1600 stock twin port - Hot engine question

[Karl1971]

Following about 500 miles of happy motoring since a good overhaul program back in the Spring I have developed something that seems to only happen when my stock twin port 1600 engine is hot...stalling when approaching roundabouts/junctions. This only seems to happen minutes after making a serious climb or two up some of the hills of north wales, so it's clear engine and oil is hot. No warning lights come on, she just fades out on me. I'm not massively worried yet (unless someone tells me otherwise) as on all three occasions I've had enough rolling speed to simply restart and drive on and then as I've been lucky enough to be on a flat allowing the 40 mph or so airflow to cool the engine down. But it happened twice this weekend and once a couple of weeks ago and as I plan to go to the Lakes later and would rather canvass a few opinions first before embarking out on a big trip.

Everything seems to be in order / no leaks etc underneath or in engine bay, and all new hoses fitted/ filters etc this spring, and after about 10 miles or sufficient airflow coming into the bay, she seems to cool down and then doesn't misbehave anymore - seems to basically be protesting!

My question is - is this perfectly normal and should it be expected if it is getting hot, or is there something else I should investigate?
Any suggestions or advice gratefully appreciated.

Thanks in advance.

1971 LHD crossover bay

 

[Trikky2]

Sorry but the question is a bit vague since there are many possible causes.

Assuming the engine has been recently serviced and all the settings such as points, timing, clearances etc are correct and theres no air leaks on the carb/induction system and the vac advance is working/no air leaks, good plugs and leads etc. then its probably just a case of tweaking the mixture screw a little.

Also make sure the throttle stop screw on the throttle arm is only just touching the stop plate when hot. Its there to stop the throttle butterfly from sticking on the throat of the carb but should never be holding the throttle open a bit. All the air at tickover should only come through the air screw.

ps. its not normal - though not an uncommon fault.

 

[Karl1971]

will try tweaking the mixture screw a bit then. havent checked the throttle stop screw since this has happened but like you say ought to have a look at when hot - thanks for your tips to investigate - will let you know how I get on!
Cheers

 

[BJ1]

This a classic symptom of tight valve clearances. As the engine gets hot the valves are held off the seats so the engine stalls at idle, but still produces power above 1500 rpm, when the valve clearances no longer matter. So get under there with the engine stone cold and check them. If they are tight and you keep driving you will definitely burn out the valves and seats and risk a dropped valve.

 

[Karl1971]

thanks for more sound advice...all sounds good will check tolerances again at weekend. cheers again

 

[bigdaz]

how hot is the engine when this happens? can you hold the dipstick without burning your fingers? if its really hot it could be due to Weak mixture Advanced timing, air leaks and many other things.
it shouldnt really be getting that hot. even on long climbs in the hot trmperatures in the south of France my van never really got that hot.
if its not overheating you could have an intermittent fault in an electronic component especially if they are Brazillian or Mexican.
The carb shut off valve might be breaking down when it gets hot. also the condensers can be tempermental.