Technical How to reduce under hood heat

Another question: Is the "too hot" condition worse while sitting still or on the highway? And if your concern is simply due to Vapor Lock or not......We haven't seen your thoughts on replacing that fan with one that will actually draw more air through the radiator and condenser.

 

Rock, modern cars are running at a lot higher temps then 205 -225 without issues. I am actually running 195 thermostats in all my Mopars, I know the temps are in to 200-220 range nearly all the time! I've certainly run enough miles in very warm outside temps that if the temp was a cause of vapor lock, I would have experienced it.

I think your vapor lock issue may have some other cause. I would follow your fuel line routing to be sure the lines do not run through an area where heat can build up.
Also, it may sound pretty dumb, but try running gas from a different station/brand then you are now and see if the vapor lock goes away. The menthol mix on some stations varies a lot, and that stuff doesn't like heat very well. Is it possible the gas you have in your tank is still a winter blend? It doesn't like heat very well either. Gene

 

This is a 40 , we ran a 4 core cross flow Mechanical fan, no Shroud for 30 years in va , Experimented with different pulley combinations solve the problem, with inner fenders. stock fire wall,
Maybe playing with timing.

 

Thanks guys. It has to get hot here before I can try to determine if a solution is effective and to what extent it is a problem. I will get to the bottom of it and I will do it one step at a time, probably using some of these suggestions. I don't control the weather, so give me a little time. I will report back. I see this as something we can all learn from.

 

I'm watching this. I have a nailhead in a Buick where a straight eight was originally. I can keep the engine cool enough, but heat in the cab is serious and always has been.When I was younger it was easier to cope. Now I'm considering those openings at the inner fender. Don't quite understand the deflectors hanging below, but I'm interested.

 

The significant problem these days, as mentioned above, is the FRIGGIN' Ethanol, however you spell it. It boils at a lower temperature than pure gasoline, and the winter blends are worse than summer blends. FI systems don't have the problem due to the high pressure fuel delivery systems. Back in the old days, vapor lock was a rather rare issue, but now, LOTS of guys with carbs have this issue... oh well....

If ya'll haven't checked my postings above, the thing I did was to keep the mechanical fuel pump, but added an electric with a check valve and a return line type GM fuel filter just before the Carb so when the electric is on, it flushes the whole system up to the carb with cool fuel. Put a push button switch under the dash to turn on the electric for about 30 seconds before startup in hot weather.... seems to work..

 

gasoline is a blend and generally has a BP in the mid 90's F at atmospheric pressure. Ethanol
on the other hand has a BP of 173*F

 

That brings up a question in my mind. Gasoline's boiling point is initially in the mid 90's, but it has a range from there up to just under 400 degrees. Does the ethanol/gasoline blend boil away easier than straight gasoline, or are we just chasing our tails on the boiling/evaporation issue?

 

It may have something to do with tuning.

Straight gasoline has a ideal stoichiometric air to fuel ratio of 14.7:1

E10 has an idea stoichiometric air to fuel ratio of 14.13:1.

If your fuel delivery device of choice has not been specifically tuned for E10, and that's what you are running through it, then it is not properly tuned.

Lean mixture fed engines run hotter. Lean mixtures also take more time to burn, so they require more spark advance.

If you have not also adjusted your advance, both initial, and total, that is likely wrong, too.

This ain't 1959, and there is no going back. Tune for the fuel you have.

 

nahh, you're cool -- they were invented in the 1920's. here's a 1942 Popular Science article...


https://books.google.com/books?id=X...Tgo#v=onepage&q=popular science cannon&f=true

 

205 is fine. That’s not even boiling point of water. With a good pressure cap on the radiator, and a 50/50 mix of antifreeze and water, you’re nowhere near overheating.

My Chevy runs about 220, always. Going down the highway at 80 MPH, or sitting in traffic.



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I'm sorry, I should have been more specific with my question. What I am wondering about, more than the tuning aspect, is the fuel disappearing/boiling away/evaporating from the float bowl, and how that might be affected by the ethanol, taking the boiling points of both into account.

 

While the initial boiling point of E10 is 5ºF lower than E0, the combination of ethanol and gasoline should have a higher overall boiling point than straight gasoline.

That said, neither is all that high, especially for the lighter components of gasoline. That is why I mentioned tuning.

An engine that is being fed a lean mixture will be running hotter than the proper mixture. That extra heat will not be doing good things for any combination of fuels. Timing that is late for that lean mixture just makes this worse.

I encourage anyone who suspects fuel boil-off from the float bowl to invest in a non-contact pyrometer (infrared thermometer). You can get one for about $20-25.

Point that at the base of the float bowl, right after shutting the engine off. That will tell the tale.

Gasoline begins to flash off at 95ºF. By 395ºF, it will no longer be any sort of liquid.

E10 begins to flash off at 80ºF. By 430ºF, it will no longer be any sort of liquid. Yes, you read that right, it is higher.*

Even if there was full ethanol flash-off, from E10 fuel, there still would be enough combustible fuel left behind for the engine to run. I suspect that some are experiencing carburetor temperatures that are high enough to flash off more than just the ethanol.

The coolant temperature is not always a good indicator. The temperature right at the carburetor is more critical in this context. Even if the cooling system is up to the task of taking the excess heat out of the areas serviced by the water jacket, the areas that are not serviced by a water jacket are subject to the havoc of heat.

E10 has a 5% lower flash off rate than straight gasoline.**

*http://www.lionoil.com/msds-files/e-10-blends.pdf
**https://www.tandfonline.com/doi/pdf/10.1080/10473289.1994.10467294

 

On mine, the inlet needle failed in the carb. On shut off of the engine, it would almost immediately empty the bowl. Some went down the intake, but not much. Most vaporized and vanished.



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I haven't seen it mentioned, but for the heat soak problem you might try a phenolic(sp?) or wood spacer under the carb. They do work in insulating the carb from engine heat.

 

This thread is wandering off topic. The topic is reducing heat under the hood, not preventing vapor lock. I already stated that I have an insulator and a wooden spacer under my carb and an electric fuel pump. (One of the side effects of this is harder than normal starting after it sits but that problem will rectify itself if I figure how to solve the primary problem.) The problem I'm trying to rectify is high temperatures under the hood and would like to be able to share this info for others.

We all know you can punch a bunch of holes in the hood and fenders and give the hot air an easy escape route. I'm not going to do this on this car. We all know that airflow across the radiator is important and I believe that is not my problem with the fan running. It does seem to be a problem without the fan running while at highway speeds, however. Right now, ram air is not getting the job done and it may never

I am going to try aerodynamic tweaks first before resorting to other means. I will report my findings when the temperatures warm up here, which shouldn't be long.

Thanks

 

Soooo. ...did I read that correctly? You don't have a vapor lock problem? But at highway speeds it gets "too hot"? No problems sitting in traffic at low engine rpm?

If what you just said is accurate then you're probably running lean and/or retarded.

On the other hand "hard to start after sitting" is classic vapor lock and has nothing to do with aerodynamics at highway speeds.

We have all been trying to help you out but I guess you've got it analyzed for yourself. Good luck.

 

At highway speeds, it seems to want to get hotter than I want. It will idle all day without getting too hot. I've richened the carb, increased the vacuum advance, etc. The tune up is good.

Thanks for your help and suggestions. The fan recommendation may yet have to be used but, so far, it seems the fan moves a lot of air.

 

Whenever I see threads talking about under hood temps and needing to get the air out of the engine compartment, as if that is a problem, I'm reminded of modern cars that are packed tight with components, and are sealed up tight to improve aerodynamics and maximize fuel efficiency, you couldn't design a more constricted air flow if you tried, and they don't have problems with running too hot. I'm a skeptic that this is a problem. If its running too hot, IMO, it' something other than under hood temps.

I think the flaps you installed will cause more problems with ground clearance, and will certainly degrade airflow UNDER the car and increase fuel consumption on the highway.

Good luck, but I think you're chasing ghosts....

 

^^^Some of us are just interested in the cab heat aspect of all this. As in running alright, hot like hell in the car.

 

Plug them thar holes in that thar firewall!

 

This car I think I need some kinda space shuttle insulation.

 

Three layers of Jute stuck on with 3M high temperature spray!

 

As said above here, pulley arrangement might have a bearing on this case. Chrysler used a lot of different pulleys on all of their engines. They also used different water pumps for AC and non AC cars. The AC water pumps had a 6 blade impeller of smaller diameter than the non AC that had an 8 blade impeller. Then the AC water pump pulley was a smaller diameter than the non AC equipped engines. It was this way on both small block and big block vehicles. So the AC cars the water pump was driven faster than the non AC one.
Then if there is a vapor lock problem, #1 block off your heat riser under the intake manifold, #2 Try one of the new Street Demon carbs- the one with the black center body-they keep the fuel a lot cooler!. I used to have bad vapor lock on several vehicles that I have or had. I use the famous Carter Thermoquad, I love them and no vapor lock.

 

He's already made his mind up. Doesn't matter what you might recommend. It's "too hot".

 

I think your air dam is a good idea but as someone else mentioned should be moved forward directly under the radiator. An air dam creates positive pressure in front of it and negative behind. When positioned correctly will push air up into the rad in front and help pull it thru behind.

 

I don't know if this has been covered, but never buy the swap meet electric fans. I had a Chevy II wagon that would actually overheat on the highway, swapped the fan with a mechanical and a shroud and the problem went away. It was just in the way and didn't move enough air.

If I do run an electric fan now, I only mess with Cooling Components. Huge difference in quality and airflow.

 

I'm confused. If you can run the engine all day long while parked with the hood down and the temperature doesn't get too hot, how in the world can the problem be "trapped" hot air while driving when air is being pushed through the radiator? By the way, I always tell people that English teachers don't know much. I also add that retired English teachers know less. I'm a retired English teacher.

 

Engines don't generate a lot of heat idling. They generate much more heat making HP. At best, an engine is only less than 30% efficient. That means over 70% goes into heat or wasted energy. If an engine is generating 100HP to cruise you down the road, there is over 230 HP in heat that goes out the exhaust, radiator, block, heads, etc all of which starts out under the hood. Since there are 2545 btu's in 1 HP, that means there is over 500,000 btu's in heat that must be removed. A lot of it goes out the exhaust but there is still a lot under the hood, mostly removed by the radiator. Now, do the math for 500 HP or more......

 

If it's taking a hundred horsepower to cruise down the road you must have the emergency brake on.