Vapor Lock and My Next Project

My next project is a set of louvers for the fenders of my pickup. I want to get heat out of the engine compartment. I have a '75 Dodge truck, and at the back of the fenders is a perfect place to install vents.

I plan to cut the existing sheet metal of the fender in squared-off C-shapes to form the louvers. They'll be rather shark-gill shaped inward louvers, aimed to get the heat out. Then I will clamp the fender sheet metal between sorta-sawtooth shaped 3/8" mild steel stock. Hard to describe, but easy to draw. I'll screw the two pieces of stock together from the back-side with 1/4-20 screws and locktite through the sheet metal.

Alternately, I will make louver assemblies in the shop. I'll slot the bar/plate stock and insert/screw individual louvers into the slots. Then, I'll just cut square holes in the fenders and screw the assemblies to the fender from the backside. Probably the easier approach, but I'm not sure it would look as nice. Probably would allow for more heat exit with these simpler louvers.

This is actually a practice run for putting similar louvers on my custom New Yorker. I've got a wicked vapor-lock problem on it. So, I am looking to reduce the under-hood temps. I have a high-tech ceramic coating on the manifolds to keep the heat down. I have a good electric pump at the tank. Those helped a lot. Hot starts are always a problem. I have actually seen hot gasoline fountain out of the carb when the gas in the carb boiled. I have a heat spacer under the carb. Heat cross-over is blocked-off. I have a valley pan under the manifold. So, I'm trying other stuff. Even if this project doesn't help, it will look cool.

Kent

We are having the same problems on my old mans 55 Bird. His pump is down on the frame just in front of the tank. If we cannot find a solution, then a return line will likely be used. Jegs sells a return point for the tank that is located in the filler tube. Just gonna mount the regulator after the carb and run a high pressure style pump.

HTH

Aaron

Since heat rises, wouldn't fender louvers we eliminating hot air from below the level of the carb? Wouldn't hood louvers provide better results?

Good luck, and please let us know how it works out.

Y'all have a great day!

Anthony

How 'bout this! I've got a catalytic converter in the pipes. So, for brief moments, the exhaust acts like a closed system, until the pressure can bleed through the cat. In a closed system, all parts want to be at equal pressure. So, it's possible that the engine is using the exhaust crossover to equalize pressure between one side exhaust and the other until the pressure can bleed through the cat. The quickest path to equalize the pressure would be through the exhaust crossover. It would be faster than down the pipe to the Y and then back up to the opposite manifold. So, even with the crossover butterfly open all the way, exhaust would be pulsing back and forth under the intake all the time! This would boil any carburetor! With the old open pipes, there was no time to balance the pressure from one side to the other. It would just blow out the biggest opening.
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Buzzman72 made me think about the crossover, itself, a little more. I thought I had the exhaust crossover blocked, but I'll bet you dimes to donuts a "helpful" mechanic somewhere along the line re-opened the passage! This kinda confirms what IDJ said about if the vapor lock keeps going, even when I have a pump all the way in the back. This also makes sense, because all the mid-70's cars started having this problem when they started putting catalytic converters in the cars.

I mounted an electric fuel pump directly under the gas tank and had no more problems. To have done it properly, I probably should have bypassed the mechanical pump on the engine, but you can't argue with results. If there was any vapor in the mechanical pump, the electric pump pushed the fuel through, regardless.

You are working too hard to solve the problem, mount an electric fuel pump out of the engine compartment , down in the frame rail is a good place . With a cool fuel pump your problems will vanish. Many years ago I had a 1950 GMC gas road tractor with that disease , being that it was no beauty, I mountd the pump on the fender between the fender and the gas step tank . Problem vanished.

george

I have already tried an electric pump, back at the tank. That helped a great deal in avoiding vapor-lock. At traffic signals, she still tries to lock, though. Hot starts are very difficult. When diagnosing, I have literally seen a fountain of boiling gasoline shoot out the vents on the carb. I already have a plastic spacer under the carb. I've got a valley pan under the intake. I've blocked the heat crossover. I've got a racer friend I've been bugging to install a return line and pressure regulator for me, but that won't help the hot soak. So, I'm trying to reduce under-hood temps. I LOVE the car, so I'm determined to lick this! And it's a hobby. Hobbies are designed to absorb time and money. :-)

I shot an e-mail off today to Edelbrock. You can use a Mopar B-block manifold on a Mopar RB-block engine, if you use spacers. So, I was thinking "If only they had plastic or phenolic spacers to block heat from moving from the block to the intake..." Worst case, I go online and get a pair of spacers to use as templates, and then find a way to make the parts myself.