That cooling issue again..

Timing was set to 32 at max advanced but then tweaked on a rolling road so not 100% sure where it ended up. I'm running twin ICT's so slightly different

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Thank you for a well informed reply, that makes a lot of sense and could be the reason. I have often sat with my foot on the throttle to increase the idle after a long run, just for a few mins, same idea as we used years ago on turbo engines just to let the circulating oil pick up residual heat and cool things down before switching off. That seemed to work.

The idea of individual heat tolerance crossed my mind but I had no other way to describe it .. Im sure this is an external fix.. either a switch, perhaps a faulty pressure relief valve, maybee timing,perhaps mixture ,

Im going to give the thermostat and associated parts a check, but I think thats going to be fine otherwise the motor would roast itself even on a cool air day.. Ive seen the brackets come loose and the thermostat pushing and pulling the bracket and not the actuating rod .. but Im sure thats not the cause here ...

If I have to take it out, its definately not going back in, that would be the excuse to fit the subaru thats on a pallet with the rest of the conversion kit at the back of the garage ..

 

My bad, webber ICTs are what I have .. keep calling them solexes for some reason.. mental block..

 

In that case this is what I have:
145 Main
F6 Emulsion
185 Air Correction
57 Idles


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30mpg is suspiciously good and might be an indication of a weak mixture and/or too far advanced ignition timing – but that would increase cylinder head temperature more than the oil temperature. And it could equally be the result of a very gently driven bus.

Without knowing the cylinder head temperature, oil pressure and oil temperature it’s going to be difficult to identify the problem, if there is a problem at all. Fit some gauges so you know what is going on, at least oil pressure and temperature.

Have you tried a different oil pressure switch?

Has there been any glitter in the oil? Incidentally, oil changes every 800 miles are very frequent – why?

It would be worth checking the smooth operation of the oil pressure relief valve but I doubt if there is a problem with it at such low miles.

 

Re the frequent oil changes, its just something Ive done since first start up.. Set off with running in oil, yep there was a bit of glitter in the beginning, but its been pretty clear for a good while now. I just stuck with the frequent oil changes to prolong the life of the motor .

Its always returned mad MPG figures .. Its the stock 60 litre tank Ive commented a few times that the gauge must be knackered given the miles covered but on fuel stops its always shown to be pretty accurate. I have wondered if I just got lucky.. It doesnt pink and it pulls strong and cleanly in top from below 30mph.. its mostly driven between the 48 to 55 mph range to be honest

Temps and pressures might be the next thing. There is no issue with it most of the time which is why I question it . Im guilty of driving it at 30 in top but it pulls clean. Most of the times ive noticed the flickering oil light ive just arrived home .. I have to negotiate a fairly steep hill into the village, the van will pull up it at 30 in 3rd easy. then its 100 mtrs down hill and a right turn and im home .. Its only ever when the weather is warm that I get this flickering..

Im going to go through the whole deal next week , starting with the thermostat bellows and mechanism, but sure ts OK as it generally keeps its cool ..

will check the valve clearances although again, If they were to tight or to slack I think they would show a weakness across the range of weather temperatures ..?

Will re check timing, its a while since its been done but it continues to run great so really I don't anticipate anything drastic. .. not to say its not to advanced ..

then will do the carbs if there is still a problem ..

If that's all good and it still flickers after that then fit a new switch and other warning devices ..

If I cant get to the bottom of it i'm just going to use it as an excuse to fit the subaru motor ..

 

i reckon it is running a bit lean,

 

I would also try a different brand of oil - I had a similar problem in my MG - oil pressure drop on the motorway after 60 mph for 1/2 hour (down from 60 to 25 lbs). I was using Halfords Classic 20/50, and decided to go to Valvoline Vr1 - the pressure holds up at over 40 lbs now.
It could also be your timing or mixture needs adjusting.

 

seems it not unique .. found this post on google search ..

Oh, and one more thing. There are a few things that can happen during the summer months that don't normally happen during the winter months: 1) If you're driving the highway and come to an idle, your oil light can flicker. This happens. Consider using a thicker oil. Many fight over oil viscosities-- but most choose the 30 wt or the 20w50. I use the latter. Oil thins out as it gets hot and your oil light flickering is symptomatic of that. Again, take it easy going down the road. 2) your car can vapor lock much easier during the summer months. This occurs often when you drive the highway, come to an idle, and the fuel pump gets so hot itself that the gas vaporizes on contact with it. The pump is designed to pump a liquid, not a gas, so it stops pumping fuel into your carb. Your car uses what gas it has in the carb bowl, and when it's exhausted, your car dies of gas starvation. Keep a bottle of water with you and when it dies, pour it slowly over the fuel pump. Then crank the motor (for awhile, as though you had run it out of gas and were trying to get gas to it for the first time-- maybe a min even), and it will run again. Motor on. The long term fix for this problem is to use an aftermarket electronic fuel pump and a block off plate. This works well to fix the issue.
Motor on this summer, but make sure you take care of your ride. Again, your car is likely 45 years old plus, and she's not a speed demon. A friend of mine once told me... "Drive her like an old lady and she'll stay with you forever. Drive her like a young lady, and she'll leave you." Seems appropriate.
** Two other notes on oil... I'd rather the thread below not just be some diatribe on what oil you use, that's not the intention of this post. Let's colllectively avoid that and understand that different people choose different viscosities.
Second.... Ben Gresham last summer was driving The Yellow Rose, his 74 Super and he was having trouble with his oil light coming on at idle after running at highway speeds. He was a user of Castrol 20w50 and switched to the "High Mileage" variety of that oil. I don't know whether it breaks down less slowly at high temps, or has a little extra umph, but it fixed his oil light problem. Not saying this is a remedy, but it worked for him. And he drives his car 65-70 on the hwy all year long.
Update: 4-17-2018.

 

im prone to agree. Its probably close as it runs ok and idles without s flickering oil light in cooler weather that slight temp increase from the lean mixture is probably exaggerated by the increased air temp which tips it over the edge .. thats my theory.. was kinda hoping it would be confirmed by someone whos had the same issue..

 

Mine has started doing this since I replaced a middle block that seized with another donated off here (thankyou) & rebuilt the engine. I've been told to fit a heftier oil pump??

 

Im sure ive read a post that says the VW manual states that the oil light may flicker occassionally if coming off a motorway etc, but it isn't a problem if it goes out when you rev the engine.

Has anyone got a manual to hand?

@redoxide does that sound like your situation?

 

You are paying for overdoing the fuel economy by frying the engine. and 32 degrees advance is the upper edge .
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If your engine is built with a large deck height and low compression then it will get hotter if run lean as the burn manages to hit the cylinder walls rather than completing while the piston is about TDC and the hot bit is kept in the combustion chamber by having a 1mm squish zone.

Adjust deck height, richen up the mixture and retard timing a bit should cool it down.

Or if you want to live on the edge at 30mpg, at least get an oil temperature gauge so you can back off as it gets hot.

You can help flickering symptoms as a stop gap by bumping up the idle speed.

I used to do do about 60-65 mph with a 1641 running at 120 deg C on the dipstick sender. It flickered the oil light at idle. It was knackered. Returned 19-21mpg.

So I full flowed it with a cooler in a scoop with an 80C thermostatic sandwich plate. And used a permanent AFR installation for setting up the jetting.
It is set to run quite rich at WOT.

Temperatures dropped 15 to 20 deg C.
But the hot flickering got worse over time . Eventually abandoned that engine after about 35k miles , built another without any line bore / regrind on an original case. Oil pressure was better on the new engine, but gradually declined. Dropped a valve before that one got too low, it died at 25k miles.

First engine had badly worn bearings and dowel pins in oval holes.

Bought a brand new engine last year. Idles at 25-30 psi /800 rpm, 45psi at 4000rpm and 100C oil temperature.
Returns 21-22mpg.

Fitted an oil pressure switch adaptor with a stock pressure switch after finding my electronic sender had a zero shift when the engine got hot. It showed a negative pressure once... the adaptor also cooled down the electronic sender so it stayed accurate.

I am still happy driving it at 68 GPS mph(indicated 73 mph)