‘74 Stock 401 Exhaust Manifolds on ‘88 360 Engine

[Thomas792]

Posted this on another forum but didn’t really get an answer.

Question - can I bolt stock exhaust manifolds from a 1974 J10 with 401 (take offs) to a 360 engine in a 1988 Grand Wagoneer?
I know there are differences - 1) driver's exhaust is a different shape, 2) old uses 3/8 bolts and new uses 3/8 & 5/16 bolts.
Can I use a stock Y-pip or do I need a custom setup?
What else will I have to do?

I have some type of shorty headers but they are very rusted and I think they need to go.
I've read ad nauseam that the stock exhaust manifolds are actually good below 5000 rpm.
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[Srdayflyer]

quick check match up the 360 exhaust gaskets to the 401 manifolds

[tgreese]

You can bolt them up, no problem. The question: will they interfere with the driveshaft that was moved to the driver's side in 1980? My understanding - the "log" manifold (a design type) used on the drivers side from '80 on is there to accommodate the change in transfer case drop, from passenger side to driver side. I'd guess none of the standard piping will work, from either era. Maybe if you can build your own exhaust pipes, it would be ok.

Yes, I understand that the pre-80 iron manifolds are pretty good, for cast iron. They won't match tubing headers, but the difference likely won't be significant. Iron manifolds are a lot more durable; back at the dealership they ran iron manifolds on the Jeepster race cars, because they stayed together. Tubing headers are street rod / race car tech, IMO.

[Thomas792]

Yep. Everyone thinks or was told there is interference. Headers need to go so I might just be looking for a set or at least drivers side cast iron exhaust. This is a mostly stock vehicle so headers are a bit of a waste with too many issues (constant leaks).

[will e]

If you want to fix the header leaks look at 'stage 8' locking bolts. I had leak issues with my 73 Mustang 351C for YEARS with headers. Used the 'stage 8' and it solved the issue.

[Stuka]

The older y-pipe will not work at all, but you can make the older manifolds work with a custom y-pipe. Though it requires a very sharp bend right out of the manifold to then go back, and then down and under to the passenger side. Its not ideal, but it can work.

Here is the difference between the two. The top is an '80 and newer.. The bottom is an '79 and older. Do note that the exhaust flange going to the y-pipe is a different style as well.

[tgreese]

Isn't the bolt spacing, pipe diameter and number of bolts on the pipe the same for both manifolds? The earlier manifold originally used the "doughnut" composition gasket that sealed to the exhaust pipe. This doughnut has the same shape as the cast part projecting from the newer manifold, and similarly seals to the flared end of the exhaust pipe.

The composition doughnut is a maintenance headache. It routinely blows out after some time and must be replaced. Manufacturers found that the exhaust pipe would seal better steel-on-steel (or steel-on-iron) so they did away with the composition gasket and started casting the shape of the gasket into the manifold. There was an interim solution of a steel doughnut that does not blow out like the composition doughnut. Maybe still available as sintered metal - https://www.rockauto.com/en/moreinfo.ph ... 36&jsn=417

The manifold seal to the block evolved similarly. Composition gaskets were replaced by no gasket, with an iron-on-iron seal.

[Thomas792]

I'm 99.7% sure that the older exhaust used only 3/8 bolts. I'm 100% sure that the newer use a combination of 5/16 and 3/8. I've got one 5/16 bolt on the passenger side in the back that will not stay tight. Wrench had to be ground down a little to fit in the very tight clearance. Came loose one time on the way to get a safety inspection so I got rejected. Don't want headers no more on this vehicle.
So I guess I need to source "new" exhaust manifolds due to the Y-pipe issue.

[will e]

Good news is you can sell the Y pipe, they are preferred by some of the car dudes.