weird problem

the van surges lightly at highway speed and then when i slow down for a light, the idle crashes to like 300rpm and then sometimes stalls the engine. its intermittent too, i have been messing with the timing and air/fuel mix trying to pinpoint this problem. it appears once the engine is hot. what do you guys think it could be??? the engine idles smoothly at rest but after i push it for a while on the highway it wont idle smoothly until i mess with the mixture screw again

Could be the carb just needs to be sorted out.
Hows the engine vacuum ?


mike

Fuel or fuel filter? Could even be bad gas or maybe fuel tank strainer. Dirty carb or just sucking air someplace....

carbs are such a prob mine bogs when i give it gas going around a turn. float adjustment good luck steve on your quest to solve the vintage lust to drive them

yeah its a weird one ... vacuum is solid, fuel filter brand new, compression is 21 in/hg at idle, oil 49psi at idle, i'm going to gap the plugs today which are all clean and not worn, carb is new (factory rebuild), pertronix ignition, i think it may be the plugs?? pulled over on the side of the road like ten times last night fighting to keep her going. this suddenly started after months of reliability.

Just to throw stuff out there:

I wonder if it might be a bad seal in the carb that acts up once it gets warmed up.

Does yours have a timing chain?

it could be the gas is getting to hot before it gets to the carb. How is your fuel line ran/ Does it go to the back of the doghouse and up the side over the exhaust? If so that is probably the problem. I had the same thing happen to me on a couple of Econos and that is what it was. the fuel line should go up from the pump and then straight to the carb without going up and down. Also a bad gas cap will cause the same problem you are having.

gapped the plugs which were out by only a couple thousands, cleaned them too. made a difference no more surging and idle problem cleared up. i drove to my mechanic buddys house and we put a light on her. turns out that the distributor was off by an entire gear tooth which is why the vacuum advance diaphragm needed to hit the block for the van to run. we moved the distributor position and power timed the van. after some mixture adjustments and idle setting we roaded her and whammy!! power galore! i even tailgated an f150 up the hill by my house at like 65 mph! (an inversion of the normal predator/prey relationship) i think that the issue may be addressed now, but we'll see. i have to pour some methyl hydrate in the tank as we found some water in the fuel filter when i changed it yesterday. it may have been barfing on some water, when the petroleum companies change to a summer blend for the season i heard it can make your vehicle go screwy for a week or two.

Great work, Steve! Must be a relief!