Pulled an exhaust manifold, have a couple questions

Mid 80's RWC Crusader 270.

The fitting on the end of the manifold was knocked off while pulling the engine. I can't see an easy way to repair the manifold, so looks like it should be replaced. Agreed?

When I separated the elbow from the manifold, I found that 3 of the 4 ports were blocked by a gasket. This can't be right, can it?

Not sure about that 'nut', but the gasket blocking those holes (or not) is normal. Contrary to popular opinion, those are not water flow passages: they are simply core removal holes necessary for casting the parts.

Jeff

Assuming that your exhaust setup does not have a riser, but an elbow connected directly to the manifold, the gasket should have only one hole at the top. This allows more water to build up inside the elbow for better cooling.

As for the broken nut as you call it, I believe that is part of the manifold casting that the end drain cover bolt screws into. May as well replace both manifolds and elbows since they are raw water cooled.

fastjeff said:

Not sure about that 'nut', but the gasket blocking those holes (or not) is normal. Contrary to popular opinion, those are not water flow passages: they are simply core removal holes necessary for casting the parts.

Jeff

Click to expand...

These are definitely water flow passages. I ran some water through them in the sink to verify.

erich said:

Assuming that your exhaust setup does not have a riser, but an elbow connected directly to the manifold, the gasket should have only one hole at the top. This allows more water to build up inside the elbow for better cooling.

As for the broken nut as you call it, I believe that is part of the manifold casting that the end drain cover bolt screws into. May as well replace both manifolds and elbows since they are raw water cooled.

Click to expand...

That makes a lot of sense. I have no risers, just elbows mounted directly to the manifolds.


Turns out the 'nut' is actually a brass (or maybe bronze) insert. It has a tapered pipe thread on the OD to isolate the exhaust from the raw water, and a standard 3/8-16 thread on the ID. I drilled most of it out but after a pretty thorough online search it looks like I'm SOL on sourcing a replacement so I'll just replace the manifold. If I had more time I'd make one on my lathe. It's a shame because the manifold really is in pretty good condition. I cleaned it up and all of the passages are wide open and the corrosion is minimal.

I've attached two pictures:

1) The manifold insert drilled out (mostly)

2) The insert in the other end of the manifold for reference

Apparently the Crusader manifold design was updated at some point to omit the endcap/insert, in favor of a threaded elbow.

The water will of course flow through them, but it's not necessary that those holes be open. Their purpose is to allow the sand cores used in the molding process to get out.

Jeff

Ah ok, makes sense.

Yep, what erich said. The bottom and side holes are blocked by the gasket so the riser fills with water for cooling. Go on to Osco's site and they explain all the holes and proper gaskets for your application.