Technical Odd over heating situation

hey guys,

I'm trouble shooting something today and thought id throw it past you all. It's not really showing up in any searches so I don't feel this should be redundant.

Anyways my 46 ford has got this quirk where it's over heating at stop lights or stop signs of I sit there long enough.

It runs right where it should temp wise when driving in town or the highway but when I pull to a stop after about 30 seconds I can hear a subtle, we'll miss for lack of words. Just a soft drop in the idle every here and there. Nothing rythmic.

The longer I sit the hotter it gets and the more pronounced the miss type sound gets.

I could be at 160 deg and sit at a long light and come out of it at 200.

The only thing that seems to slow it down or prevent it is if I give it some gas and bring up the revs while stopped.

It doesn't seem effected by temp of the car or outdoors. It acts the exact same way consistently. It's pretty much always done this and I'm just now annoyed enough to address it.

This morning for shits and grins I decided to start it in the driveway and let it idle for a while and see what it would do.

With it sitting at high idle - which isn't all that high just a normal fast idle- it got to the normal operating temp of around 175 and stayed there for 45 minutes. This is in my driveway with a shut garage door in front of it. So no big wind or a fan or anything. The last 15 minutes it crept up to 190 ish.

It never made the slight miss sound, never over heated.

So my thought right now is in the ignition, more specifically the advance? I'm very green when it comes to distributors but I figure if it's only doing it under load of being in gear st the stop light but not at all when it park that that may be something to look at.

It's an hei with new coil, spring, button, cap and wires. The vacuum advance is a new rubber hose run to the correct spot on the manifold <edited> and is not worn, pinched or doing anything else weird. Trans shifts fine.

~sbc, th350 trans, not sure what else would be pertinent. Pulls something like 21 pounds of vacuum at idle has good oil pressure and never acts odd at all outside of this particular setting.

Ideas? Trouble shooting advice?

 

Original radiator or aftermarket?
Electric fan or mechanical ? HRP

 

I will add that it does this weather the long stop light is 5 blocks in to my drive or I'm just pulling off the interstate after 100 miles. The only time it's done it faster than another was in gridlock in 114 deg temps. And even then it wasn't that much quicker.

I also feel like it's done this the entire time the car has been together, before and after putting the new coil/ cap etc on.

Only other thought is it being related to a possibly flat cam. It's always been pretty low on power and I'm curious if the previous owner didn't break the cam incorrectly or if it's a bad factory cam.

Probably not related but worth mentioning as I've seen a lot of weird stuff acredited to a flatcam

 

Aluminum aftermarket radiator, brand new short water pump, mechanical fan.

 

I do believe that the vacuum advance should be hooked up to the carb, not the trans.
Pat

 

A picture of your fan and shroud might be helpful, but it sounds to me like that's your area of problem?

 

You might not have a problem at all. What I've learned about car cooling, in the last five or six years, is that 190-200 really isn't as bad as it sounds. My T Bucket used to climb to 205 in traffic and I would begin to worry, but it NEVER boiled over. It took me a long time to trust my radiator and coolant to do their job.

I don't think your miss is related to your coolant temps.

 

Is it a flex fan or steel fan,the reason I ask is I was having basically the same problem,I solved it by tossing the cheap flex fan and using a large 17" steel fan.

My problem was solved. HRP

 

How much initial advance? Was it set with the vacuum advance disconnected? Have you verified with a timing light that the vacuum advance is working?

Gonna assume its a misprint where you say the vacuum canister hose is connected to the transmission?

 

There you go.

 

Remember the cooling rule of thumb. Runs hot at low speed - not enough fan. Rus hot at highway speed - not enough radiator. The steel fan HRP is running should do the job.

Gary

 

Double check your "Initial" timing w/o the vacuum advance, then the amount of distributor advance.
Then hookup the vacuum advance and check too see what it is now.
We have found allot of distributors are advancing way to much.
Also, the vacuum advance should be attached to a "ported" vacuum source.

You may want to take a look at the spark plugs and see what color they are burning at.

What carb is one it Tim?

 

Remember 3 degrees F. per psi on your cap. So lets say a 15 psi cap raises the boiling point 45 degrees F. So I would not think 200F is too much to get excited about. My daily driver runs between 195 and 205 with no issues. Do you have a shroud in place?

 

Yes it's a misprint on the vacuum line from the trans. Brain fart on my part.

*its a flex fan, one of the Kevlar- i think?- ones

*its an edelbrock 500 manual choke

*vacuum advance to the the correct manifold port

*parked while running, driving 20 or 100 is runs about 180. It only over heats while in gear and stopped

*i agree it running at 200 would be fine if it wasn't puking. This isnt doing that. This is running 180, hitting traffic gridlock running past 220 and puking a liter. There's something wrong

*the face of the fan is about 1/4 to 1/2 inch from the radiator and is not running a shroud. I put one on, one of the stainless boxes that covers the entire back of the radiator and you cut your hole in it and it ran 20 ish degrees hotter on the highway and about 10 on the street but didn't change my stop light issue at all so I took it off.

It's really only doing it in gear stopped. The rest of the time it's fine, but if a train closes the road you may as well pull over and shut the car off.

I have not checked with a timing light to see that it's actually advancing. I was curious if it wasn't because I hear of flatheads getting warm because the advance isn't working. I was at loss however on how to test to see if it's working or not.

Don't get time to mess with the car every day but when I next get a chance that's the lead I think I'll follow up first

 

The reason I don't feel like it's a fan/rad issue on top of it being fine in every other situation is that if I were to slip the car into nuetral or park at the long stop it won't make the miss noise or get any warmer.

 

Is your trans cooler in the bottom of the radiator? If so disconnect it and run a separate cooler for it. If you take the trans load off the radiator I bet it will not overheat at stop lights.

 

It sure is! And that's a pretty valid idea as well

 

And is the mechanical fan close enough to the radiator with a shroud?. Maybe put electric fan on and put a over ride switch with it. Im guessing run both electric and mechanical. electric as a pusher on the outside of radiator.

 

you haven't mentioned a Thermostat. Do you have one? What rating? A 190f in fairly usual.

 

I think you are on the right path here... I was gonna be a wise ass and say the Ford is rejecting the GM trans mission transplant. In the mean time putting in neutral at stops is gonna save you until you get a separate trans cooler.

 

The fan is as close to the rad as you can get it.

On a thought about the trans cooler, while that makes since because it's obviously a source of heat I wouldn't think it would cause a funny miss sound when heating the engine up. That's what's pushing me back to ignition.

 

Thermostat is either a 160 or a 180. I changed it a year or two ago from one to the other to see if it made any difference.

It didn't.

I did test both before putting them in the car though

 

There is a clue in this quote for you.......
slipping it in to neutral keeps the RPM up and keeps the Vacuum advance "Happy"
Put in gear (tight convertor) drop 200 RPM and Boom! Vacuum advance is no longer "Happy"
Retarded Timing will build heat very quickly, I hope you are on Manifold Vacuum and not ported Vacuum.
I think you have an easy fix here.

 

Tim, In the history of cooling issues, a radiators transmission cooler has never been the source of overheating. Don't waste your time and money on chasing something that won't fix a thing.
A properly designed system with transmission cooling has absolutely no effect on the systems over all efficiency. Pusher fans are worthless I wouldn't use one. They restrict airflow. Ditch the flex fan and get a steel fan.

Gary

 

I wonder if the fuel in the carb is getting to hot. Try putting a spacer under the carb.

 

I think fed man has it. It would explain why when I bring the rpm's up at a stop light it doesn't happen.

 

Advance the timing a bunch and see what happens. I'll bet you'll have more power too. These modern fuels are crap and require a ton of advance.

 

Pull a spark plug from cylinder 7 or 8. Take a picture of the ceramic insulator that is inside the combustion chamber. Post it, so we can have a look-see.

 

Does that "slight miss" sound like a muffled thump in the exhaust?

 

As 54 Chevy said, "fuel in the carb is getting to hot". Had it happen to me, also what is the fuel pressure? maybe your carb is loading up and flooding..