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1950 8 Cylinder Engine


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Am about to give up on the captioned. Each year the car fails to start, the points and plugs are replaced and the timing set. Car runs beautifully for about a year and then same problem occurs. While the car is running any acceleration at all produces profound spark knock, even with high test fuel.

MY QUESTION IS WHY IS THIS HAPPENING? <ul style="list-style-type: disc">[*]1950 8 Cylinder Problem

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Hello, Autosaur:

This sounds very much like a bad vacuum advance on the distributor. As the RPM increases, the distibutor advances the spark, but when you accelerate, the manifold vacuum drops, retarding the spark while you're accelerating to avoid pinging. You can watch this with your timing light. As the engine speed gently increases, you'll see the spark become more advanced, but when you hit the throttle hard, you'll see the spark momentarily retard.

If the vacuum advance is bad, you may have quite a vacuum leak through it which will make starting difficult. It may start when the ingnition tune-up components are all good and new, but as soon as they weaken just a little from use, they can not overcome the vacuum leak.

It's gross, but suck through the fitting on the vacuum advance and see if it's leaking.

New vacuum advances are getting hard to find, but Terrill Machine in DeLeon, Texas rebuilds them. (254) 893-2610

Let me know what you find.

JON

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Thanks so much for your help. It was indeed the Vacuum Advance, which has been sent to Terrill Machine for rebuilding. Should be smooth and dependable sailing from here on.

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Glad to hear I was of some help.

I see you live in North Carolina. My 1950 DeSoto Custom club coupe is an 8,000-10,000 mile-per-year car. I'm a native of California, but I lived in Concord, North Carolina for a time in 1995 with my DeSoto. I've crossed the country several times in this car with the only modification being a '57 Dodge rear end that lowered the RPM by 15%. I'm a big believer in using old cars daily, and I think Chrysler products of the Fluid Drive era are really underrated. They're good cars, and the eights can really get up and move when they're healthy.

Tell me how your car comes out with the new vacuum advance.

JON

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  • 4 weeks later...

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