by Drew Peacock Mon Oct 08, 2012 7:23 amI have been fooling arounf with my Holley 1940 carb on my van each time i drive it. Its an original ow mileage van which came to me with 1800 mile and i have since put another 800 on it. I can get it to where it starts and idles fine but once warmed up and the choke butterfly completely opens, the van will shake violently and almost die when coming to a stop. If i pull over and move the choke butterfly with my hands back to a position that is half way opened, i can get it to idle a bit better but not dead smooth but enough to where i can come to stops with teh van just slightly shaking. Its a 170 engine with a Holley 1940 model single barrel carb. The van came from Portland OR to NJ so the sea levels are the same. At this point, could timing be an issue? Could the timing be off such that after start it is fine but after driving and the engine is fully warm and the choke is fully open the timing is affecting the performance?
3 posters
More carb questions relating to choke
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
donivan65- Governor
- Number of posts : 12246
Location : San Diego, California
Registration date : 2008-05-12
Take some carburetor cleaner and spray it down into the carb after the engine is warmed up and when it acts up,,,,IF,,,the engine runs better, then you don't have enough gas or have too much air in that carb for the engine to run right,,,,, spraying some cleaner in it should kill the engine,,,,so run that test,,,,then we can talk about some next tests to run depending on how this test turns out.....
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
I'll try that tonight as I have to run some errands (get a timing light and vacuum gauge). I should mention that I received the van when it had 1800 original miles on it and it came with the replacement holley carb that had been rebuilt twice before. I never asked why the original autolite 1100 wasnt on it and what a carb rebuild was required twice on a low mileage vehicle.
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
it appears the carb may be wrong for my van - http://tffn.net/phpBB3/viewtopic.php?f=58&t=29544
donivan65- Governor
- Number of posts : 12246
Location : San Diego, California
Registration date : 2008-05-12
Those would be other problems, like loading up and flooding out or the loadamatic distributor not liking that carburetor,,,,,,but you need to run the lean test 1st, then move on to other tests,,,,
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
i sprayed the carb cleaner in the manifold and it killed the engine instantly - the carb doesnt have the spark advance piece on it that i believe is needed with a load-o-matic dist.
donivan65- Governor
- Number of posts : 12246
Location : San Diego, California
Registration date : 2008-05-12
A load o matic has no centrifugal advance weights in it and is real sensitive to what vacuum signal it needs so the carb has a spark control valve on it to control the signal,,,,,,,while a normal distributor has centrifugal weights and a vacuum advance unit on it and runs off whatever ported vacuum signal the carb sends,,,,,,there are some weird ones that run off manifold vacuum also,,,,,,you can disconnect and plug the vacuum line coming from the carb and see how the engine likes that for a test,,,,you could be running a mismatched distributor and carb set up,,,,,,the other thing is does it seem that there is a bunch of gas laying down in the carb when it acts up because it is flooding out?
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
my carb is missing the spark control valve - the holley 1940 carb DOES NOT have the base plate like an autolite 1100 would have that has a manifold vacuum port on it - essentially, there is an exhaust pipe from the exhaust manifold to the choke thermostat and a vacuum port on the carb going right to the dist.
donivan65- Governor
- Number of posts : 12246
Location : San Diego, California
Registration date : 2008-05-12
But do you have a load o matic distributor,,,,and is that vacuum port on the carb ported vacuum which is none at idle,,,,,,,I think people choose to get a normal or one of those electronic distributors rather than mess with spark valves and load o matic ones,,,,,just gather all your clues and put them together to see what you got and what choices of repair you have......
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
I have an autolite 1100 coming which has the spark valve. I bought the pertronix ignition stuff a little while back so i am going to install that this week as well. I would liek to think these two items together will aleviate my issues.
donivan65- Governor
- Number of posts : 12246
Location : San Diego, California
Registration date : 2008-05-12
Both of those will need the vacuum advance unit to be working correctly for them to work so everything works together,,,,,,,
dan nachel- Number of posts : 394
Location : sc
Registration date : 2012-01-24
You can check the vacuum canister by sucking on the hose and looking to see if the points move. My truck had the duel vacuum distributor when I got it, and that is a real pain in the but. I bought an electronic dist. with the wiring harness, coil, and brain box from the junk yard for $75.00. Well worth it in my opinion. Truck runs much better.
Drew Peacock- Number of posts : 63
Location : Jersey
Registration date : 2012-08-21
Good point Dan. I will be starting the pertronix conversion tonight and that easy little test will be at teh top of the list. Thank you
