cliff.b

Yes, despite not getting very warm my Spit was running beautifully on Sunday in the cold 5C air. Certainly seemed to be pulling well.

Yes, when I got the car the sender was faulty and the one I replaced it with, although sold as the correct part, read high. I then sourced another one which usually shows just under 1/2 and which I validated as correct with a thermometer, as described in the other post I have just made. It's only differences to usual readings that matter, I suppose.

Last summer I ran it on the drive with the rad cap off and digital thermometer poked in there. As it warmed up I saw the coolant flow increase when the thermostat opened and at that point, the thermometer read 84C and the temp gauge in the dash read midway between 1/4 & 1/2. When I next take her out it will probably be warmer do I will see what happens & investigate further if anything seems abnormal.

Well the gauge was reading just over 1/4 yesterday but the heater was hot. Am I correct in thinking you still get flow to the heater before the thermostat opens?

Fan not viscous, and also I think it might have an older style pump. It needs maximum adjustment to stop the fan belt slipping which I think is due to the pump pulley being smaller. Which would make the pump and fan turn faster, I suppose. Maybe this is a contributory factor 🤔 Anyway, I don't intend to make a habit of driving around in these temperatures regularly so it is more a matter of interest than an issue to sort out lol

I've got an 82C thermostat fitted and I think a 1500 Spit is supposed to be 88C, but assumed that was to let it run hotter for emission control purposes.

Yes, I suspect the thermostat was barely opening which will restrict the flow so the coolant will take longer to pass through the rad and return to the engine even colder, keeping the engine cooler etc etc lol

I have carried out some rudimentary calibration of my gauge in the past and based on that, I would say my car was also reporting mid to high 70C and the rad felt a lot cooler than that. But I don't plan to go out in those sorts of temperatures on a regular basis. I even felt the need to keep the hood up 😱

Took my Spitfire out for the first time in a few weeks yesterday, intending to give it a thorough warm up. However, even after 25 miles, some of which was at speed up the A1, the temp gauge barely went above the 1/4 mark. And when I got home the rad wasn't very hot at all. So I suppose since last Winter I cleaned out all the partially blocked water galleries in the head when changing the gasket, flushed the rad which happens to be a full width one, raised the bonnet about 5mm as it was hitting the bumper when opening, but that will have made the above bumper gap slightly bigger, fitted a smaller number plate as only 6 digits and it sits right in the airflow. Anyway, after all this it never ran hotter than 1/2 on the gauge, even in nearly 40C temperatures, but yesterday being only 5C and the heater on appears to now make it "overcooled". Maybe I should block some of the rad off if I go out when it's that cold again 🤔

As far as I am aware it is the springs that can be changed, not the weights and also the stop that limits maximum advance could be modified. Moss were selling a pack of various springs a couple of years ago and may still do so.

If it does make a difference I suspect it is only when "cruising" at moderate speed. Prior to my recent problems I unusually used almost an entire tank in a day driving mostly in the 55 to 65mph range with as little throttle as possible and covered 225 miles on the tank. Worked out about 35mpg which is better than usual and I think not too bad for a non overdrive car. Will be interesting to see if that improves now I have spent some time setting the car up, although I rarely get to go through an entire tank without some (ok, more than some) "enthusiastic driving" lol

That's exactly what I was experiencing I suppose when the original fault I described was occurring. And as the jet tube on the rear carb had worked loose and risen, it made that carb run very weak. Before I found the cause I put my Colourtune on no4 and could see the actual spark and just a very slight flame which confused me at the time but made sense in the end.

Yes, now I know what to look for I will check it all out at some point 👍

Yes, which ties in with the other things discussed. Probably need to look at the carbs in detail at some point and see what is actually in them.

I can set the mixture ok at tickover but find if I then stop at a layby during a journey and check the plugs they usually look light greyish or even white if I have been driving fast. Other people have said similar here. I usually then richen a little thinking it is better to be rich at low speed than weak at high speed. Was wondering if this is indeed normal or if perhaps could be due to worn jets or something. It's not a problem, but I assumed the mixture should stay roughly right throughout the rev range once set.

Yes, I suppose so. As a matter of interest, what would be the symptoms of a worn jet orifice? I'm assuming not maintaining correct mixture through the rev range but would it make it too weak or too rich at higher revs?

It's not bent, it's just that the jet pipe came loose. Maybe I have fixed it and it will be fine. If I do need to replace it though a new Waxstat jet would be easier and presumably certain to work ok. Are all the problems with them just because they are old or did they always cause issues?

Ah, it actually says it in the link you posted

I got the factory spare information from a table at thriumphspitfire.com Also saw it somewhere else that I can't remember. Maybe they were spare blocks 🤔

Just checked and my commission number is well in the middle of other 78 cars so that would be right. The engine number has a prefix of DM and a suffix of ESS which I believe means it was a factory exchange unit.

Is there a better solution, other than replacement Waxstat jets?

Ok, spanners out, air box off and another go at it all. Looked at the rear carb and the jet was above the bridge again by a couple of mm. I was at a loss to understand how this could be but took the jet out, measured it and it was longer than it was yesterday lol. Pulled the jet tube gently and it came away from the rest of the jet, which explains everything. Reseated it, squeezed gently in a vice and now jet is 4mm shorter. Feels tight so refitted, adjusted and then went through all the idle/fast idle/choke adjustments, some of which were way out. By eye, the pistons in each carb appear to rise together now, the tickover is perfect and running well on the road. Maybe it's time to bin these old waxstat jets and get some new replacements. Incidentally, the tag on the carb says FZX1258 so if what I have read is correct, either the carbs or the entire engine would appear to be from an earlier car. Unless mine was made in 77 and hung around for a while before being registered.

That's interesting. I will dig it out and have a read. I noticed yesterday when adjusting with the filters removed, although I got both pistons to start rising simultaneously, one then moved more slowly than the other. Need to check again that there is no binding or suppose it could be due to an air leak 🤔 Was initially wondering if due to differences between the carbs but that is probably a long shot. Work checking out now I have a better idea what to look for though.

Looking at what is available to buy online, both types say they are Red and 4.5oz but the earlier ones are long and thin and the later ones are half the length but much fatter. Not sure what, if any, affect that has on how they perform.

Any idea if the springs have any identification marks on them? The comments I read about the different needles in later Spits also said the springs were different. Looking at my carbs, there are some slight differences and I'm not 100% convinced I have a matching pair.