark to 0 on #1 (be sure it's on 1 and not 6, pull #1 plug, put your finger over the plug hole and you will feel comp as it comes up to 0). Remove the dist cap and check the position of the rotor contact. Since you are also changing the intake, you can't make a mark on the dist base/intake joint. So make a mental note of the vacuum canister location. Put it all back together as close as it came apart. If it doesn't fire right off, have someone crank the starter as you rotate the dist left or right until it starts.
I wouldn't touch the carb setting at first. Drive it and evaluate for a while.

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Tom Parsons