I am collecting parts to convert the old 240 from my 67 Merc to a 300. I want to make a few improvements to tap into some hidden horsepower, one of which is to go with EFI exhaust manifolds. Before I blindly buy a set of EFI exhaust manifolds is there anything to watch out for like differences in manifolds from year to year? Are the ones from a van the same as the ones for a truck? I have seen used ones advertised on line from vans so I am suspicious that they may be different. If I can't find used OEM ones are the reproduction ones (Like Dorman manifolds) acceptable? Please let me know if there are specific ones I should look for.

 

Used exhausts may be severely warped - or shrunk. I suggest you take an exhaust gasket with you to match up to the part. Getting them resurfaced may be good too. Belt sander accuracy is OK.
Also, on your head you will need to add a couple of clips to the undersides to keep them from slipping down, since there are a couple of holes absent.

 

I cant answer about the van / truck manifolds but to find out look up the part numbers for the van and then the truck and see if they are the same.
If so then you know you can use either. Do the same for the Y pipe as I also dont know.
When looking for Y pipes I think I had to look it up as a cat because the cat comes with the Y pipe and the other way around.

On any Y pipe you get look down into the pipes from the motor end.
When they weld on the Y the hole into the other pipe is really small on some of them.
They say you can open it up with a Dremel tool, mine was ok.

I dont know of the clips FF talks of? I replaced the bolts with studs that makes it a little easier to install but you still need 4 hands LOL
You will need to "clear" the manifolds as they will sit higher then the intake and the mounting washers will be cocked.
If you lay the exh & intake on a flat table you will see where the mounting washers sit will not be even.
I also think there was a "tit" on the exh manifolds that hit the under side of the intake but has been a long time since I did the install.





You will also lose the exh heating the under side of the intake that helps with cool weather running and keeps the air / fuel in a vapor.
I use a hot water plate bolted to the intake and run hot water through it before it hits the heater core.
Got the plate off Ebay but you may find them on Amazon?

I have that all going into the factory mid pipe / muffler / tail pipe, no cat this way if I ever need to get they system I can hit any parts store for it.
Dave ----

 

No difference in the manifolds through the years. If there are, they don't affect how they fit.

As stated above, make double sure that both the intake and exhaust manifolds sit flush against the head WITHOUT the gasket before installing. There are several raised ridges on the EFI manifolds (I think just leftovers from the die/casting process) that can interfere with the intake and need to be ground off. The EFI manifolds also have 3 extra bolt "loops" on them that won't be used, as the EFI head has 16 holes instead of 13. One or more of these may also bind with the intake and need to be ground off.

On mine, I used studs and extra thick washers. I needed a combination of 1/2" and 9/16" washers to get it all to fit, due to some of the intake/exhaust tabs being further apart than others. Some of the washers may also need some shaping on the grinder to fit better. You'll see what needs what when you start putting it together.

https://www.nutty.com/washers/grade-...-flat-washers/

I also recommend the Remflex 3005 gasket, as it's one of the best sealing gaskets I've used.

Also not sure what clips are being referred to, as I've never had an issue with them sliding down after they're installed and torqued.

 

Hey @FuzzFace2 Dave, where did you get the Y pipe or did you get it made custom? The cuts might be tricky but I might try this myself if I can't source one. My log exhaust is cracking and I am hesitant to put it back on so I'm thinking of getting some EFI exhausts for my 81 carbed 300. I do want normal single exhaust since I already sourced that and prefer a non-resonating muffler. Yours looks reaaaal nice.

 

That is the Walker Y-Pipe 45166

They are a nice inexpensive pipe, but they're getting more difficult to find. They also are known to suffer from quality issues on the rear inlet. Be ready to do some work opening it up with some grinding.

This is a picture I got online. It's a lot more opened up than the last one I worked on on my cousin's truck. I think on his that hole was about 3/4" across.

 

Is 45166 maybe a longer version of 15739 for when you don't have a cat?
I can't configure any years of the EFI exhaust that incorporates this all.

So for my 133", it seems like a 45166, single 42477 extender, 18238 muffler (which I already bought) and a 46326 tail (which I also already bought) might get it out the back. Anyone able to check my calculations or find the application combination for 45166?

https://www.walkerexhaust.com/find-my-part.html

 

Actually I need to look at the outlets going forward. I have all 2" pipes and it looks like all the EFI are 2.25". Bummer I don't think I can return the ones I have!

 

I think I got it through Rock Auto and came with the cat I did not use.

My 81 parts truck style side long bed had a almost new system from cat back so I used it on my short bed flare side.

Yes the Y pipe is a little larger than my 81 pipes but all I did was get an adapter pipe from Auto Zone and 2 clamps of the right size to make the connection.
Its not real pretty but being tucked up behind the frame who is going to see it?
Y pipe is to the left

Dave ----

 

They say the newer EFI exh system, larger pipes, will fit the 80-86 trucks so if I ever need to replace any of my pipes I will go with the newer large pipes.
But like you I went with what I had at hand.
Dave ----