Exhaust vent???
Lead Driver
Joined: Sep 2003
Posts: 7,015
Likes: 208
From: SoCal
That's a one-way valve for the thermactor air injection system that's rusted off. The top opening should have a nipple fitting for a hose that comes from the TAD/TAB control valves that are fed by the smog pump. That air is supposed to be pumped into the exhaust port when the TAD/TAB valves are configured properly by the EEC, and the one-way valve prevents exhaust gasses from pushing back to the control valves.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
There should not be an "exhaust vent" in the engine bay, as mentioned the rest of this system has been removed by a PO or has otherwise left the mother ship, you whould remove the remaining crossover tube and plug the holes in the rear of the cylinder heads with 5/8x1" coarse thread bolts with copper washers to seal. 
Thread
Thread Starter
Forum
Replies
Last Post
buffalobillsexhaust
1987 - 1996 F150 & Larger F-Series Trucks
26
Sep 24, 2014 09:42 PM
