later metal upper intake manifold compatibility w/earlier 3800s

[worb4me]

Can a 1998 Grand Prix GT or whatever w/a 3800 series II take a replacement aluminum plenum from a 2004 or later GP? Don't make me go picking up tin cans so I have to cast my own ( and I'm not kidding ).

[worb4me]

OK comparing pictures it doesn't look like it, not without modifying the part.

 

And the reality is you could pull the old one off and use it as a pattern for an aluminum sand casting reproduction. True the bottom surface on piece of plate glass covered with sandpaper. Like they do with cylinder heads when machining isn't possible orbfor whatever reason. I just can't see driving a ticking bomb around ( that is once I get the other issues resolved ).

 

Edit: here I am talking back and forth to myself lol. The same ATP part number is offered for 1998 and 2004 models. Why a 2004 owner would replace theira with plastic is beyond me.

[Padgett]

What about the earlier 91-94 L-27, also metal.

[worb4me]

Not sure which cars you're talking about. A quick scan on rock doesn't show any Pontiac, Buick, or Chevy 3.8 replacements made of metal.

[rich_e777]

That's the series 1 3800, found on some of the larger GM early 90`s cars like the Bonneville and Park Avenue.

[ron350]

Yes the late model aluminum upper intake will bolt on your 1998 L36 motor but there are so many other differences that it is not a realistic option.

 

The L27 motor was a different animal and the upper intake will not bolt up to a L36.

[Imp558]

I thought the blocks and heads were fundamentally the same and we could do the lower intake manifold to get the upper that matched it, or is that wrong? Isn't that what the turbo guys do, a 1st get mani to get the aluminium?

 

And why do you want to do this out of curiosity?

[worb4me]

The plastic manifolds are unreliable. Metal ones seem to be the only way to avoid notorious problems. It seems not to be a matter of if you're engine will be flooded w/coolant, just when, that is if you stick w/plastic.

 

Well I looked again, and not to be combative, and yes they do look different, but for both 1998 and 2004 GP GT 3800 non supercharged models the ATP plastic replacement plenum is the exact same part. Just funny. What do I know.

 

And I haven't seen metal replacments (on rockauto anyway) for any 1994 Chevys, Buicks, or Pontiacs. So I'm lost once again.

[worb4me]

Yes the late model aluminum upper intake will bolt on your 1998 L36 motor but there are so many other differences that it is not a realistic option.

 

The L27 motor was a different animal and the upper intake will not bolt up to a L36.

 

 Ah man. You all are killing me! LOL. Will it bolt on or not? I can accept that there are differences, but you're making me so confuzzed!

[Imp558]

Plastic upper intakes last a predictable 80,000 miles. If you put one on now it will likely outlive the rest of the engine.

If you were looking to turbo you'd be on to something though.

[mfewtrail]

Be aware the plastic aftermarket intakes(dorman) address the issues the factory ones had. With a bit of searching you can find actual specifications on the differences between them.

[worb4me]

If you go on car complaints you'd get the impression the design is just flawed and replacing w/another plastic plenum wouldn't solve the problem (for long). Maybe I read through the comments too fast. But I remember someone on here saying it's going to leak again even after you replace it.

 

Ok, so you all aren't up to see a fellow forum member cast their own aluminum intake. I have to confess, though a hobby of mine, a very much dormant one - I've gone as far as to construct a basic foundry furnace, just really never used it. Melting aluminum isn't a big deal at all. You can do it with charcoal, or an electric heating coil. It's high time I actually did some, and this makes a perfect excuse. But it may just be easier to buy one for now. Party poopers.

 

This is a good pretty fuel efficient engine. It's only got ~127k on it. Another 80k would bring it up around 200k. No marvel for a GM. 300k or more takes babying. Of course I haven't driven this particular one very far. But if you can get a car cheap and hold onto it basically forever, why not I ask. Even to just keep it around for a family member. And it's pretty darn comfortable even for my XXlarge fat ass.

[Imp558]

If it's got 127K on it then you probably don't have a factory UIM.

[Padgett]

Thought there was a metal coolant passage kit for the plastic manifolds.

 

The series 1 and series II are slightly different mainly in the passages AFAIR you could modify the intake manifold gaskets to block the coolant passages and it would work (old time racer's trick).

[Imp558]

There's a trick involving 2 dimes to block the TB coolant ports. The metal coolant elbows are a thing, but they press into the front of the lower intake mani and connect to the alternator bracket/tensioner conglomeration thing to carry coolant towards the heater core.

[mfewtrail]

Car complaints can be taken with a grain of salt. The amount of stuff I see people complaining about that are non-issues or caused by themselves is ridiculous on any place where the general public can post about car repair. The dorman intakes have been around forever and they literally have millions of them in service right now. They made several revisions in the early days so don't judge an issue someone had in 2005 on what you might expect from an intake from them manufactured more recently. I've installed several and had zero issues with any of them. On the flip side I've witnessed factory intakes leaking with even low miles on them.

[worb4me]

Yeah there is a lot of gibberish on CCS granted.

 

I believe I looked at the date in the circle on the plenum and it struck me as original.

 

I think coolant is bubbling from underneath my front valve cover. And my radiator is leaky. I'm sore tempted to buy all the gaskets including the heads and just be done with it. But before that (ducking) I'm dumping some Barr's Block Seal just to see what happens. Not as a permanent fix, just to see if the cars temp behaves at that point. I guess theres no real mysteries though, if it's overheating something's either clogged or gaskets are shot. It's just a lot of work for an unknown vehicle, would just rather know where I stand before getting into it all.

[Imp558]

L36 engines are not difficult to find or expensive. for about the same amount of money as doing all the gaskets and a little bit more labor you could just swap it

[ron350]

If you are really worried about the 3800II upper plastic intake manifold leaking then seal the two (2) coolant holes in the lower aluminum manifold.

 

The two coolant holes can be sealed with over sized 1/8-pipe thread plugs or by aluminum welding the holes shut. The two holes in the lower manifold measure about  .400 inches in diameter and most 1/8 pipe plugs will fall through the hole so you would have to find some over sized plugs.

[worb4me]

In NJ even crap engines are prohibitively expensive.One of the btheig reasons to get this thing running into be able to get out to PA wherenyou can get parts dirt cheap.

[mfewtrail]

If you still have an interest in the series 3 aluminum intake, see this: http://www.impalaforums.com/diy-do-it-yourself-how-to/247685-l26-intake-swap-on-an-l36-engine.html

[LumiLTZ]

If you are really worried about the 3800II upper plastic intake manifold leaking then seal the two (2) coolant holes in the lower aluminum manifold.

 

The two coolant holes can be sealed with over sized 1/8-pipe thread plugs or by aluminum welding the holes shut. The two holes in the lower manifold measure about .400 inches in diameter and most 1/8 pipe plugs will fall through the hole so you would have to find some over sized plugs.

Did this with both of my L36 Luminas. With the intake off the car for LIM gasket replacement, I drilled the holes out slightly and tapped them for the NPT plugs.  Also on the side of the intake where that small cover with 2 bolts is, I pulled that and cut/ground out the passage for more coolant flow. Used plenty of thread sealer when I installed the plugs and have seen no ill effects from having no coolant flow to the TB.  As for a gasket for the little coolant passage cover, the Dorman 615-207 UIM gasket kit I used (already had a known-good/non broken UIM to use) came with one surprisingly, so I used it. 

 

 

EDIT (now that I'm on the desktop and not on the phone):

 

They're actually 1/4" NPT plugs that I used.  I cannot recall the size of drill bit I used to initially drill out the holes, but I carefully used a 1/4 NPT tap to create the new threads.  The trick is to not tap too far (NPT threads are tapered).  Go a little ways, back the tap out, then try the plug.  If it doesn't seat, tap a little more, until the plugs are pretty much flush when they are tightened down.

 

Below is the best that I can come up with for a picture of what I did, this being on the red Lumina just after dropping the boneyard drivetrain in it last year.

 

[White93z34]

I've replaced a TON of those plastic intakes. I've seen em last less then 100k and I've also changed originals at 200k+. 

 

Its cheap and it lasts for at least 80-100k miles. I just do them automatically when doing intake gaskets. 

 

You could block off coolant tubes but IMO its not worth the effort. Fix and drive. Will likely outlive the car.