How do you know if carburetor spacer is needed? - Ford Muscle Forums : Ford Muscle Cars Tech Forum
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post #1 of 2 (permalink) Old 06-09-2015, 04:05 PM Thread Starter
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How do you know if carburetor spacer is needed?

i just picked up a holly 650 dp from a buddie of mice for a smoking deal of $50 and i want to put it on my 351w im dropping in my mustang soon soon but ive read a few things about spacers. how do you know if you need one? i know that the holly has an electric choke and a vacuum advance but im not sure if that has anything to do with it. my 2 barrel on my 289 has a spacer with a hose going from the valve cover to the spacer, what is the purpose of that?
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post #2 of 2 (permalink) Old 06-29-2015, 01:39 AM
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Re: How do you know if carburetor spacer is needed?

The spacer helps with bottom end torque if it has four holes and top end if it has one big hole. It also helps to isolate the carburetor from the intake manifold and the heat that is inherent to it. IE> Colder carburetor, denser intake charge. Less chance of dieseling when shut down. Some fords has a hose from the water pump to the under carb plate. This was to help warm the carb for better cold performance. Others had an exhaust port run thru the plate for EGR purposes. I run two four hole plates on my dual quad for better bottom end torque. I still have plenty of pull in the upper end, but I can drive the thing from light to light without any problems with hesitation or bogging.
Good luck and have fun. Its supposed to be fun
The Roach

P.S. If I were you, I'd look into changing the power valves in that carb. Chances are the previous owner had a backfire at sometime in the past and that always blows the power valve in a Holley carburetor.
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