Where can I find a metal plenum intake?

Hello,

All those plenums are made of plastic. As far as I know there is no manufacturer makes metal intake manifold for these 3.8L engines.
I know there are some metal manifolds that summit racing sells, but I don't believe any of them are for the 3.8L.

Keep in mind that these plastic manifolds are very common on many years of GM cars.
Dorman makes an improved version of this intake manifold. But that one plastic as well.

Let me know of any questions or concerns.
Thank you.

Thanks, SQM. I can check with Summit, just to be sure they have no option, since inventories change periodically. What do you think / what have you heard about the failure / reliability rate of Dorman plenums?

Those Dorman plenums work well. I have not heard anything bad about them. Have not seen one come back due to cracking or other issues.

SQM, does a precautionary plenum replacement with the Dorman plenum seem worthwhile? Since plenums do not announce they are leaking, such problems have seemed to come out of nowhere to many Buick (and GM) owners.

Pro-active plenum replacement now, rather than later spending $800.00 to $1,000.00 to repair the engine, becomes much more attractive.

There are two plenums-- upper and lower. Because both are likely of the same plastic, are leaks possible with either plenum? If a plenum if purchased from Dorman, do you recommend both upper and lower?

Fortunately, I have had this car almost two years without major problems but have driven it little. I also am aware 245,000 miles enters a danger zone for parts failure. Already, I have replaced the battery, and worked through a VATS system lockdown (with the help of 2CarPros, Joe). Now, as the parts aftermarket for the Buick 1998 begins to fade, I am eager to pre-empt any avoidable problem. What is your recommendation? (I do not know the car's history, since the wife of the guy who sold it threw out his repair papers while cleaning house).

Possible future issues with engine--
1. water pump
2. alternator
3. accessory belt and tensioner pulley

Do others come to mind?

If I remember correctly the lower part is metal. Only issue I have seen is leaking gasket for the lower manifold. So, unless you really want to, lower one does not need to be replaced. Maybe just do the gasket to prevent it from leaking in the future.

The water pump is a common issue with these, so it will be a good preventative replacement. As for alternator you should only replace if it is bad, doing it beforehand may not have any extra benefit. Just about all electrical components falls under this.

Usually, those pulleys will start to sequel before going out.

One other common item is valve cover gasket leaking.

That is probably all the major items.

245,000 is surely high mileage, but I have seen these 3800s go well past 300,000 with basic maintenance and gasket replacements.

Thanks, SQM. That gives me more of a maintenance horizon, much appreciated. Especially your experience with the Dorman plenum.

You are welcome.
Any questions, please feel free to let me know.

SQM,

After 245,000 miles on this car (and probably for the first time, ever) do you recommend replacement of the tensioner pulley assembly (ie. both pulley and bracket, including tensioner spring) or is replacement of only the pulley, enough?
From my reading, the tensioner spring and bracket are fairly stable items, unless the spring gradually loses its ability to follow the accessory belt properly. How could I test the tensioner spring for proper tension?

The pulley or the tensioner should be replaced is there is an issue. Like the pulley is squealing or the tensioner is seized. Other than that it is not necessary to change. The pulley will start making noise if the bearing go bad. When you take the belt off, as long the tensioner exerts enough pressure on the belt it is good. There is no available specification to check the tensioner's tension. As you know they typically don't go bad.

Thanks, SQM. I do plan to keep an eye on the water pump, as you suggest.

You are welcome. Let me know if you any any further questions.
Thank you.

SQM,
Thanks for all your help during the past year or so !
Merry Christmas and Happy New Year 2024 !