Hi Everyone,

Hope you're all doing well! I've been battling what I'm confident is a temperature issue for the past few weeks and wanted to see if anyone here could weigh in/assist. Apologies in advance for the novel below.

I have a 1972/73 Fiat 500 F/R (We're currently having an identity crisis) that came with what appears to be a fairly modified powertrain when purchased. I've attached an image of the engine bay for everyone's convenience.

Last year I had the original (to me) Dual Spark ignition system, and I took about a 150km ( 75km each way) road trip with my 500 with an average speed of about 80km/h. I didn't notice any issues on the way there, but on the way back I had issues with the engine whereas it was surging while at speed (approx 80km/h) and the engine wanted to stall when coming to a stop at stoplights/stop signs, etc. As the car was fairly new to me and I was planning to replace the ignition system anyways, I went ahead and ordered a 123 Ignition Distributor, New Coil, New Spark Plugs and Wires and installed everything. I took a a few short trips (approx 10-15km) and everything seemed great, but as winter was coming, that was it until this spring.

Last week was the first time on the road in months, and I noticed that after about a 10-15km drive, I was running into the issue where coming to a stop at a light/sign, the engine would want to stall, and if i didn't tap the accelerator it would die. I did notice that the engine bay door was hot (really hot!) to the touch, and the engine bay itself was like an oven. I thought the main culprit was the exhaust, and I had previously purchased DEI Titanium Exhaust wrap, so I figured why not and wrapped the exhaust. On a small trip today, I went about 30km (mixed speeds, between 80km/h and lower) one way and everything was fine until probably the last few minutes, where the stalling issue reared it's ugly head again. At this point I noted that the engine bay was nowhere near as hot as before. I let the car cool for about 30 minutes while I ran errands, and when I fired it back up, it ran beautifully. On my 30km trip back, about 15km in, I started experiencing the same issue again. Once I parked the car, I noticed the intake manifold was incredibly hot, as well as the surrounding tinware, and the distributor.

I strongly suspect the temperature that the intake manifold is getting too is leading to fuel vapourization, however at the point, any help/advice would be greatly appreciated. The engine doesn't appear to have a thermostat, so I can't leave that open to cool it. All tinware is intact, and fan appears to blow strongly, but it gets hot in there. If my theory is correct, what are some effective ways to keep everything cool? I know propping the engine bay compartment open is fairly popular.

Thanks in Advance!


Edit: Just a quick note, this is currently my ignition coil . From forum research, it appears I should be using a Bosch Blue coil with my 123 Ignition System which is currently en-route from Pelican Parts. I doubt this is the fix to my problem (would be nice!), though I'm going to take a short trip tomorrow and see what temperature my current coil gets too, however this will be resolved in 1-3 business days if FedEx is to believed.

Have you checked your valve clearance?
These engines have a habit of the gaps tightening up when the engines are hot.
This can cause the engine to try and stall.

You say that you have no thermostat---does that mean that the thermostat flap is permanently open or shut? If it is shut, your problem might be a heat build up in the engine--does it make any difference if the heater flap (in the car, behind the seats) is open or shut? If the flap is permanently open, there might be a lot of very hot air constantly blowing over the distributor. I have no experience with the '123' ignition system, but I do know (from personal experience) that the 'hall effect' electronic ignition systems (the 'simple' electronic ignition sysytems) can be badly effected by the hot air being constantly blowing over the distributor---they fail in a spectacular manner!

Hi Franko and Hobbler,

I have not yet checked valve clearances. As this engine is somewhat modified, i'm not sure what my valve clearances actually should be, should I be going by the official clearances in the Service Manual?

Regarding the thermostat, I think I misspoke. I don't have the output flap that allows heat to run into the cabin, that's sealed up on my engine, but I do have hot air blowing out on the right-hand side of the engine as the attached image shows. Now whether that air is existing the outlet immediately upon the engine turning firing vs upon warming up is a great question, i'll have to test that today. A spectacular failure is definitely not something I would like to experience, especially as that 123 ignition system was not cheap!

Looks like you have a Panda 30 head there and modified cooling tinware. If you have cooling air leaks on the spark plug side of cylinder head either from ill fitting tinware or no seals around the spark plugs it will not help with cooling and help to heat up that big carb & manifold.

Hi Toshi,

Thanks for the reply, identifying the manifold alone was very helpful! The tinware appears to fit together well, but there are no seals on the spark plug holes. I had order a cable grommet kit a while ago, and 2 of the grommets are big enough to seal the spark plugs, while not a perfect fit, it's pretty good. I'm going to test that out now, and look towards a better seal.

Thanks,
Vince

I suspect it will be the thermostat and flap. i had exactly this issue. new thermo installed and job done. the cooling flap was not fully opening.

Rob

So I had a look between the tinware and the distibutor, and attached is what I found. Should the thermostat live in it's own enclosure that seals up that area?

I had the exact same issue and I believe for me it was the new coil I recently added to my new 650cc (converted from 500cc) engine. The thermostat and flap have been removed from my engine as well to allow for the larger muffler. The coil was getting so hot. I pointed an electric leaf blower to the coil and it started up after a few minutes of this cooler air being applied. So I changed the coil to an old larger diameter one I had sitting around and I think that solved the issue. I also inverted the heat shield to protect the coil from direct heat. Not sure if one or both of the changes I made is the reason but so far so good.
See my thread here...https://www.fiatforum.com/500-classic/480737-heat-issue.html

I've actually been following your thread for the past few days as it all seemed so familiar! Sealing the gap between the spark plugs seems to have helped a bit, though right now as I'm using rubber grommets that aren't an exact fit, i've noticed that they essentially ride up the spark plug wires which lessen the seal even more. I'll need to figure out a more permanent solution.

After a fun drive today, I did confirm that the coil is hot to the touch, not burn your hand hot, but difficult to hold hot. The bracket that holds the coil in place was burn your hand hot though.

Labman, do you have a photo of heat shield you mentioned? My coil is just exposed and I was thinking earlier of fabricating something to protect both the distributor and coil from direct heat.

Various suppliers can supply the correct spark-plug 'grommets'. They tuck in under the heat shield, so cannot ride up the plug. My advise would be to obtain the correct shrouding for the distributor side of the engine, complete with thermostat, and re-instate the heat-control flap in the back of the cabin. Looking at the pictures of your engine, I have never seen a right-side shroud that shape before! With everything correct, you might find that your heat problem is not as bad as it has been.

The correct grommets have been ordered, and with any luck they'll arrive that the same time as my new coil!

I'll have to go looking for the shrouding, though i'm not sure it'll even fit correctly, and unfortunately there aren't many local places here that would even know what this car is. This may be have to be an online shopping experiment. In the meantime, I might try my hand at fabricating some to redirect the airflow a bit more sharply downwards so it bypasses the distributor and coil entirely until I can confirm if the OEM parts will work.

Bambino, I think you're probably correct! I'm hoping that with the correct coil, spark plug grommets, and appropriate tinware that these overheating issues will be a thing of the past! I'll keep you all posted.

One last quick question, as Toshi pointed out, it looks like I have a Panda 30 head, and the stamping on my engine indicates this is a 650 engine. I'm assuming I have the stock camshaft, and if this were the case, what valve clearances should I be using?

It sounds to me as it your coil is working harder than it should and building up heat. Check all leads plug extenders and wiring with a meter set on ohms to see if you get a high resistance somewhere .

I'll test the plug wires this afternoon for good measure, though they're practically brand new so I hope there's no issue there. Thankfully no extenders on this setup, so there's that much less to worry about!

The tinware to fit a Panda 30 cylinder head is very rare and because the head is the same square cornered shape as the single port German 126 Bambino head the tinware fits. I would say that you had zero chance of finding a supplier where you are. Panda 30 cars and engines are even rarer. To my knowledge only a couple have ever turned up in the UK and I have never seen one in the flesh. The grommets are fiddley to fit on a normal engine so with your carb set up you will have fun.
As for valve clearance in the absence of camshaft info I would allow an extra thou or two to be on the safe side.

look at the "bargains" seaction of the "Van de Laan Fiat 500" web-site---they have the shrouding that you require, complete with thermostat, for sale. It is 2nd hand, but if given a good clean and a paint, with a new thermostat fitted it will do the job for you.

Thanks for the info Toshi! It'd definitely been a learning experience trying to figure out what I have with this car. The chassis in theory is a 1973 500R with a 595 engine, though registration says 1972. Fiat 500F Door Cards fit, and 500R don't. Transmission is fully syncromesh. The engine stamping indicates a 650, and the head was unknown to me until you pointed it out. It's been interesting!

Luckily there's an old school Fiat mechanic about 70km away from me that I'm planning to visit for a some odds and ends in the coming weeks, if he doesn't have any sort of compatible tinware, then i think you're pretty close with my chances being at 0.

The extra thou or two would be based on the stock recommendations for 650 engine correct (0.20 mm for inlet and 0.25 mm exhaust)?

Thanks again!

hobbler thanks a million! In theory then I would remove my existing shrouding on the right-hand side, and then just fit this, and reconnect my cabin heat? It sounds way too easy. As this car is really only driven in the summer here in Canada, would it even be worth setting up the thermostat?

ilgrilleto said:

I've actually been following your thread for the past few days as it all seemed so familiar! Sealing the gap between the spark plugs seems to have helped a bit, though right now as I'm using rubber grommets that aren't an exact fit, i've noticed that they essentially ride up the spark plug wires which lessen the seal even more. I'll need to figure out a more permanent solution.



After a fun drive today, I did confirm that the coil is hot to the touch, not burn your hand hot, but difficult to hold hot. The bracket that holds the coil in place was burn your hand hot though.



Labman, do you have a photo of heat shield you mentioned? My coil is just exposed and I was thinking earlier of fabricating something to protect both the distributor and coil from direct heat.

Click to expand...

Here is what I did. Due to the larger muffler and tubes, I could no longer use the OEM heat shield. So I inverted it and added two brackets I made to hold it in place from the existing screw holes. As you can see it doesn’t cover the entire coil, but covers the part closest to the exhaust tube diverting a lot of the heat away from the coil. I may install a heat blanket for the exposed portion but so far I don’t need it.

Interesting, that looks pretty straightforward, and the heatshield is pretty inexpensive online. My new coil and grommets allegedly arrive tomorrow, so i'll try that out first, and if i'm still running into issue I may just copy what you've done there. Thanks for the photos!