In those two cases, more than likely either never set up properly or the added manifold vacuum made very evident a gigantic vacuum leak.. Aluminum intake manifolds? Very few people, especially shade tree mechanics, know how to properly torque down a manifold.

Purely speculation, but bet I'm in the park.. However betting against being too small of carburetor, there is just no scientific evidence to support it.  I have never heard of such a thing. Not saying impossible mind you, just can't make it work in my head.

GT

One engine was running an aluminum "performer" the other one was running a complete stock engine with the only change being from a quadrajet to an edelbrock ( initial reason why this topic peaked my interest ). When the first engine was rebuilt, I made sure to up the carb. Engine is heading into it's second season running solid.

If we go by your previous example, air draws fuel in... Which I agree with. Then if there is less air being drawn in, then there is less fuel too...




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Thank you for the education.  A little history, my barge is a 21' day cruiser, family boat that will never see 50 mph.  The engine is spinning a stock Jacuzzi YJ pump.  Fully loaded it tips the scales around 3,000-3,500 lbs.  Because of the weight of the boat & the pump's limitations, I am bascially limited to 5500 rpms.   So I didn't build the engine to max horse power, but more for economy & low end torque.  This is why the choice of a Edelbrock 650 carb. 

As to tuning it, I will be out on the lake Mother's Day weekend with my new jets, springs & metering rods. 

BTW the cable extension from Edelbrock worked like a charm.  Cut it to length & all is good.

Thank you all for sharing your knowledge & experences....-Rich