Re: The Duchess Project: 1940 Super 8 Convertible Sedan

Posted by Joe Santana On 2019/6/7 9:06:04

QUESTION ON TUNE-UP: The professional shop initially set the dwell at 27 degrees. Idle was at 550 RPM. I asked that they set idle at 375 RPM.

They set the intial timing at 3.5 degrees BTDC. They set the idle mixture at HC 500, CO 3.0, A/F 13.6

At my request the set the idle speed slower at 475 RPM, cruise mixture is now HC 340-400, CO 1.30.

They said that setting the idle speed lower causes HC and CO to go up and idle won't stay smooth.

QUESTION 1: Are they imposing a new spec in doing the tune up where emissions take precedence?

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Driving home from the shop, the engine starts missing at around 40-45 MPH in standard 3rd gear.

QUESTION 2: Should they advance or retard the timing?

(In the meantime, when I got home, I set the idle screw at 375 RPM and the exhaust purrs like a kitten, just a smooth purr.)

MORE QUESTIONS:

Looking at attached photos, It does not appear that they changed the timing from when I brought it in? How are they setting the timing to 3.5 BTDC if not my rotating the distributor?

Please help me understand this.

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