Mystery hole in intake

Does anyone know what this hole is in the bottom of my Edelbrock DP4B intake manifold is? What does it do and should it be plugged? It doesn't appear to lead anywhere...

I would make a air pressure test with a air hose nozzle and see if that hole goes into the heat cross over passage in the bottom of that manifold, if it blows out the sides have that hole welded shut, if not don't worry about it

The plot thickens... So there is a mystery tube involved here, which runs inside the exhaust crossover cavity and exits from the top of the manifold.
i

Heat source for automatic choke. Surely some of you remember automatic chokes on cars.

DING DING DING

yep. unhooked many of those heat tubes from carbs

no need to weld it shut.

but to be on the safe side, air check it like cab said. you never know the complete history of any "old" part. if it does leak into the crossover, you can also tap that hole[or both] to a "xxx" fine thread, then use a short "button head" screw to plug it instead of welding.

What about the one on the bottom? Is it possibly an EGR port?

Joe

NO, this is a hole on each side with a steel tube inside connecting the 2 openings.

egr gasses will heat the tube and the air inside of it to heat the choke thermo spring.

idea is.. as the air inside the tube heats is rises to top of tube to carb choke housing connection. cool air flowing under intake is sucked up into tube and heated.

good idea to air check for leaks though. I have saw them with holes the tube from rust.

How in the heck did the factory put a steel tube through those holes, they aren't even close to lining up??

Not something I've seen before...

Joe

my LD340 has one as well. The steel tube was probably set in place in the empty mold and the aluminum poured in later casting itself around the tubing.

Aha!! we have a winner!!

Joe

correct, during the casting process, pre-bent tube and positioned in the sand mold then cast.

not too bad as I have never saw one with casting shift enough to leak.

I have had to do some good amount of porting to correct casting shift flaws on intakes.

maybe QC inspect and they catch it before hand and melt/re-cast it.

The bottom hole is the intake port for the heated choke which draws a slight vacuum to pull the heated air through.

Mystery solved - thanks!