I just checked and 1/4" NPT is indeed also 18 TPI with a O.D. of .540 vs. .5625 for 9/16", so I could understand why that works given the tapered threads. And given the ease of availability of a 1/4" NPT plug vs. 9/16-18 bolts, it's certainly the easier way to go.

Splitting hairs, a bolt of correct length would still be preferable as it would bottom-out against the floor of the cavity and not allow exhaust cavitation like a short plug would. As it is though, I'm still a little puzzled by the recommended 2.5" bolt length that I've seen suggested in here. That seems too long.

In my case I was surprised, but happy to see no CEL. I haven't pulled codes - I've heard that some things will trigger a code but not the CEL. Not a big deal either way - worse case you could always just remove the bulb or resort to the Homer Simpson fix. Also, your truck is a few years later, so there might be a higher level of interrogation going on than my '91.

 

I guess I just assumed it was a pipe thread from what I had read before so I didn't even really consider the bolt option. As far as bolt length, they are pretty deep holes. Too short and the head would bottom out before the bolt bottomed out in the hole.

 

Thanks for the quick replys. I'm in the process of extracting all the stuff I need from my parts truck for the Ford in a Chev project, so I won't worry about saving the stuff I don't need. Mine, being from a 94 is speed density as well.

 

If you look at one of the original fittings I think you'll find that it's not tapered. Perhaps the 2.5" bolt recommendation was just to make sure the bolt-end bottomed out, not the head. Regardless, I think I prefer your solution at this point, if only because 6 bolt-heads sticking up would look kinda silly.

As for the guy looking to do the transplant, you should be fine gutting out the AIR, EGR, and Evap stuff - I'm essentially running without all three right now but I've left enough behind so as to not trigger a code. Removing everything, you'll certainly get error codes, but you'll only know they're there if you check! The engine will run fine however - ignore those who tell you that you must go with MAF - you've not significantly changed the VE of the engine, so it'll do just fine on a stock PCM.

 

3/4/13

Can I jump in here??
I have a 1996 F-150 4.9...and I have terrible air/exhaust leaks as described here. Looks like I need to replace the air rail assembly.
Two questions:
What is it's proper name..so I might look to junkyards, eBay etc...or any other sourcing help.
You guys mention just "blocking off" the 6 holes with bolts...seems easy enough...but what else? The air pump with run and pump air to where?

What are the cautions again about MAP vs ? type of emission...
I sure don't want to open Pandoras box...

I hope my interruption is ok...

I joined the list today...and my personal email is bucbean@pipeline.com

Jeff

 

A '96 will have OBDII electronics and will likely be very unhappy about removing emissions components.

 

While I understand that reaction in general, for the "smog pump" removal I don't think it would really be any different a response than a EEC-IV / OBD1 system.

 

Are you sure it's actually the rail that is leaking? That's usually the last thing to get removed (often isn't) since it's well-built and typically requires removing of the intake manifold. All the other A.I.R. stuff can more easily be removed.

Whether you want to actually replace it all is of course a subject of much debate. I will say that getting a replacement rail out of a junkyard may very well be a wasted effort - the fittings into the head are rather fragile and typically at least a couple are seized and thus destroyed in trying to remove.

 

You can purchase the air injection rail here. Scroll down towards the bottom.
PCI Inc. - Aftermarket exhaust and emission control parts

 

Well I was able to get my v-band flanges and O2 bung welded in. I just got it back from from the ceramic coater today. It looks sweet. Now all I need is some time and a little bit of good weather! This weekend would be great but I'm afraid it's supposed to rain Oh well. My schedule is opening up and the weather is generally getting better every day.

I really think I could get this thing going if I had 2 good un-interrupted days, so I'll budget a month. My goal is to have the truck back on the road by the end of May.

Bets on how great it's gonna run with year old gas?

 

You'll more than likely be fine. Ideally you would have put it away with some Stabil in the tank, but since it's just a year I doubt you'll have any issues. I'd throw a bottle of Techron in the tank to help with any varnishing that may have occurred.

 

For anybody who is interested, the 9/16" x 18 x 2.5 are the right bolts to use.

I just did this to my 4.9 when I had it out and I couldn't get 2.5 inch long ones, closest was 3" and I just squeaked by without hitting the lifting bracket which also serves as the washers for the manifolds. I had to turn the bolts just so in order for the flats to clear.

It looks like 2" would have been too short and the bolt head would have hit the manifold because of the angle, so 2.5 would be just right.

Engine looked a little bit like Frankenstein with those huge bolt heads sticking out of it while it was on the stand, but don't really notice them when its all back in place.

Fastenal is where I found the bolts by the way. The wheel studs for our trucks happen to also be the right size and thread pitch, but you would have to either cut the end square or use vice grips to install them which might be a problem if you had to tighten one up later.

I noticed the extreme carbon deposits around the intake ports as well. I think its because the injectors spray fuel over the exhaust gases the egr dumps in and it cakes up over time.

I removed the egr by blocking it off with a plate at the intake, a pipe plug in the exhaust manifold and removed the vacuum lines. I left the solenoids plugged in and I have no engine light, probably have a code for the egr position sensor, but I haven't checked codes since I reinstalled the engine.

No noticeable difference in how the engine runs. I have no idea if the gas mileage took a hit or not since I have never paid any attention to the what I was getting with the truck before.

I got my manifolds to seal well using a trick an old guy I worked for showed me one time years ago. Find a nice flat spot on the shop floor and lay the sealing surface of the manifold down on it and slide it around in a figure '8' kind of like you were sharpening a knife. After just a few passes you can see the high and low spots easily, just keep going until its flat. Then maybe a light Even buff with sandpaper to smooth down the scratches a bit if you have a rough floor. Then copper coat the manifolds, the head, and both sides of the gasket.

Of course you could do it the right way and have the manifolds sent out and machined, but a little home honing is a lot faster and cheaper.

 

Thanks for explaining why the bolts need to be that long. That said, given that a NPT plug has a square or Allen head which doesn't extend beyond the bolt diameter, it shouldn't have the issue with the bolt-head interference. That would seem to make it the better choice. From a practical matter, it would seem that 1/4" NPT and 9/18-18 are essentially interchangeable for our purposes here.

 

That's a pretty cool trick, especially if you know the shop floor is level and your manifolds aren't too warped.

 

Yep, you want to pick a relatively flat piece of floor to use, had to look around a bit in the shop for a spot for the intake that was large enough and flat. I move the whole assembly around in quarter turns as I go, don't really know how much difference it really makes but I feel better if I do, lol.


I tried the 1/4 pipe plugs first since I had some in the shop but they felt really loose. They may have tightened up if I ran them all the way down, probably would have when they bottomed out, but I didn't want to find out I had a problem with the plug after it was all the way down in the hole.

Also, I had the kind with the square sticking up to tighten them with, not the ones with the allen head and nothing I had handy fit it very well and would fit down in the hole besides.

Fortunately Fastenal is only half a block away from the shop. Had to buy a pack of 10 though, was just a little over $18 for grade 8 if I remember correctly.