I have a quick question. I disassembled a holey 4150 carb and didn't realize that two of the eight screws were different length. I am only used to seeing the shorter screws (3/4" under head length) but two of them are 1" under head length. Any idea what holes the longer screws are from? There two center holes between the throttle plats are blind holes and only fit the short screws. But I could have sworn one of the longer ones came from those holes. It is possible someone was into this carb before as I found the fuel fitting JB Welded to fix stripped threads.

Holley hasn’t put any screws in the holes between the primary and secondary blades in many years.

In many applications, those screws are open to the plenum and can fall into the motor.

Most of the newer design baseplates don’t even have the holes there.

Just use the 6 correct length screws, and leave those two out.

I may do that. I am freshening up the original carburetor on my friends 1970 Z/28. Had some leaks. Also appears like the choke well is leaking hot gases as the vacuum secondary diaphragm and fast idle choke cam were melted some. I feel weird leaving out two screws on his carb. As I mentioned, the long ones seem to have come from the center holes. But those holes don't appear to be deep enough to accept longer screws. I don't want one to find its way into the engine. So I think I am going to leave them out.

Well, I’m sure that original 1970 carb had all the screws.
Aren’t there a couple of positions where they aren’t blind holes,
Just put the long ones there....... or cut off a couple of threads.