Zachd

Engine runs fine at idle and 1k anything above while the vacuum advance line is plugged in starts to stalls the Engine. Which it unplugged it runs fine. Any info is much appreciated. 350 small block

oldcutlass

What distributor are you using? What is your initial and total timing without vacuum advance and with? In addition It could also be the plate ground wire is broken and when the plate moves it causes issues.

Fun71

What is the initial timing setting at idle speed with the vacuum advance disconnected?
Same thing with the vacuum advance connected?

Zachd

I converted the point ignition to electric while using the original distributor. Timing is set to 8° both with and without the hose plugged in because I'm using ported vacuum. If I use vacuum from the manifold it wants to die.
how would I check if the ground wire for the plate is broken?

joe_padavano

While I doubt this is the problem, simply connect an ohmmeter to each end of the wire. It should read 0 ohms. Now rotate the point plate back and forth to exercise the wire. If you get fluctuations in the resistance, the wire has an intermittent break.

Jelmoer

Did you use the same coil and vacuum canister?
Is it a coil that is powerfull enough for electric ignition.
Voltage oke at ignition/coil?
did it run fine with the points?
Changed points or more?
Proper Spark plugs and wire.
Is the canister not leaking?
Does the timing change at idle when put it to manifold vacuum?
Maybe the new ignition has an problem.

joe_padavano

Rather than making us guess, why not tell us EXACTLY what has been done to the engine? WHICH aftermarket electronic ignition conversion? What other non-stock things have been done to the car? What carb, intake, etc?

Zachd

Stock carb and manifold, I am using a conversion kit that just replaced the points specific part number from napa lx807. That's all I've changed. It does run rough when plugged into manifold vacuum. What is wierd is I changed out evrything early last year and drove without issues, it's only when starting it up for the first time this year is giving me problems

Vintage Chief

What year & model vehicle?

Zachd

1970 cutlass

Vintage Chief

Want to be clear we're on same page. You said stock carb - you have a Rochester, correct?

Zachd

Yes rochester carb

Vintage Chief

During your ownership have you EVER measured the vacuum with a vacuum gauge and adjusted the Rochester idle mixture screws? You have two of them. Each idle mixture screw should be adjusted to highest achievable manifold vacuum. You should be able to obtain ~17"Hg - 21"Hg. Has your vacuum EVER been measured?

Zachd

Yes I have, I tuned it last year

Vintage Chief

What was you measured manifold vacuum?

Zachd

I can't remember the specific number. I will have to look when I go work on it today

Vintage Chief

If you fail the 1st test (contained w/in the box) you need to further investigate. This test MUST pass.

gs72

Is your choke pull off working correctly?

Fun71

Does this conversion require full 12 Volts to operate, or does it work on the reduced voltage similar to points?

Zachd

Manifold vacuum was reading between 16 and 18 and jumping in between

Vintage Chief

Once again, you MUST pass the first test; and, to be of continued assistance, it's to your benefit to address the information provided. Did it or did it not pass the 1st test? I shouldn't have to ask again. You MUST pass the first test.
Jumping about between 16"Hg - 18"Hg isn't satisfactory. The needle should be rock solid steady.

Zachd

I tried getting the nettle as steady as possible and that's as far as I got. Wondering if I should have the carb rebuilt again

Vintage Chief

The reason the 1st test is critical is it demonstrates your vacuum capabilities. There are several devices dependent on vacuum. It isn't necessary we discuss each (e.g. transmission vacuum modulator, power brake booster, fuel-to-air manifold (atomized) fuel delivery via the carburetor, etc.). So, the 1st test becomes a key witness in demonstrating if you have a vacuum issue. When you measure vacuum you are (should be) measuring a closed/contained system - no open ports, no open vacuum lines, solid vacuum lines no leaks/cracks/kinks, etc. Vacuum should be tight and very responsive - immediate response as depicted by the 1st test. I'm not 100% vacuum is your issue but the tests don't lie. Re-read the diagram I provided it's a wealth of information.

If you had your carburetor rebuilt, when it arrived & you put it back on the intake manifold that is the best time to measure vacuum and make the necessary adjustment to your carburetor idle mixture screws. Those screws establish your best air-to-fuel delivery. I'll point out while yes they establish what is referred to as the "idle" air:fuel mixture that same fuel blend (air:fuel) is provided during idle, cruise & WOT. The "idle circuit" does function/operate throughout the full fuel delivery range (idle, cruise & WOT). If the needle is not rock steady and it jumps up & down 4"Hg - 6"Hg, you have some type vacuum issue & this can effect fuel delivery. A most likely suspect is air:fuel mixture is not adjusted for nominal performance. If you need assistance in establishing A:F mixture, we can assist. At the moment I wouldn't suggest having the carb rebuilt if it's already been rebuilt. Others have provided good information, as well. Is the choke pull-off operating correctly, is the high idle cam adjusted correctly, 12V constant, etc. Keep it simple start addressing some of the questions others have asked as well.

Finally, do you own the 1970 GM Oldsmobile Chassis Service Manual (CSM)? This is your bible when working on your entire car, including the engine (in particular).