Ok guys I just got my EFI manifold to put on my 78 and I remember hearing something about one of the flanges needing to be groud off, but I couldnt find it and I cant really remember. Any help???

 

Just ordered efi's for my 1966 f100. Would also be interested.

What other mods are you making to the exhaust?

 

Ive got the Walker Y-Pipe 2 1/2 inch into a 2 1/2 inch Flowmaster 40 and then its going to have a 90 degree bend out in front of the rear wheel.

 

Sounds excellent. I'm also looking for an offy intake and holley 390.

 

My 1982 did not require any grinding for the OEM intake. I mated every thing to an engine that was on a stand. But then I found an Offy for sale local. I did not grind an on it or the EFI exhaust. I don't know about the year differences of the!

 

Just finished putting an EFI manifold on my 84 Had to trim off the rear lug on the front manifold and also had to trim a lug on the side of the manifold at the back of the elbow. Just did it witha hacksaw and a file. It fits much better than the origional manifold. Used the walker y pipe new cat, mufler, and tailpipe everything fit fine. Huge difference in performance.

 

Where do you guys get the Offy C and Holley 390? Local? Junkyard or retail? Internet? Catalog?

Jeg's seems to be a good source. Don't want to pay the high prices for Clifford Performance.
Lou

 

I have found all of my stuff online through ebay headers $89 new $112 shipped to my door. Fordsix.com $150 for new offy c series intake shipped to my door. Ebay rebuilt holley 600cfm for $84 shipped. Ebay new holley air intake $19 shipped. Gaskets Napa $13.99. driverfx.com muffler $19 shipped. Y pipe made my own.

 

E-bay is a good source for many 300 parts.

 

I found most of my parts at local parts stores and Summit Racing. I found that the starting price on Ebay plus the shipping was too close to new price to take the chance.

 

I replaced the entire exhaust from the manifolds to the tailpipe on my '85 F-250 4x4.
A local "U-Pull-It" wrecking yard had a an '91 van that I was able to salvage the EFI manifolds for $15.00 a piece.
On the #4 cylinder, I believe I had to grind off the top tab. Just put the intake and exhaust manifolds gasket side down on a flat surface as if you were bolting them onto the head and you will see which mounting tabs on the #4 cylinder need to be trimmed.
Here are the Walker/Dynomax part numbers for the 2.5" exhaust system:
1. #45166 - Y pipe that connects to the two EFI manifolds
2. #15142 - Catalytic converter with air injection
3. #17788 - Dynomax muffler
4. #45213 - Tail pipe that exits behind the right rear wheel.

You will also need to go to a local muffler shop and get a 27" length of straight 2.5" tubing which will connect the cat and muffler. This length may be different if you do not have a 133" wheel base (8' long bed).

While I was at the wrecking yard getting the manifolds, I also got all of the factory exhaust hangers with the rubber mounts.

This exhaust system was a very simple bolt on setup which did not require any pipe expander tools to mate the various pieces together. The only tools required were to bolt the Y-pipe to the manifold studs. I then drove to a local muffler shop to wire weld all of the seams and install the J-hooks for the rubber hangers mounted to the frame.

I used a Mr. Gasket #260 intake/exhaust gasket with bunch of hi-temp copper RTV silicon to ensure a good seal.

Good Luck!