Running smooth above 35 mph

M

Maurer1929

Member
My 1929 runs pretty smooth up to 35 mph and cruises well at 35 mph. It idles well too. Above 35 or so, it seems to get rougher but will easily go from 35-45. I usually don't drive faster than 45. I have a professionally rebuilt Zenith on it but engine hasn't been rebuilt in 30 years. Any suggestions on why it is rough 35-45 mph?
 
Loose center main bearing, or as was the case with my 29 Tudor, the center main was gone, as in NO babbit left. Mine really shook and made a racket above 20 MPH.
 
It is not that the engine is shaking, it is that the acceleration is not smooth, almost like the gas is intermittent or skipping.
 
Could it be out of time? Dirty plugs? Bad points?

These are just a few guesses from a no nothing Model A guy.
 
The classic cause of high speed power failure is insufficient gas. Do you have a fuel filter; if so, remove it! If not, look for fuel line obstruction elsewhere.

Disconnect the fuel line at the carb and observe the flow. It takes a surprisingly strong flow to get up to 45 and over. It should come out like a young man proudly writing his name in the snow; not an old man laboring to keep his shoes dry.

Otherwise, the sky's the limit on what might be wrong. We'll keep trying.

Steve
 
Could be lack of fuel, or lack of good spark. Do the easiest check first. Pull the coil wire and see if you have a strong blue spark by holding it about 1/3" from a head nut.

If you have a good blue spark, then I'd check for good fuel flow. Even if you find good fuel flow, you could have junk in the carb.
 
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