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A Question About Carb Heat Shields

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Musicman

Musicman

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I was out with the TR6 today. After making a short pit stop where I turned the motor off, it was kinda hard to get it to start again after the car sat for about 15 minutes. This sometimes happens whenever the car is turned off when warm and then going to start it again. Does this have anything to do with the fuel being hot? My main question is would the stainless steel carb heat shield available for the 6 solve this sometime problem?

Thanks in advance for all advice and tips.
 
Hey David,
There are several things happening here that might make your car harder to start after a short rest. You might still have a tankfull of winter-grade fuel in your car that will evaporate quicker than a summer blend. The engine temp will continue to rise for about 10 minutes when you shut it off after a run. Higher engine temps and fuel that tends to vaporize in your carbs and fuel lines will make for lots of starter issues. The heat shield might help although it was really designed for header cars which will throw a lot of heat towards the carbs. Reaching down and blipping the fuel pump a few times might get you some more gas but that is embarrassing to have to open your bonnet at the local Starbucks just to start your car. However, I have been known to do this on occasion just to show off my engine to the yuppie crowd. I think this issue will be less of an issue when the fuel becomes less volatile with changeover to summer blends. Heat shield can't hurt. I also switched to a high-torque starter to kick the engine just a little harder when she is reluctant to start.


Bill
 
Bill,

Thanks for the insight. I didn't realize that info about winter/summer gas. I'll be taking the 6 out again today for sure. I'll see how things go.

Thanks again!
 
Hi David,

A heat shield is a good idea, but Bill is right, in this case it might help a little, but probably not much. The temps underhood continue to rise in the still air, for a while after the car has stopped. It's different with every car, depending upon a lot of factors such as how well the engien compartment is sealed and how efficient the cooling system is. The heat shield is more intended to stop radiant heat when the car is running and in motion, and air is moving around in there and being exhanged for fresh, cool air.

You are probably already aware, many modern cars have electric fans that are designed to run for a couple minutes after the engine is shut off, to address this problem. These fans will reduce underhood temps as quickly as possible. If your car has an electric fan, it would be relatively easy to set it up to function this way. Just connect it to a circuit that is hot all the time and use a thermo-switch to control it.

Some things you might check are the float bowls, if there is any leaking or the needle valves are working properly. It could also be a sign that the fuel pump, assuming an original one, is starting to get tired and is in need of a rebuild.

An alternative is an electric fuel pump, which will pressurize the system the moment you turn on the ignition, doesn't have to wait for the engine to start cranking. A small pump like a Facet can be hidden under the car or in the trunk and can be plumbed through the original pump, so that the car's originality is preserved as much as possible. With Facet or any electric fuel pump, it's important to check that the pressure is not too high, or flooding might the result. 3.5 to 4psi is all that's needed. A pressure regulator can also be used in the fuel line, to lower the output, if necessary.

Hard, hot starting might indicate a problem with the carbs, too. For example, this could be a choke that isn't fully off, due to adjustment. Or, it might be tied to carb synchronization or other issues. A general tune-up (adjust valves, go through the ignition, set timing, change spark plugs, etc.) might be a good idea before fiddling with the carbs, though.

Let us know what happens.

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Was out with the car again today. I'm glad to say there were no problems to speak of. I had occassion to shut the motor down a couple of times and it started right up afterwards each time. What can I say? Tempermental LBC's. Sometimes they seem to have a mind of their own. It's beautiful here today - upper 80's, sun, clear skies. It's truly a great day for cruising with the top down.

Life is good.
 
I'll throw in my two cents regarding the high torque starter and electric fuel pump. My TR4 was notoriously difficult to start when I had the stock starter - after sitting for a few days. The original starter finally gave up the ghost and I went with a gear reduction model. It starts much easier now! That car still has the mechanical fuel pump.

My Sprite has the original starter and an electric fuel pump. The Sprite starts even easier than the TR4... much easier when cold!

I'd recommend an electric fuel pump for starting ease. It's much cheaper than a gear reduction starter, and it can be hidden (if stock appearance is an issue).
 
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