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  #1 (permalink)  
Old 09-03-2014, 02:05 PM
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Exclamation Looking for a small structural material that doesn't conduct/transfer heat.

Maybe some of you more familiar with materials can help out... Here's my problem & my plan to fix.
On a warm day when I stop the car after driving, my fuel log warms up & heats the fuel. If I can't get it righ back out on the road, it doesn't really cool off & I need to adjust my idle screws to compensate. This is far from ideal. So the fuel log it attached to the Y-manifold (coolant) by aluminum uprights. What I want to do is cut a section of those uprights out & bolt in a piece of non conductive material, much the shape of the aluminum flatbar, which the uprights are made from, in the hopes that the heat stays with the Y-manifold.
I do have some carbon fiber sheeting, which I can sandwich together to make a sturdy piece. However it seems that CF does conduct some heat. Any Ideas?
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Old 09-03-2014, 02:53 PM
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Wood, bakelite,
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Old 09-03-2014, 03:34 PM
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I thought about wood, not sure how that would hold up. I'll look at Bakelite.
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Old 09-03-2014, 03:42 PM
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Phenolic. I think you can buy it from McMaster-Carr in several thicknesses and sizes. It can be cut and machined.

Similarly, when I got my car on the road earlier this year, one of the first problems I had to contend with was fuel percolation due to a combination of crappy CA fuel and heat soak in a hot engine bay. Once I stopped the car hot, I had a heck of a time restarting because the fuel would boil in the bowls once fuel and air flow stopped. The solution was straightforward and effective: I first added a phenolic spacer (Jomar 5025 from Jegs) between the carb and intake manifold, and that pretty much solved the problem. Since hood clearance is an issue for me and many others, I found just one 0.25" spacer (most of the others were thicker). That was all I needed. After that, just for some extra margin, I insulated the fuel lines going from the regulator to the carb (AN -6), and also a couple feet of the fuel line that feeds the regulator (AN -8) and passes near the headers.
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Old 09-03-2014, 03:45 PM
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Phenolic
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  #6 (permalink)  
Old 09-03-2014, 03:52 PM
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Thank you, sounds like a couple great options. I'll look at phenolic, also.
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Old 09-03-2014, 04:06 PM
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+1 for Phenolic
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Old 09-03-2014, 04:17 PM
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What you are suggesting won't make much difference since the cross section of the thin sheet metal brackets is small. The thin, small cross-section has a hard time flowing heat from the mounting bolts to the tubular portion of the log. The materials being suggested cannot be made sturdy enough in the same thin cross-section, so you will have to increase their cross-section to mount the tubular log. This will increase the heat flux through those mounts and even though they have a lower heat conductivity, the extra cross-section will increase the total conductivity of the mount bracket. I could run some numbers, but I suspect the fuel log is hot from convective heating from the engine compartment air and maybe some radiation from the manifold and valve covers and less driven by the heat flux through the mounting brackets. As a test, you could put some phenolic washers on either side of the sheet metal brackets (and lightly bolt them back in place), which should significantly reduce the conductive heat flux into the bracket. If this solves your problem, you can make a permanent fix.

For a real fix, though, I recommend you put in a return line to the tank, with a regulator. Then, when you get back in the car and begin to pump fuel, the hot fuel in the log will flow back to the tank and be replaced with cooler fuel in an instant. Old cars with old designs had vapor lock and other problems with fuel systems and it sounds like you emulated the old system. That's fine, but you will also be subjected to little annoyances like this.

PS, the fuel volume in the log doesn't help. The fuel flows very slowly in there and is likely nearing full temperature before shutting the car off, so you're probably on the edge of this condition all the time. Decrease fuel stagnation and allow a return so the fuel is not deadheaded and you won't have any issues.
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Old 09-03-2014, 06:40 PM
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phenolic is sort of a generic name for many composite materials
the best heat insulator in a phenolic material would be the canvas/linen grade.
it is strong and heat insulating but deteriorates quickly when wet.
maybe using it as a thick washer would be best and not as the whole supporting piece
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Old 09-04-2014, 05:58 AM
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I agree with iTbites. The heat transfer from the mount is your smallest problem.

I would like to see a pic of your engine bay, radiator ducting and hood to see where you can get rid of heat.

My best version was: All aluminium engine, hood cut open like a Grand Sport hood, no rubber seal to hood, no inner fenders, all air ducted through the radiator, except (this is important) I left the top open to allow air to flow into the engine compartment.

Also open louvers, and you could help evacuating the engine compartment (when driving) by adding a small (Gurney!) flap at the bottom of the foot boxed to create a suction movement.

My headers were never coated, nor wrapped, my foot boxes not insulated. I did have a heat shield between headers and brakes. Maintain a 1" gap between shield and part.

You could try to mount your fuel log away from the motor to see if it improves, for a start.
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Old 09-04-2014, 06:30 AM
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It won't be pretty, but I'd suggest a spark plug boot insulator wrapped around your fuel log. It would need to be modified with holes appropriately spaced for your fuel lines. Jeg's, Summit, etc. carry them. If the spark plug insulator shields are too short, there are fuel line insulation kits that you could cut down to the length you need.

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Old 09-04-2014, 08:03 AM
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Hyde

Think these might help? 48mm Weber Carburetor Spacer 48 mm Dcoe Riser Phenolic Insulator Dellorto 1 4" | eBay

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Old 09-04-2014, 08:30 AM
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Phenolic, you can buy it cheap at aircraft parts surplus houses.
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Old 09-04-2014, 01:36 PM
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I ran all day with Tim & Co, on a nice sunny (70's)day with no problems. As soon as it nears the 80's the "minor" problems occur. A small bump in the idle fixes the problem.
To give a Little history, it was much worse before I drilled a couple sizable holes in the uprights. This is why my thinking has led me to removing a section & adding a different material.
I'm going to think on it a bit more & do a little more testing, based on the suggestions above. Namely, I want to double check the temp of the carburetors.
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Old 09-04-2014, 01:45 PM
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A laser thermometer is a cheap and excellent tool for checking temperatures.
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