I have a 289 in my 53 PU with a edel. Aluminium manifold and a 1405 carb. I have a couple FE engines that i have to run phenolic spacers on for the heat. Is the spacer a good idea for the small block 289? Was thinking going with about a half inche spacer???

 

A spacer of just 1/2" should not affect the engine performance very much, and if if insulates the carb from the intake manifold, I would go ahead and use it. But I would also try to find out why the intake manifold is getting so hot. Did you install the intake manifold? If so, did you punch out the exhaust passage hole in the intake gasket? This puts hot exhaust gasses into the intake manifold for heating it up faster when cold. You might consider installing new gaskets, with one side or both sides blocked. Then the intake manifold won't heat up as much.

 

Different types of phenolics spacers, depending on heat, or how hot its getting. Looks like they can range from 265F to 465F. Thermoset Plastic Phenolic Laminates

 

Ford engines typically use a one inch thick aluminum carb spacer.

 

The aluminum spacers are usually for supplying a manifold vacuum port, not for heat insulation like those phenolic spacers.

A spacer 1 inch tall may actually affect the flow enough for you to measure. It's like increasing the plenum size and runner length.

 

I had mentioned the stock spacer as a point of information, not necessarily recommending one. The early engines (1964 and prior in Canada) still had them even though there was no PCV port or other port in them, so Ford must have designed (or tuned) the engine assembly with an inch spacer in mind.

Depending on the carburetor and manifold, there can be interference between the carb linkage and manifold if a spacer isn't used. Of course a non-stock manifold may be designed with the carb boss higher, thus in effect have an integral spacer.

Although a phenolic spacer is a much better insulator, an aluminum one with a paper gasket on each side probably does a fair job as well, or more correctly the two paper gaskets do.