Extra Slot In Intake

[Grizzly]

Just pulled the holley off my 300hp 327 and found a slot running cross ways in front of the primary holes in the manifold. The gasket had a special slot in it too, but on top of the gasket was a thin stainless spacer that sealed the hole.

What's if for and do I have to get the special gaskets and seal it up again?

Help, I want to get back on the the road!

 

[JohnZ]

That's the (in)famous "hot-slot" design that was abandoned in 1969; it routes hot exhaust gases from the crossover passage up across the carb base for improved cold-start driveability in the winter. Unfortunately, even though the stainless baffle is there to protect the carb base from direct exposure to the hot gases, the intense heat can still distort the baseplate and cause percolation of fuel in the primary float bowl.

I recommend blocking the passages at each end with 7/16" steel freeze plugs to stop the flow of hot gases (see pic at link below). On Q-Jet-equipped cars, this design caused the biggest fuel system safety recall in GM history in 1969; the heat melted the soft plugs in the bottom of the float bowls, which resulted in engine fires.

I have a "Tech Bench" column coming on this same issue in the October or November issue of "Corvette Enthusiast" magazine.

 

[magicv8]

As an altervative, I tapped the holes and inserted hex socket locks into the threads. I used a magnet to pull out the thread debris - since I did it with the manifold on the engine - about 8-9 years ago.