1985 GT 4bbl Y-Pipe Questions

[TopGear85]

I have a 4bbl 1985 Mustang GT that is in the shop right now getting some major work done. One job that got completed was to install a new clutch, pressure plate, clutch release bearing, and rear main seal. My 85GT has 1986 headers that were put on by the previous owner, but I was able to locate a correct pair of 85 headers (with the heat risers) and I figured that since the exhaust needed to be removed to do all the clutch work, I may as well have the shop install the correct headers. Anyway, I spoke to the shop today and they said they put the 85 headers on, but they couldn't get the rest of my exhaust to bolt up? They said it was close, but that the 85 headers just wouldn't match up with my Y-pipe.

My question is...did the 85 CFI cars use a different Y-pipe that wouldn't bolt up to the 85 4bbl headers? I thought I had the correct Y-pipe, but if I did the shop should have been able to reconnect my exhaust to the 85 headers. That got me thinking that maybe I have a Y-Pipe for a CFI car and that's why it won't bolt up? I thought I remembered JACook saying that there was a difference in the Y-pipes for CFI cars?

Can anyone help me with this question? Does anyone have pictures of each Y-Pipe so I can see the difference (if there is one)? Why would the 86 headers bolt up, but not the 85? I told the shop to put the 86 headers back on because I can't run open headers, but I really want to run the correct 85 parts (if I can). I just don't understand why these headers wouldn't attach?


Any help and pictures would be greatly appreciated.

[bluesfannoz]

Here is a picture of the Y-Pipe that I acquired from a 85 5spd car. Sorry don't have one from a CFI car so I do not know if they are different.

[TopGear85]

Thanks for posting! I'm sure somebody will have a CFI Y-Pipe pic so I can compare them. If not I'll just check your pic against the pipe I have on my car and see if they are the same.

[Saturn V]

From what I understand, the CFI y-pipe does not have the small lightoff cat on the passenger side, but the carb y-pipe does. Do you do have the little flapper valve (heat riser) on the driver's side? The 85 carb header has a flat flange on the driver's side and you need the flapper valve to provide the ball socket connection to the y-pipe. (Of course, the flapper valve's main purpose in life is to close and direct all exhaust through the passenger side lightoff cat at startup, via the exhaust crossover passage in the intake). Take a look at the following thread for pics, dimensions, and part numbers of some different y-pipes. Post #17 shows the flapper valve. If you have pics of your setup, post them up.

http://vb.foureyedpride.com/showthre...ng-5-0-exhaust

[TopGear85]

No I don't have that valve. All I have are the headers, the Y-pipe, and the rest of the exhaust. Are you saying that I need 1 of those flapper valves (for the DS only) and that connects directly to the header and the Y-pipe? Like it goes...cylinder head---header---flapper valve---Y-Pipe---rest of exhaust? I only need 1 flapper, not 2?

[JTurbo]

Should only be 1 flapper on the driver's side. I have the same setup on my 82 GT....

[Saturn V]

No I don't have that valve. All I have are the headers, the Y-pipe, and the rest of the exhaust. Are you saying that I need 1 of those flapper valves (for the DS only) and that connects directly to the header and the Y-pipe? Like it goes...cylinder head---header---flapper valve---Y-Pipe---rest of exhaust? I only need 1 flapper, not 2?

Yes.

I haven't been able to find a source for an OEM flapper valve, but Rock Auto and others sell replacement parts. However, they list the same part number for multiple years and I believe the 85 flapper is larger than previous years. So I don't know if the replacement part is really for 85. To at least get your car going, you could see if your local auto parts store has one, or can order one. Then, get it in your hands and compare the measurements to the one in the thread above. If it matches, buy it and use it until you can find an OEM part, if that matters to you.

[TopGear85]

Is the technical name a "flapper valve?"

[Travis T]

Technical name is heat riser valve.

[TopGear85]

Is this it installed?

[Travis T]

That's it.

[TopGear85]

Why doesn't that one have that vacuum connection (I'm assuming thats what that is) like the one from Rock Auto?

[Travis T]

It looks like that part is missing is all. All heat riser valves had the vacuum can.

[BaconB8]

Mike,

Is this for your 85 Saleen?

[TopGear85]

Mike,

Is this for your 85 Saleen?

Yes Sir. I should be driving her next week (I've owned the car for almost a year and still haven't gotten to drive her). She still isn't pretty, but at least she runs.

[JACook]

The CFI and 4V headers are interchangeable, and the only differences between the Y-pipes is the
CFI doesn't have the passenger side light-off cat, and the connection where it meets the catalyst
is different.

The '86+ driver side header is more or less identical to the '85 header, with the exception of the
heat stove, and the flat heat riser flange vs ball flange.

The reason an '86 H-pipe won't fit the '85 headers without modification is because the heat riser
valve moves the ball flange an inch farther down. The entire difference is exactly the thickness
of the heat riser valve. The '85 ball flange is also a bit larger outlet, but in my experience that has
never been a show stopper.

If you want to use an '86+ H-pipe with the '85 driver side header (passenger side is no problem)
the muffler shop will need to section an inch out of the driver side down tube.

Saturn V, that heat riser valve in your photo will fit the early '85 CFI cars with cast iron manifolds,
but it's way smaller than the one used on the 4V engine, and late '85 CFI.

[Saturn V]

Saturn V, that heat riser valve in your photo will fit the early '85 CFI cars with cast iron manifolds,
but it's way smaller than the one used on the 4V engine, and late '85 CFI.

That's a stock photo from Rock Auto and might not necessarily represent what you get. But it does look small compared to the 85 part and it's listed for multiple years, so I wouldn't trust ordering it for an 85.

Mike, if you decide to keep the flapper valve arrangement, you'll have to scrounge around on eBay (they do pop up occasionally) or maybe here to get a used part. I haven't found an NOS part for sale, but it appears that the correct part number is E5ZE-9A427-AA, per the following site.

http://www.ascmclarencoupe.com/Parts/

[TopGear85]

Will 86 headers fit with an 85 Y-Pipe? That's what my car came with...86 headers attached to an 85 Y-Pipe, but I never got to drive the car, or hear the engine run in the entire time I've had this car. I physically saw the 86 headers bolted up against the 85 Y-pipe, but I don't know if they sealed properly against it, or if they were just rigged together (and didn't actually fit right/leaked/etc).

[JACook]

The '86-header-to-'85-Y-pipe has the opposite problem, for the same reason. To fit properly, the '85
Y-pipe would need an inch added to the driver side down tube. Though since the driver side down tube
on the '85 doesn't have a catalyst, the fitment may be a bit more forgiving of the difference.

I've seen lots of stuff people have managed to make work, but unless you're willing to modify, the '85
Y-pipe needs the '85 driver-side header and heat riser. Likewise the '86+ H-pipe needs the '86+ driver
side header.

[TopGear85]

The previous owner must have gotten the 86 headers and 85 Y-pipe to connect by any means necessary. I must have one huge exhaust leak. I'll just add a new exhaust to the long list of parts I need.

[JTurbo]

In all honesty, unless you're going for concourse resto or need to meet certain emissions criteria (ie Cali), I would just stick with 86 or later headers and h-pipe exhaust on your car....

I've stuck with the stock y-pipe exhaust on my 82 GT, but it's because its what I ended up acquiring when I found the engine/trans donor....

Carry on

[TopGear85]

Right now I just want a leak free exhaust system by the easiest and cheapest means, but I am going for originality in the long run. I think that because I have the Y-Pipe and 85 headers the easiest thing for me to do is find one of those heat riser valves, rather than switch to an H-pipe (wouldn't I also need a double hump cross member).

[TopGear85]

I found a pic of the parts the PO put on the car. Can anyone tell me if these parts fit together properly or if they were just stuck on to make the exhaust appear complete? Here is the pic:

[JACook]

OK first, that is a CFI Y-pipe. And no, it would not fit properly with that style driver side header unless
it's been modified. Am I seeing things that aren't there, or does the passenger-side have a weld bead
around it? If so, it was probably shortened 1". With the smaller manual-trans bellhousing there would
be plenty of clearance to do that to an AOD Y-pipe.

If you just want a system that works, why not keep your existing H-pipe and just use the '86+ header
without the heat riser valve? I'm running the 4-cat Magnaflow X-pipe on my '85 hatch, with '86+ JBA
driver-side shorty. All's I had to do was weld a stub of 2" tube to the driver side header, to match the
'85-spec JBA shorty on the passenger side. Around here, it never gets cold enough that I miss the
heat riser valve.

[TopGear85]

I don't have an H-pipe. The above abortion is what the PO put on my car...that's all I got.