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SteveJ

Can't maintain fuel pressure

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I'm sure Steve has his reasons for the electric pump but I like to believe the mechanical works fine. Dizeased runs them on his built up motors without issue. My guy told me the mechanical pump would run triples until higher rpms.

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Yes, I do have a reason for the electric pump only. I don't want to remove the head and open up the window for the mechanical pump. LOL 

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My 73 had a much larger and heavier exhaust manifold than the earlier models. Thus more heat sitting under the carbs. I changed to the earlier one when I swapped out to round tops. Thanks to Chet Wittel for the idea. The attached photo gives you an idea of the size difference.

Manifold.jpg

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19 minutes ago, siteunseen said:

That's a darn good reason! What are using, p79?

N47 Maxima head

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Just now, siteunseen said:

You get the bigger valves too? More air flow = less heat, I think.

I'm not sure. Since I didn't put the engine together, I didn't have a chance to take measurements. I'd have to research that. The combustion chamber is smaller, so I get higher compression.

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Steve,

I want to know the outcome of your Project. You see in addition to the stock heat shield which was installed in the car by the Factory originally, i have mounted a stainless Steel heat shield extension that reaches the bottom of both 3 screws SU Carburetor float bowls and the percolation is still present. The gasoline in Panama has no ethanol so this should not be happening. The heat comes from the manifold and thus there must be away of lowering that amount of heat so it does not affect the fuel that is inside the foat valves and that will evaporize and consequently shut the engine down. I am hereby enclosing pictures of the heatshield extension and the new downpipe of the MSA PREMIUM EXHAUST that is connected to the stock manifold for your perusal. Some guys in these fórum only throw out ideas such as swapping metal fuel rail with 5 inch rubber hoses or driving with the lid off? Is this really going to help and avoid the car idle becoming lumpy at traffic jams which leads to a sudden shut down of the engine? Wouldnt it be better to put an ice cooler to lower the temperature at the manifold? Heat shield SU CARBS.jpg

Heatshield SU CARB rear.jpg

downpipe manifold.jpg

Edited by jalexquijano

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anyone? i guess its time to install a blower that can blow air between the manifold and su carbs float bowls thus mantaining that área cool and avoiding fuel percolation.

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In an effort to keep heat of the fuel rail, I added DEI heat shroud to cover the existing insulation. At first I tried 1 inch, but it was too small, so I bought some 3/4 inch and cut it in half. I notched the shroud to go around the fuel rail mounts and where the fuel lines go out to the carburetors.

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