captbone Posted May 10, 2010 Share Posted May 10, 2010 Gentleman Hello. I bought a B42T with a EN401. (I will post pics ASAP). It starts right up but you have feather the throttle and choke it to keep it runnig and accelerate. I am in the process of running seafoam, new fuel, replacing fuel lines and plugs. I have heard the increasing the fuel pressure can help this issue. How could I do that? Who rebuilds these Zenith carbs? How does the oil bath air filter work? Can I just install a K & N instead? Any help would be great!!! Thank you in advance! Quote Link to comment https://www.bigmacktrucks.com/topic/13834-en-401-carb-help-needed/ Share on other sites More sharing options...
Firemack Posted May 10, 2010 Share Posted May 10, 2010 Dieselman,We have a Zenith updraft on our B75 464 engine, it had similar problems and was caused by a bad accelerator pump (ball). We used a rebuilder that could also bench test the carb to make sure everything worked properly. Cost was about $400. I got it back and the truck actually runs better than when it was new, according to members in the company when is was delivered in 1954. I used Mark Buber Carb rebuilders in AZ. There is a list of suppliers and rebuilders on this site (from the Mack Museum) and Bubers contact info is on the list.I also changed the air filter to a K&N and works great. I called K&N and they recommended the filter based on dispacement, Horsepower and max rpm. I modified the original carb filter arrangement to use the K&N and kept the top of the Mack filter to looks like original. Good LuckFiremack Quote Link to comment https://www.bigmacktrucks.com/topic/13834-en-401-carb-help-needed/#findComment-54851 Share on other sites More sharing options...
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