I have a aluminum police interceptor intake manifold. With a strait edge layed across the intake port gasket surface (front to back) I can get a .006 feeler gauge under it in the middle. The other side is flat. Will the intake gasket compensate for this gap? Can a machine shop mill this flat? If they mill, say, .010 off both sides will it still bolt to the heads ok? Will the ends need milling also? I use silicone instead of end gaskets. Thanks....

 

With the intake, if you mill the sides you have to mill the bottom mounting surfaces also or your gap justs gets bigger betweenthe manifold and heads.

 

Cut just the minimum to just clean up, the end jasket gap is so wide it shouldn't cause a problem. I would check with a old pre crushed gasket to make sure the intake doesn't sit too low and cause a top of port misalignment.
Did you also ckeck for twist as the runners can be straight but the intake twisted then two diagonal corners sit low and the opposite high?
I have milled a few intakes on the Bridgeport at home without any port misalignment problems. Different manufactures of gaskets come in different thickness that help correct port alignment after.

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Now the whole truth...the intake is already on the motor and it has about 1000 miles on it. I noticed the gap before it was installed, and took it to the shop that did the machine work. The machinest thought the gasket would compensate for the gap and it would be alright...The engine hunts for a consistent idle but runs great when above idle. It doesn't smoke or use oil and the plugs look perfect. It has a whistle that I can't locate, it sounds like it's coming right out of the intake under the carb. Is there some way to verify for sure, that the intake is sealed?

 

I would spray carb cleaner around suspected areas, if the idle changes you located your leak. With your "machinest thought" he is an idiot in my book as FE intakes can be a problem sealing with everything correct, why stack the odds against you before you install the intake?

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With the engine at idle, spray some Chem tool or wd40 along the gasket mating surfaces. Any change in idle = leak.

 

I tryed the carb cleaner on the outside with no luck. I was thinking of an internal leak. What if I sealed off the carb hole, sealed the vac ports, pulled the rockers. Then pulled vac off one of the ports on the intake???