Just a quick question regarding thermostat temp choice. I am using a 74C but engine does not run smoothly, appears weak mixture. tempted to fit an 88C, for the winter. What thoughts.
Regards John
Mgb thermostat
Re: Mgb thermostat
What does the temperature gauge indicate? Do you have an oil cooler fitted?
I think an 88 would be a better bet.
Ian F
I think an 88 would be a better bet.
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, now sold
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, now sold
Re: Mgb thermostat
Hi Ian
Thanks for the reply. Actually I am trying to adjust the mixtures, but think that the 74c thermostat is not allowing the head to reach a good temperature to do this, especially in these low temps. I have richened the mixture by a flat, so tomorrow I will try the 88c. With the current 74c the temp gauge indicates about 160-165F, the oil cooler is still operational. This car, 1970 GT and is a daily runner.
Regards John
Thanks for the reply. Actually I am trying to adjust the mixtures, but think that the 74c thermostat is not allowing the head to reach a good temperature to do this, especially in these low temps. I have richened the mixture by a flat, so tomorrow I will try the 88c. With the current 74c the temp gauge indicates about 160-165F, the oil cooler is still operational. This car, 1970 GT and is a daily runner.
Regards John
Re: Mgb thermostat
Thanks John. I asked about the oil cooler because my 72 BGT is fitted with one and I suspect it really keeps the engine cool - perhaps too cool in Winter.
I would have thought that if the engine is too cool then it should improve with a little choke? Cold engines require more fuel.
You may find that after you fit the 88, the engine warms up properly and you don't need that extra enrichment on the SUs.
I always used to check the plugs regularly when setting engines up. Useful to do this after idling the engine, but most importantly after a longish burst of full throttle at high speed. This is when you really do not want the mixture to be too weak. I would switch off after a high speed run and coast into a safe spot for parking, and then check the plugs. If they were white then I would definitely enrich the mixture (different needles or carb adjustment).
Keep us updated!
Ian F
I would have thought that if the engine is too cool then it should improve with a little choke? Cold engines require more fuel.
You may find that after you fit the 88, the engine warms up properly and you don't need that extra enrichment on the SUs.
I always used to check the plugs regularly when setting engines up. Useful to do this after idling the engine, but most importantly after a longish burst of full throttle at high speed. This is when you really do not want the mixture to be too weak. I would switch off after a high speed run and coast into a safe spot for parking, and then check the plugs. If they were white then I would definitely enrich the mixture (different needles or carb adjustment).
Keep us updated!
Ian F
MGCC member
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, now sold
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, now sold
Re: Mgb thermostat
I've said this before, but in my humble opinion after 40 years of MGB experience, the oil cooler is entirely unnecessary in the UK climate unless you are going racing, or such like. At the very least I think you should cover the cooler with foil to prevent the cold air passing through it. On my 1800 roadster I fitted one of those oil temp thermostats in the cooler feed lines. Basically it stops the oil reaching the cooler until the stat measures an oil temp of about 85 C. Even on warm summer days I could get out after a run, open the bonnet and feel the cooler. It was almost always cold to the touch, showing that the stat had not opened.
But consider this - in the middle 1990s, MG Rover produced the RV8, basically an MGB shell with the 3.9 litre V8 under the bonnet. I have the same engine in my BGT conversion and I can assure you that it produces much more heat than the 4-pot 1800. Did MG Rover fit an oil cooler? No they didn't. I don't have one on my BGT V8 conversion and have no trouble with overheating or low oil pressure.
However, a 74 degree stat is too cold, again in my opinion. I would run an 88 all year. Running an engine too cold is very bad for it. You need the oil to get up to over 100 degrees C for best running and engine longevity. That's why the MGF / MGTF has an oil temp gauge, and why the handbook says not to stress the engine until the gauge reaches a normal temperature.
But consider this - in the middle 1990s, MG Rover produced the RV8, basically an MGB shell with the 3.9 litre V8 under the bonnet. I have the same engine in my BGT conversion and I can assure you that it produces much more heat than the 4-pot 1800. Did MG Rover fit an oil cooler? No they didn't. I don't have one on my BGT V8 conversion and have no trouble with overheating or low oil pressure.
However, a 74 degree stat is too cold, again in my opinion. I would run an 88 all year. Running an engine too cold is very bad for it. You need the oil to get up to over 100 degrees C for best running and engine longevity. That's why the MGF / MGTF has an oil temp gauge, and why the handbook says not to stress the engine until the gauge reaches a normal temperature.
Mike
1969 MGB GTV8 3.9 Conversion. Many classics have passed through my hands but the faithful BGT V8 is the last man standing.
1969 MGB GTV8 3.9 Conversion. Many classics have passed through my hands but the faithful BGT V8 is the last man standing.
Re: Mgb thermostat
Thank you all for your help.
I have fitted an 88C thermostat today, incidentally, the one I took out was actually an 82C. On the test run the 88 was much better, I will keep this in for the winter.
The oil cooler tip is good and I will be making a bespoke removable blanking plate.
Also I agree with Ian, that after the mixture has been adjusted, test runs are the best, and after each run a check should be made on the spark plug colour with minor tweaks to the mixture, half a flat at a time until their colour is a light brown.
Also just a tip regarding changing the thermostat. Draining the water from the radiator can be a bit of a pain, as most mgb radiators no longer have the fitment of a drain tap. So I use a turkey/chicken baster and take the water out of the filler cap, the top of the radiator core is just about level with the thermostat,
Thank you all regards John
I have fitted an 88C thermostat today, incidentally, the one I took out was actually an 82C. On the test run the 88 was much better, I will keep this in for the winter.
The oil cooler tip is good and I will be making a bespoke removable blanking plate.
Also I agree with Ian, that after the mixture has been adjusted, test runs are the best, and after each run a check should be made on the spark plug colour with minor tweaks to the mixture, half a flat at a time until their colour is a light brown.
Also just a tip regarding changing the thermostat. Draining the water from the radiator can be a bit of a pain, as most mgb radiators no longer have the fitment of a drain tap. So I use a turkey/chicken baster and take the water out of the filler cap, the top of the radiator core is just about level with the thermostat,
Thank you all regards John