National Parts Depot Y-Pipe

[abrdn419]

Anyone know the difference between these two 2 pipes? I have a 77 Bronco and curious on why one is used with a spacer and the other does not. I want to make sure I order the right one.

thanks,

https://www.npdlink.com/product/y-p...y%2Bpipy&top_parent=80000&year=1977&year=1977

https://www.npdlink.com/product/y-p...y%2Bpipy&top_parent=80000&year=1977&year=1977

 

[904Bronco]

I haven't seen one in a while...
I want to say that on some Broncos there was a preheat butterfly valve on the discharge port of the exhaust manifold. Not part of the manifold.
Stayed closed when cold to push exhaust through the intake crossover to aide in heat up. Idle speeds it would stay closed, above idle the backpressure would cause it to open.

Maybe someone else will chime in to confirm... Doug

 

[DirtDonk]

I would say that is correct.
I’ve never noted with any consistency, which Broncos/vehicles got the flapper valve thingy, and which did not. Seen plenty of them in my lifetime, but certainly not on every rig.

 

[DirtDonk]

Does your full-size have one Doug?

 

[phyler]

My 75 has the spacer/butterfly as part of the emissions equipment. It's stuck open and doesn't do anything anymore other than take up space.

Sent from my Pixel 8 Pro using Tapatalk

 

[904Bronco]

Does your full-size have one Doug?

Nope, not on the 79 with the 351M...

 

[jamesroney]

I would say that is correct.
I’ve never noted with any consistency, which Broncos/vehicles got the flapper valve thingy, and which did not. Seen plenty of them in my lifetime, but certainly not on every rig.

Keep in mind that the exhaust manifold for the flapper valve thingy...(Exhaust control valve) is different. One is machined flat, and uses a gasket for sealing, and the other is machined with a cone for the donut.

The engineering number for the raw casting is the same, so you can't tell them apart by reading the "part number."

If your manifold is machined flat for a spacer, then you can either run the heat riser valve, or a dummy spacer. @abrdn419 the difference between the h pipes is that the F-5246-4B is about 1 inch shorter on the driver's side to make room for the spacer.

 

[abrdn419]

Thanks for the replies. Been busy with work finally getting back to the Bronco. Here is a pic of my drivers exhaust manifold. If I was to guess the I don't have the control valve. So I dont need the y pipe for a spacer.