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Old 02-27-2012, 02:04 PM
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lt1silverhawk lt1silverhawk is offline
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In regards to timing and fuel issues:

The next step is definitely adjusting the timing and a look inside the carburetor itself. There will be a few days before I will post back with any results on this.

-------------------- On a Separate Topic --------------------

In regards to fouled plugs, intake gaskets and vacuum leaks:

Originally Posted by sbchevfreak
Is it just me, or do the "even" plugs look to be badly oil fouled? If so, I would be looking at intake gasket sealing on that side....
Originally Posted by T-bucket23
Block off plates with that style choke dont go together at all. if the exhaust is not allowed to cross over it will take forever for the choke to open.
Originally Posted by T-bucket23
I would just to see if they [plugs] are black again. Could have been the choke fouling them
Originally Posted by ztwntyn8
I'd check the plugs first but a bad enough vacuum leak can cause hesitation and I've also experienced hesitation with too little base timing and that will def rob the **** out of your power and mileage.
Based on the above comments, I immediately had two questions:

- Would the intake manifold gasket that is not sealing correctly be causing both the fouling as well as any vacuum leaks?

- And if that is the case, then the intake manifold vacuum line routed to the transmission would cause it shift poorly because there is no vacuum source?

A quick search online led to the following passage:

Vintage Engines:

Automatic transmissions on many older vehicles use a vacuum modulator. It senses engine load by using intake manifold vacuum to tell the transmission when to shift. If the diaphragm in the modulator leaks, transmission fluid will be sucked into the intake manifold. This can produce smoke that might be confused with engine oil smoke, even though the engine may be in perfect condition. One clue is when the spark plugs nearest the vacuum tab on the intake manifold become oil-fouled with automatic transmission fluid (ATF). A leaking modulator diaphragm can also cause rough engine idle because it allows air to leak into the intake manifold. Harsh, late transmission shifts, or no upshifts, are other symptoms.

Be sure to question the vehicle owner thoroughly. The combination of any or all these symptoms can lead an owner to believe that an engine overhaul is needed. The key to diagnosing a faulty vacuum modulator is that the engine is probably consuming ATF and the level drops consistently.

From: "Automotive Engines: Diagnosis, Repair and Rebuilding" by Tim Giles. Page 58. Copyright 2010. Found online on Google Books:

Although it is not about intake manifold gaskets, the fore-mentioned quote echoes points raised by cobalt and Augusto on page 2of this thread:
Originally Posted by cobalt327
That vacuum line to the modulator valve- bend the hard line so it's pointing directly at the valve so the rubber hose connection is straight. It might be the photo, but the hose looks like it's becoming delaminated where it's bent. If there is any question, replace that length of rubber hose w/a new piece.
Originally Posted by Augusto
about the modulator's piece of hose, it's a good idea replacing it for a new one even though I don't believe that's is your problem, but let me tell you that I have seen modulators that fail, they get the internal diaphragm riped and let the engine suck ATF, that makes them smoke and run terrible. easy check, disconect the lline at the carb end and stick a piece of white paper, a napkin or something, it should come out clean, no traces of red ATF.

The transmission's poor shifting is one of the issues. I will be checking to see how the transmission fluid levels look, if the diaphragm is indeed working, and check the condition of the vacuum line. I will be able to report back on this shortly.

Last edited by lt1silverhawk; 02-27-2012 at 02:24 PM.
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