Surprise today

I was doing some cleaning around the valve covers today and noticed something I should have already with all the looking at vacuum lines I've done. My car has an aluminum intake manifold!

One aluminum manifold is GM 89018222, can be used to replace plastic. Maybe someone remembers if they were original to some 3800 factory builds or developed for service replacements for the plastics.  IDK for sure, but I think late 3800 NA factory builds used them. The 89018222 bolts onto any NA series II 3800.

Another aluminum manifold that was original was made for the RWD camaro/firebird; it pulls air from the belt side of the engine (our pulls air from the bellhousing side).

My guess is your original manifold failed. Problems with the plastic ones are legend: https://bobistheoilguy.com/forums/threads/dreaded-gm-3800-intake-manifold-gasket-problem.127958/  One general problem was that the metal EGR tube routed up through the lower metal intake manifold burns holes in the plastic upper manifold, allowing coolant to be mixed into the crankcase and cylinders. Unfortunately, the signs don’t always become obvious until the coolant contaminated engine oil destroys the engine.  I guess on yours the manifold was replaced preemptively or to fix a coolant loss mystery. These cars have hydraulic lifters, and lifter noise at the first engine start of the day can be a telltale of this condition. But, I don't really know.

Also see https://www.gmforum.com/general-gm-chat-88/dorman-upper-intake-manifold-issues-%2A%2A%2Amust-read%2A%2A%2A-231528/

G'night...

Cliff96 wrote:

My car has an aluminum intake manifold!

Pictures, please!
Recently I replaced my ruined manifold with the new one and did't like its quality.

AFAIK, all the supercharged engines have aluminum intakes.

LARRY70GS wrote:

AFAIK, all the supercharged engines have aluminum intakes.

Right - the plenum under the SC. The NA engines have plastic BUT the aftermarket came up with more durable plastic and an aluminum copy of the GM plastic, and GM came up with an aluminum manifold for FWD that they installed in factory on some lines. Firebird/Camaro had an alternative manifold for front facing engine, made of aluminum. It would fit on the FWD mounted engines but for the air snout is in the wrong place.