The Stovebolt Site Forums The Shop Area Engine Shop runs rougher after warm up 1959 235

just tuning the 235 1959 after cheapo rebuild
new rings hand seat valves. the bore had checked out good. anyway when first start up before it warms up it runs great idles good. after warms up a little it wont idle at original setting and runs rougher. i am running without thermostat so not warming up to much.
any ideas ?? thanks

Hy rwb, firstly why no thermostat, the thermostat helps to bring the engine up to operating temperature quickly and helps to preserve the oil and prevent excess wear. I assume when you first start it there is some choke involved, does it start to run roughly once the choke is all the way off?

i was running without thermo just to eliminate making
sure wasnt going to heat up for check out.it runs really
good idles ect until gets a little warm then wont idle.
if i leave it alone start later same thing runs good at start up for about 5 mimutes drive a lttle runs bad.
i am running gas straight out of bottle container.
new coil and condensor.thanks

Hy rwb, before the rebuild how did the engine run?

it wasnt running sitting in a field at least 20 years
rings all carboned up.

Hy rwb, seeing as how we have no clue how the engine ran I would say a complete check and repair of all components is in order, carburetor, distributor, spark plugs, spark plug wires. If you could put a vacuum gauge on the engine and record and describe the readings for us we may be able to offer suggestions. My first thought is carburetor issues or a vacuum leak, hope that helps.

Reset the valves when the engine heats up,maybe they are set to tight.I set them with an extra 2 thou. when I first start an engine just to make sure it will run OK.After I get the timing set and the carb adjusted I'll go back and reset the valves when the engine is at temp.Get that thermostat in so you can get to operating temp.


Pete

i had the exact same issue after i rebuilt my 56 235

engine started REALLY easy without choke when cold and ran fine but once warmed up it would stall on idle (but ran fine otherwise)

i fixed it. the solution was either the fitting of a new coil (old one caught fire) or tuning of the carb idle valve. my money is on the carb tuning but cant say for sure as i changed both simultaneously

i tuned the carb by buying a cheap tachometer and using that to monitor the rpm wile adjusting the idle screw together with the idle fuel adjuster, engine warm. i managed to set the idle at the correct value circa 500rpm with the idle fuel valve adjusted so that any tigher drops the rpm and any losser has no effect. in other words i minimised the idle fuel metering to match idle fuel needs (at 500 rpm)

it solved the problem so my best guess is i had too much fuel at idle which was good when cold with no choke but bad when warm.

i think the idle fuel valve and idle speed needs to be set on a warm engine - when cold you use the choke to adjust. in my case the engine was set so it could run fine cold without choke...which was fine until it was hot then stall on idle

ymmv