'71 GMC 2500 exhaust manifold (350) interchange.

[BigBird05]

The only time I have seen a manifold turn cherry red was when it was run on a Dino at WOT and maximum load. That kind of sustained heat will do that to cast iron.

[W. Higgins]

Originally Posted by BigBird05

The only time I have seen a manifold turn cherry red was when it was run on a Dino at WOT and maximum load. That kind of sustained heat will do that to cast iron.

On earlier vehicles where you manually control the spark advance having the spark severely retarded will do it too, but in this case I haven't had the timing slip and when you run that heavily retarded you'll eventually see the coolant temp rise, which also hasn't ever been an issue.

[W. Higgins]

I swapped out the manifolds last night and had it running before bed. Took it out for a drive after tidying up some things this morning and it's still the same great running truck it always has been. While the manifolds were off I pulled the plugs and did a quick compression check. Everything is about 150lbs+. Timing is exactly where it's supposed to be and nothing is amiss. Thanks to everyone for helping me quickly resolve the part application issue so I could get this out of the way before the week started.

[AussieinNC]

Many thanks for the update!

The folk here love to help everyone out...

Enjoy your truck !

[W. Higgins]

I know how people like to see these old beasts still in service. This was back in the spring dragging home a new piece of iron.

[Andy4639]

Glad you got it going again. Those manifolds will blow out like that if you hit them with water after a long hard run. Are you open the hood up after a long run in the rain the rain runs off the hood down into the motor. Over time they get weak and will blow out.