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I am trying to figure out if my 4.9 EFI has air in manifold or air in head. I am thinking air in manifold. It runs down the left side of the engine towards the cats not in the center in front of the intake manifold. But I am looking at pictures of used 4.9 whether they are air in manifold or air in head all show a tube directly in front of the intake manifold as shown here
I am just thoroughly confused if anyone could be of assistance I would appreciate it.
I'm tearing apart a '94 with a 6 right now. As soon as I get the fenders and cab out of the way, I'll try to get a good look at the system on it and see if we can make any sense of all that.
I know the V8 system really well, but haven't messed with the 6's much - at least not that part of them anyway.
Ok the first picture, you can clearly see it goes into the head - nowhere near the manifold. Then I marked the line with red from the diverter valve to that tube.
On the other side of the diverter (blue) you can see a second line coming out that goes down to a 2nd tube that runs all the way to the back of the motor and down to the catalytic convertor.
So basically the same as the V8's except that the diverter valve is at the front but still directs fresh air from the air pump either through the head or down to the cats.
These pics are of a 94 so I would guess that maybe the earlier ones ? had the air pumped into the exhaust manifold and then changed it to introduce air directly into the head ?
For sure they totally redesigned the 302 heads to introduce fresh air to all the exhaust areas from a single port at the back of the head. Most likely they didn't want to redesign the 4.9 heads so they just drilled and tapped a bunch of holes and installed the tube.
Anyway hopefully the pics are clear enough to see - the setup in the pic shows air going into the head.
Edit - now just to confuse the issue, that tube in the first pic (red) is technically a manifold. Not intake or exhaust manifold, but the definition of a manifold would be an entry port and multiple exit ports... but it's feeding into the head so ...
Thank you for the in depth pictures they are a great help. But my issue is my engine doesnt have the secondary air manifold which you have marked in red at all and I dont see any holes that have been capped off in the head either. I will try and get pictures as soon as I can.
I got a few pics today, as you can tell it has two hoses that run to the left of the engine down to what looks like the catalytic converter but I really can't see back there it may be the back of the head.
You only have one hose coming out of your valve but you have the pipe heading back. Have to get a flashlight and crawl under and see if that pipe splits off at the back or just goes to the convertor.
10-07-2015, 01:03 PM
Air in head/manifold question
