Hi, I just bought a '95 Monte-Carlo with a 3100 engine.

After reading about the numerous lower intake manifold gasket failures, I find myself getting more then a little paranoid about it.

Are the plastic or aluminium lower intakes more prone to leaking?

I read that my year Monte-Carlo should have had the plastic composite lower intake manifold, is this correct? (I have an aluminium one)

 

AFAIK, none of the 60* V6 engines came with plastic lower intake manifolds. The 3100's and 3400's both came with aluminum lower intake manifolds, and aluminum upper intake manifolds.
The 90* V6's (the 3.8L) came with a plastic UPPER intake manifold up throught the 2005 Monte/Impala where the 2004+ grand prix got an aluminum UIM.

Or are you referring to the LIM gaskets?
At some point for the 3.8L engines, GM switched from a plastic gasket to an aluminum one.
The plastic gaskets were prone to failure, but the aluminum ones are supposed to have rectified that issue.
I'm not sure what GM did with the LIM gaskets for the 60* V6 engines, but in general the plastic gasket material was more prone to degradation which was a cause of some of the gasket failures. Therefore I would assume that an aluminum gasket would be a better option.

-Riggs.

 

Excellent, that answers my question!

Thank you,