new engine - old problem

ole39

ole39

Senior Member
well, after 2 1/2 years, got the old girl running, 8ba, new pistons, rings, bearings, lifters. it is 1/8th over, 400jr, stock dist, soon to be replaced by an old rebuilt mallory dual point, and a rebuilt 94. runs fine till 1/2 throttle, then falls on its face, acts like choke is partially shut. this is same thing that was going on before rebuild. plugs, wires, cap, points cond, all new. been searcing archives, and some one mentioned ignition switch, what say you oh flathead gurus?
 
To eliminate the switch use a clip lead to jumper the switch out. Does the problem show up absolutely dependant on throttle position or is it engine speed related?
 
might need more info, is it a shoebox Ford with overdrive? or a 8BA in a early Ford. when you say "falls on it's face" does it miss or die or just run out of power?
 
Have you checked fuel pump volume? Sometimes the flex line between the fuel line and the pump goes bad and doesn't allow enough fuel to flow. There could also be a restriction between the tank and the pump. I would also put a timing light on it and see if you are getting any ignition advance as the engine revs up. Is the gas cap vented?
 
Have you checked the timimg with a timing light. If the timing is way ahead, like 30-35 degrees the engine will break up bad at high rpm. Walt
 
check muffler it could be plugged, take exhaust pipe off in front of muffler and run it down an out of the way road, dont want to irritate the man, lol
 
ok, engine is in a 39 2 door, timing is set as per marks, original gas cap, does this with or with out cap, no mufflers, open headers, 3/8 fuel hose from tank forward, checked advance with timing light, it advances. have not checked pump volume yet. 'falls on its face' misses / runs out of power, had stock dist checked out, also put on new vaccum pot, checks out ok. one thing i forgot to mention, when the vacuum advance is pulled, then it runs ok, but drinks gas, the plot thickens.
 
It appears you've diagnosed your problem and it's timing. When you "pull" the vacuum advance, are you advancing or retarding the spark? With the other modifications you described, I think a different distributor/ignition system would serve you well as opposed to the stock unit - which isn't the greatest, at best. Randy/In has a good point. The stock distributors only work properly with the proper carb which has a vacuum port in the body.
 
if it runs ok w/out vacuum hooked to distributor, there is a chance the wire that goes to the points is worn bare and is grounding out to the dist. body when the advance moves the breaker plate. just a thought...jack
 
vacuum comes from carb. yup rubber gas line, temporary fix. will check for bare wire in dist. ive had 2 different stock distributers in, and both do the same thing, think i'll get that old mallory rebuilt sooner. thank you for all the input.
 
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