Re: '52 200, ultramantic, runs rough at about 50mph or more

Posted by Bobby On 2012/9/11 12:20:07

Sometimes, things like this are like finding a needle in the proverbial haystack. To avoid frustration and that sense of overwhelm, what I do first is check the obvious, and in your case, that would be double checking the tune up (or other adjustments) you might have made...basically a re- do of the work. Start with the timing, if you installed points, that should have been re set, and make sure you put some synthetic grease on the distributor shaft. Tighten the wires, make sure the vacuum lines are in, etc.

Kanter makes a replacement glass bowl fuel filter with a paper element, get yourself one ($35), It's not worth the hassle to clean out the original and fit a new gasket, besides the paper element of a modern one is superior to the 60 year old porous one... just get to NAPA and have a couple of fittings available, the OEM ones are bronze so they'll likely split when you take them off.

Lastly, I'm not sure about diesel as an additive here..I know...'Reduces detonation and therefore knock', but it can't contribute to smoothness as diesel burns far dirtier (and therefore likely to plug) the spark plugs. Besides, the CR on your car isn't so high that you're in danger by using today's "Premium".

Lastly, check the trans fluid level...it's a long shot, but if she's low, you'd notice that as 'roughness' at higher speeds.