Classic van running problems

[normspanners]

IMO float needle valve leaking causing over fueling----- catch 22 engine runs rough and vibrates making more fuel leak, making it run rougher etc etc
compressions will be down, due to bore wash, you clamped off the inlet which leaves the float valve out of the equation, and it runs better. answer to the issue.
had one few weeks ago on an elan webbers were flooding change valves perfect.

 

[keithski122]

OK, update on this.Sorry but no one wins the prize.
I haven't had a chance to look at this myself but the fuel pump was replaced which made starting easier but never cured the running fault.Dad found an article online about zenith carb problems and it turns out it quite common for the carb body to warp.He seperated the top and bottom halves wet and dryed them on a sheet of glass and bingo fault cured.He's already ordered a new carb (probably second hand) so is going to fit that.

 

[Nomad]

The update is appreciated - I often use older motors and it's always handy to know about faults & fixes.
Top marks to your dad for finding the fault, I have heard of warped carb/manifold face (maybe as a result of carb bolts being over-tightened) but it's not something I would have thought of.