vacuum advance kaput????

[billschroeder5842]

I think my vacuum advance is dead on my 75 road runner with a 400 4bbl.

I put a vacuum tester on the advance and I was not able to 1) get it to hold any vacuum pressure or 2) get the advance to move with the distributor.

My thought is that the diaphragm is broken. Isn't the arm supposed to move when you apply vacuum and fully hold pressure?

Any way to fix this? I DO have another distributor that I pick up tomorrow if this is unfixable.

So, IF I make a swap and the vacuum advance works, what should I notice? The car runs great, but lack a bit of power (compared to my 69 charger anyway)

Thanks!

[A383Wing]

it should move the arm and hold a vacuum...the diaphragm inside is shot....new vacuum canisters are available, but pricey for a big block

[billschroeder5842]

The parts store has a full distributor and vacuum for about 60. Not performance oriented but will fit the bill.

Will I notice any drivability things with a functional vacuum advance?

[A383Wing]

yes, better power on take off...better gas mileage...

[b5blue]

Strong advise not to use A1 Cardone reman. dizzy! (They are crap and will not match curve or advance for your car.) Repair vac. advance by matching new part to old. (Not hard to replace.) Never give up original dizzy as core no matter what!

[billschroeder5842]

Roger that.

Keep the core--I might do a rebuild at some point

Beware of anything A1 Car Done

This car is a cruiser--I'm under no illusion that this is a speed merchant. I've actually done the geeky emissions rebuild to bring it back to factory specs. I have everything back in place with the exception of the ERG value. I have conflicting signals on weather the car came with one to begin with(?). I have EGR hoses that have been sealed but nothing on the intake in the location from the shop manual.

My old charger was build to move quick while this RR is very 70's and disco.

[A383Wing]

intake could have been changed. Also, running EGR will also give better mileage

[billschroeder5842]

Successful installation!

The only change is that the timing went from 8 to 12. The motor runs great and idles at 800-850. I'd like to keep it at stock specs but I figure that 4 degrees after 40 years is acceptable.

I took it out for a quick spin-- I didn't notice too much, but that is okay.

Anything else I need to check or do?

[A383Wing]

difference in timing could be the little difference in arm length, or the stop the diaphragm rests on inside the can. You will notice a difference in how many miles you get per tank of gas.

I'm assuming you checked to see if it was working by using the timing light while revving the engine a bit from idle?

[billschroeder5842]

Yes, the advance does work and the diaphragm works and holds vacuum.

I have that OSAC valve so I'm not sure how that effects things. I'm driving it to work tomorrow (round trip 35 miles) so it will be a good test run.

[billschroeder5842]

Well, the first 17 miles in and around Dallas--- far so good. I notice a little more power and a little smoother on acceleration.

No mileage figures yet, but really I don't care.

[b5blue]

 

[c00nhunterjoe]

Keep the old one in the trunk... i know a solid handful of people that ran that distributor with multiple halk effect failures.