New member here!
Bringing a 1969 124 Spider convertible back to life. 56K miles showing on the clock, and it appears to have sat unregistered for 25 years. One of the previous owners installed an electric fuel pump. I've been going through the car solving wiring problems, replaced the cooling system, timing belt, ignition and spark components, and installed a 32/26 carb (re-jetted), complete brake replacement, drive shaft rebuild, new hoses... the list grows weekly.
I'm curious what the normal vacuum reading should be. It was reading 11-15 inches of mercury at idle. Car starts both cold and hot well. It seems to have a frequent stumble at idle, but it just seems to miss a beat. Doesn't appear to be timing. I need to figure out the fast idle adjustment and how that works with the choke. Can generally runs and drives well but has very little acceleration in the higher RPM range and I don't know if that is just what these engines are, if I'm missing an adjustment on the carb, or is there an issue with the vacuum advance.
https://drive.google.com/file/d/183Uocd ... sp=sharing
I have not done a valve adjustment yet, that is on the to-do list.
Normal Vacuum Reading?
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robh
- Posts: 3
- Joined: Mon Apr 14, 2025 10:47 pm
- Your car is a: 1969 Fiat 124 Spider
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18Fiatsandcounting
- Posts: 3911
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: Normal Vacuum Reading?
Welcome! Looks like a great project, and I have a fondness for the earlier years spiders (1969 to 1972).
Decades ago I had a vacuum gauge permanently attached in my '69 spider, and my recollection is that the vacuum was about 17 or 18 inches at idle. The engine was stock with the original 26/34 DHSA carb. 11 to 15 is too low, and there are a couple (more likely) causes:
1. Intake system vacuum leak, especially around the base of the carburetor, or in some cases, a leaking brake booster.
2. Idle mixture screw not adjusted correctly.
One trick is to connect a timing light with the pickup on the center wire from the coil to the distributor. You should see almost a continuous stream of light, but if the engine stumbles at the same time that there's a gap in the flashes, then that would point to an ignition misfire.
Where are you located? California, judging by the license plate, or elsewhere?
-Bryan
Decades ago I had a vacuum gauge permanently attached in my '69 spider, and my recollection is that the vacuum was about 17 or 18 inches at idle. The engine was stock with the original 26/34 DHSA carb. 11 to 15 is too low, and there are a couple (more likely) causes:
1. Intake system vacuum leak, especially around the base of the carburetor, or in some cases, a leaking brake booster.
2. Idle mixture screw not adjusted correctly.
One trick is to connect a timing light with the pickup on the center wire from the coil to the distributor. You should see almost a continuous stream of light, but if the engine stumbles at the same time that there's a gap in the flashes, then that would point to an ignition misfire.
Where are you located? California, judging by the license plate, or elsewhere?
-Bryan