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Better carb heat shields to deal with vapor lock?

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M

MGNoir

Jedi Hopeful
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I've had problems with my Midget in hot weather with vapor lock. Now that I'm driving it in Texas and summer's coming on, I know it's going to be a real problem very soon - one I'd like to fix.

I was looking at these heat shields for the TR (link below), and the idea makes sense...

https://www.the-vintage-racer.com/webroot/Heatshields/

Anyone know of such a beast for the Midget? I confess I don't know my TR carbs to know if any of them would fit.

Also, any other suggestions for heat? I imagine that most of the heat problem comes from the carbs and the fuel float chambers getting too hot, and not from it getting hot as it comes up the fuel line.
 
Re: Carb heat shields to deal with heat & vapor lock?

By the way I have the default stock heatshield there, but not a fancy "wrap around" style like linked to above.
 
Re: Carb heat shields to deal with heat & vapor lock?

I'd think a stock heat shield would be fine.
Do you have a picture of your current setup? What type fuel pump and where is it located? How do you know it is vapor lock?
 
Re: Carb heat shields to deal with heat & vapor lock?

Assuming your problem is indeed heat at the carb...

I have to deal with hot, humid Tennessee summers, often in traffic. With my setup, single HIF6 & LCB header, vapor-lock was sometimes a problem for me, too.

As I am sure has been noticed, I have no qualms over keeping things original; I do whatever it takes to make things work; better if possible.

That said, I solved my heat-related issues by installing one of these "Aluminum Inferno" heat shields:

https://www.verociousmotorsports.com/Shop...Inferno-Shields

And then also adding a small electric fan (Yamaha R1 radiator fan) which is readily and cheaply available on eBay.

Thus:

PICT0035-3.jpg


PICT0034-1.jpg


Just a thought.
 
Re: Carb heat shields to deal with heat & vapor lock?

Here are some pictures of the current setup.

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Basically this happens when the temperature gets up in the mid/upper 90s and I drive around. Starts running really rough, and fuel just percolates/spits out of the overflow of the forward fuel float reservoir. I've attached a long hose to it (visible in first picture) so if it does it, the fuel is at least not going down near the manifold.

The fuel pump is in the back - tucked up by the trunk and fuel tank.
 
Re: Carb heat shields to deal with heat & vapor lock?

I cut and paste the tag from PhotoBucket; however, using a link as you did is fine. Uses less bandwidth.

I looked at your photos, and my solution to the problem is inappropriate to such a nice engine bay.

Are you sure of what's causing your problem? How's the fuel tank vent? Had that issue on one of my cars once, and it took forever to track it down...
 
Re: Carb heat shields to deal with heat & vapor lock?

Good question about venting, I'll have to look into that.

I don't know if the gas cap is a venting type, but it isn't the tightest fit in the world. I've never had it "whoosh" any air when I remove it.
 
Re: Carb heat shields to deal with heat & vapor lock?

I think Bill is onto something. The poor running may actually be caused by a rich condition as pressure builds in the tank and pushes fuel higher in the float bowl. Is your fuel cap vented?
 
Re: Carb heat shields to deal with heat & vapor lock?

OK, so what type fuel pump? SU or aftermarket?
 
Re: Carb heat shields to deal with heat & vapor lock?

Let's see. The fuel pump is an SU type, and the gas cap is... well... whatever came with the car I think :smile: Below are links to pictures. Doesn't look very "venty" to me...

https://www.flickr.com/photos/falcon_ship/4584576949/

https://www.flickr.com/photos/falcon_ship/4585203890/

So if it were a case of the tank and venting (versus heat), would there be a way to tell based on the fuel pump sound? In other words, would the pump run more (tick, tick, tick) or sound different in one case over the other?
 
Re: Carb heat shields to deal with heat & vapor lock?

I think the pump would sound the same, but excess tank pressure would create excess fuel line pressure. It is just a theory.

However, I'm pretty sure a better heat shield is not going to be the answer to your problem.

It could just be that your float and valve doesn't work well when hot and they need to be replaced.
 
Re: Carb heat shields to deal with heat & vapor lock?

One of the things I did to stop this on the weber was to make my own super thick phenolic gasket to stop the transfer of heat from the aluminum intake manifold (that is just absorbing that heat from the exhaust manifold) to the carburetor. Yeah the carb gets heat conveyed from the exhaust manifold but that intake temp gets pretty high a puts direct heat into the carburetor.
 
Re: Carb heat shields to deal with heat & vapor lock?

So if it were to happen, I would only have to pop the gas cap to see if it was tank pressure, correct? Still a problem means not the tank venting.

I'm thinking of ways to debug the problem as it were.

Tim
 
Re: Carb heat shields to deal with heat & vapor lock?

Seems reasonable
 
Re: Carb heat shields to deal with heat & vapor lock?

Cover the fuel filler with a heavy peice of alum. foil, use a heavy rubber band around it to hold it on. [censored] a small hole in the middle.

If your problems goes away you found the son of a gun.
 
Re: Carb heat shields to deal with heat & vapor lock?

Ack I never thought of the fuel filter. It sits right out in the open "protected" by a thin plastic shell.
 
Re: Carb heat shields to deal with heat & vapor lock?

Yep, the heat shields have never really given any problems, so I look elsewhere as folks have mentioned. That first link for heatshileds, thats Joe Alexander, he make nice stuff, but most of it is for Triumphs.
 
Re: Carb heat shields to deal with heat & vapor lock?

If it helps, I had a terrible problem with vapor locking, but it turned out it was the mechanical fuel pump that was getting hot. Hot enough that when it stalled out, I could open the cover on the pump where the inlet screen is, and hear fuel boiling. The engine wasn't overheating though. Finally fixed it by bypassing the mechanical pump and using a Facet pump. It dawned on me that this could be why the '78-'79 models had a thicker spacer between the pump and the engine.
 
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