I have a carbureted 302 on my 2wd 1985 Ford F-150. I just got an Edelbrock Performer dual plane intake manifold (non EGR) and a new 470cfm Holley Truck Avenger carburetor. I was wondering if I should go with a 1" or 2" phenolic 4-hole carb spacer, and why? What exactly does a carburetor spacer do?

 

phenolic carb spacers are used to insulate the carb from the engine to prevent the gas from boiling in the bowl due to heat soaking.

1 inch is usually fine, but if you have the room for a 2 inch, or get allot of under hood heat from hot places like in Florida go with the 2 inch

 

i would go with the 2 inch 4 hole spacer. just make sure you have the room to close your hood.
i have a 86 f250 that i put a 400 c6 4x4 in with a edl intake non egr, edl 600 carb in with headers and i put that two inch spacer and i could really tell a nice difference in the response and power. if you are looking for more power, i mean get up and go and driving and need to pass that slow a$$ infront of you that 2 inch spacer will help you a very good amount. i love mine and dont know why i didnt put one under the hood when i first got the truck.

 

If I remember right, theres not much of a price difference between the 1" and 2". I bought a 2" for my '73 and it fits just right. Keeps 'er nice-n-cool. Now if I could just get it to idle right!