Overheating, need help

[mburger]

I’m sticking with the plow theory. The entire system works as designed and expected until the car is moving at speed. For some reason, air flow through the radiator is being restricted at highway speeds whether by vacuum or other means.

[Brastic]

We had a car do this once. It would be fine at start up and below 25 MPH. Anything above that and it would over heat. After months, we found out that the plastic impeller water pump was the issue. We installed a metal impeller water pump and the issue went away. The next month a friend came over with the same issue. We did the same cure. That was in the 90s, so maybe the plastic they use now days is better. I will never know.

[cob427sc]

Thought I'd just follow up now that the overheating problem is solved (I believe). As I mentioned I back flushed the block as best as possible along with the radiator and had all kinds of black debris come out. I had the radiator back flushed and flow checked by a radiator shop and checked out fine. I built an aluminum fan shroud and reinstalled everything. Currently with a 160 t-stat, the temp gauge reads 190 when it opens and the fan comes on at 200. On the highway where I had my problems, the gauge rises to 210 and never goes higher tested today in almost 90 degree weather. The overflow never received any water, not even a burp. All in all it seems to have cured the issue although I suspect that the temp gauge ( FFR cluster ) is not accurate and I may do some more research. Now all I have to do is stop the slow leak on the rear main seal that I've been told is normal for these engines. They even put a drip hole in the bell housing cover to allow the oil out! Thanks everyone for the help and insight.

[NAZ]

Just thought I'd mention that t-stats start to open at the rated temp and may not be fully open until they reach 15-20 above the rated temp. https://www.stant.com/index.php/engl...s-thermostats/

[Fixit]

A buddy of mine is running practically the same setup in his steel '31. Next time I see him I'll take a closer look at his setup - he lives in the boonies and has to drive highway to get anywhere... never has an overheat problem.
9365_Nailhead.jpg

[FFinisher]

Sounds like you may have it, But you also want to check the cap. FFR supplies a 20LB cap, Do you have a significantly lower cap pressure? lower cap pressure = lower release pressure.

[cob427sc]

My cap, which came form FFR says 14# release. Might try a 20# see what happens. Thanks.

[NAZ]

Ditch the 14lb and install a 20lb. It will not keep the coolant cooler but will add a margin of safety against boil-over.

[JimLev]

A lower pressure cap will allow it to boil over sooner at a lower temp.
Mine came with a 16 Lb cap.

[wrp]

wrp, Simplification was a mantra. We ran Ford dual point distributors with mechanical advance only. We timed for no more than 36-37 degrees from 3500RPM-up, the rest took care of itself. I think we started the engine with about 10 degrees.
jim[/B]

Thanks, I guess this is where I was going, I will admit I spend a lot of time at 3500+ RPM, probably a good deal more than I need to on the street. If I drive like an average person is supposed to, I rarely get over 2000 RPM. That is especially true when I am cruising on a four lane highway. My SBC likes 12-14 degrees on starting. With the mechanical advance MSD setup I only had about 18 degrees of advance to play with. With the vacuum advance, I could back the timing down with a wider range of advance available but I still had issues because of the cam size and resulting weak vacuum. Without the computer controlled timing I had to set it around 18-20 degrees to get it to advance to 34 degrees at WOT. So when going through the gears from light to light I am likely to get over 3,000 rpm, cough cough, depending on the model 5.0 Mustang beside me. My Holley carburetor is trying to use the already weak vacuum to decide whether to be in the idle circuit, transition circuit, or the cruise circuit. With only the mechanical advance, the low speed performance resulted in a wide range of over fueling and under fueling (rich/lean). 2000 RPM seemed to keep me in the lean side of operations, read from my plugs. Some people are good enough to tune the carb and time the motor to meet specific driving conditions. I am not. Hence I noticed the operating temperature drop when going to the computer controlled timing EFI system. One thing I forgot to mention about is that I took the whole radiator down and had it pressure tested with the cap on and found I had a weak spring in the cap that came with the original kit. Changing that seemed to help too.

[NAZ]

Most folks know that we set the timing advance BTC because it takes time to burn the mixture and the AFR (lean or rich) will affect how far advanced we need to go. But not everyone knows what we're trying to achieve by starting the fuel burning before top dead center. So here's a couple of articles that help to explain what the goal is and how too much advance too soon can be a bad thing. If you search you'll find more out there but these two will get you started.

https://www.hotrod.com/articles/set-...l-performance/
https://innovatemotorsports.com/resources/myths.php

[J R Jones]

NAZ, I was at Mercury Marine when emission laws were applied to the marine industry. Merc was experimenting with four-stroke and clean two-stroke they called Optimax. It was licensed from Orbital in Australia. High pressure fuel and high pressure air. Anyway, to evaluate the combustion event we made clear acrylic plastic head/combustion chamber and took high speed film. We revved the engine to speed with a motor, introduced fuel, lights, camera, ignition. It was similar to a slow-mo movie explosion.

[NAZ]

NAZ, I was at Mercury Marine when emission laws were applied to the marine industry. Merc was experimenting with four-stroke and clean two-stroke they called Optimax. It was licensed from Orbital in Australia. High pressure fuel and high pressure air. Anyway, to evaluate the combustion event we made clear acrylic plastic head/combustion chamber and took high speed film. We revved the engine to speed with a motor, introduced fuel, lights, camera, ignition. It was similar to a slow-mo movie explosion.

That had to be interesting. You had the kind of jobs I should have had.

I've seen ones like these before: https://www.youtube.com/watch?v=jdW1t8r8qYc

[J R Jones]

NAZ,
Jezus, I managed a similar Briggs 12 engine development too. Took it from 5.5 to 7.5hp. It was an old cart/snowblower engine they made 3.3 million/yr.
GD spark plug and exhaust valve were so close I couldn't keep one of the head bolts tight. I put a heat sink under the bolt head and cooled her down. Too Expensive.
I had to go external with the oil drain-down with the enlarged bore. Not my favorite job.