2003 grand prix gt 3.8 not supercharged

[motorhead556]

Hello and I apologies if this topic is already up here i did search but could come up with anything. I Need to buy new upper/plenum and lower intake manifold. I have some small cracks in my lower intake and i might as well change the plenum while im at it. Ive got someone who has a 2006 3.8 and will sell me the upper/plenum and lower intake manifold for a good deal. My Question is will the 2006 upper/plenum and lower intake manifold fit on my 2003 3.8? thank you for your time.

[WarStryker13]

It'll fit, but you'll need a throttle body adapter. They run about $50-$75, and you'll have to do some modification to the 06 upper intake for the evap and PCV.

[Fivefingerdeathpunch]

Could you do it, yes but it does require you to do more than just swap parts over.

You'll have to buy a throttle body adapter plate because the TB bolt patterns are different, you'll have to drill and tap the TB for the PCV system because the L36 manifold uses a different system than the L26 manifold. I'm not sure if the L36 fuel rail clears the L26 intake and you can't use the L26 rail because it's a returnless system. There are several threads on the topic of UIM swaps with most of the answers you need.

To me it's easier to just buy new lower intake gaskets and grab a new L36 upper intake manifold for like 80-100 bucks or whatever they sell for now. That is if you think your UIM is in bad shape.

[motorhead556]

Thanks for the responds. Ill just go to oreillys in town and get the lower intake manifold and the gaskets. I bought the car and found out about the leak later on. Its the actual lower intake that has 3 small cracks in it. not the gaskets.

[FordMan77]

Where are these cracks in the LIM? I don't think I've ever seen one crack from normal installs. I guess it could if someone overtorqued the bolts.

Honestly I'd just find any 97-03 GT in a junkyard and grab one there. Would save some money. Then just need the updated metal LIM gaskets and a new UIM and away you go. Don't forget to get injector O-rings as well as they should be replaced when you remove the rail.

[J7319M]

Do not buy the Chinese made Dorman lower intake manifold. There's a guy on YouTube that tried one and the angle does not match the angle of the heads. He had a massive leak. Get one from the salvage yard. Inspect the gasket surface next to the coolant passages for corrosion. Just make sure the surface is flat and not eaten away by corrosion. Get the ATP Graywerks 106001 upper intake manifold and the Fel-Pro MS95812 lower intake gasket kit. I've used both of those on my Buick and they're excellent quality.

You'll have to pull the old EGR pipe out of the lower intake by locking vise-grips on there and tapping on the vise-grips with a hammer. The ATP kit has the new EGR pipe. You'll press it in by hammering on a socket that's just big enough to go over the pipe. Get a tube of Permatex Ultra Black for the corners where the lower intake gaskets meet the end seals. Put on one heavy 1/2 inch diameter beed across there like if you were putting a bead of toothpaste on your toothbrush. Squeeze it on there and don't touch it. You'll do that for each of the four corners.