Correct 289/302 exhaust manifolds??

[TnMike]

Can anyone tell me if these are correct manifolds for 289/302? It seems that the bevel on the one with studs is shallow where the donut sits. Any help appreciated. Thanks Mike

 

[jamesroney]

Can anyone tell me if these are correct manifolds for 289/302? It seems that the bevel on the one with studs is shallow where the donut sits. Any help appreciated. Thanks Mike

Those are the correct manifolds for a 302 in a 1976 Ford.

That particular exhaust manifold is looking for a cast iron spacer with a thermostatic or vacuum actuated flapper inside, about 2 inches thick with a flat flange gasket on one side, and a donut taper on the other. (That's why the studs are so long.) You can certainly machine a bevel into the manifold casting, and install shorter studs, or you can find a manifold that is already machined.

When you do an internet search on "heat riser" you will see the device. Don't confuse the heat riser with the warm air intake tube. Many people call the exhaust shield tube that connects to the air cleaner snorkel the heat riser. It is not.

You might be able to find a heat riser delete block that fits as well that is a solid chunk of iron without the flapper.

 

[TnMike]

Thank you!

 

[Ovalis]

Broncos used the same exhaust block off from 73-77. 73-74 were spring activated & 75-77 were vacuum operated.

 

[jamesroney]

Broncos used the same exhaust block off from 73-77. 73-74 were spring activated & 75-77 were vacuum operated.

Thanks! I didn't know that all of the 73+ Broncos used the heat riser. @TnMike I will edit my post.

 

[DirtDonk]

If it started in ‘73 it might be another data point to add to Viperwolf1’s “P’s & Q’s“ thread.
I remember seeing them on Broncos, but I don’t remember seeing them on every 73 to 77 I ever fiddled around with.
I was thinking it was more of a 74 to 76 thing, until Ovalis added that information.
Be interesting to see what members here, who still have their stock manifolds, can add to that. Maybe there were also variations based on jurisdiction.

 

[1marteck]

I removed the vacuum heat riser from my 75 Sport. The manifold was then ground for a donut with new studs.