Re: intake manifold leak

Posted by Mike Flanagan on September 28, 1997 at 18:17:00

In Reply to: Re: intake manifold leak
posted by Dave Sturges on September 28, 1997 at 10:59:51

: Wayne,
: In addition to the great info Mike sent re your leaking manifold, let me offer my two cents worth.The highest possible vacuum is 21 inches.As Mike said, you will not achieve this I have seen readings on Model As of 18 to 19 inches.The gasket between the carb and intake manifoldcould also be leaking and play between the throttle shaft and upper carb housing will leak air.
: Dave.
You are exactly right dave. I was speaking to the most common source of vacuum leaks in the A. A good rule of thumb to diagnose problems in the throttle shaft is a pronounced "shortness of breath or coughing" when the brakes are applied sharply. The weight of the linkage and the shaft itself causes the shaft to move in it's bore ever so slightly causing a momentary loss of vacuum. And it is possible to bring an A "up to snuff", a friends '28 Roadster is so tight it pegs the gauge. It idles like a sewing machine... somebody should do something about people like that....
The Model A Fool.

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