View single post by Gary Martin JH 15371
 Posted: 07-20-2009 06:46 pm
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Gary Martin JH 15371


Joined: 03-12-2005
Location: Portland, OR
Posts: 98
My car runs fine when cold and for first few miles. After driving two or three miles, it will start to idle rough,  then misses badly and occasionally coughs when talking off from a stop. Once it gets up to about 2300 rpm it smooths out and runs fine. It cruises fine. After slowing for a turn, it will buck and cough from 1500 to 2300 rpm again, then runs fine. It seems like a carburation problem to me. Engine is rebuilt, Strombergs are rebuilt, floats set correctly and carbs balanced. Carbs seem to tune fine and needle valves are set to datum. I run Chevron premium gas. Pertronix ignition with new wires and plugs. I thought it might have been the fuel pump, but I swaped the one from my spare JH and it made no difference.

Currently timing is set to 5 deg BTDC and total timing at 3000 rpm is 30 deg. Dist does not have a vacuum advance unit. If I set timing any more advanced (say 10 or 12), I get a lot of spark knock on heavy acceleration. So I backed off the timing.

One other wierd thing, every time the fuel pump clicks, the tach jumps up a thousand rpm and returns. Pump is stock SU type. Is there a fix for this ?