Thread: Exhaust manifold problems as well as a few others...

Hi, so I have a 2003 pontiac grand prix se with a 3100. I purchased some larger exhaust manis from a 3.5L that were supposed to fit right on, but the front manifold's holes dont exactly align. They are off enough where I will have to either tilt it up a little and drill them out OR cut off the ends and weld on the ends from my current manifold.

By tilting upwards I mean slightly putting the manifold at an angle so the holes are closer, and hopefully with drilling larger holes I can make it work. I know the middle and far right of the three this will work, but the very far left one is going to be a bit tougher to work with as it is a little more off center. I am hoping that since the openings to the 3.5L manifold are larger, that they will still completely seal and cover the exhaust opening from the engine... Then my thought also is what do i do about the gaskets?

Now doing the welding will be a pain in the a** because I will have to make sure when I chop off the ends off both pieces they are flat and I will also have to port the opening on the actual stock ones to keep that larger manifold effect. How good of an idea is it to weld these parts together or is there a better option? I have seen a lot of sucess with cast iron welding and some not so sucessful.

AND, I was wondering if I needed to purchase a larger crossover, or if my current stock one will fit right with the new manis?

Also, that stupid bracket for the dogbone motor mount seems like a pain.. Is there a good way to get that off or will I be okay leaving it??

A lot of different problems here... I am hoping I can get some good help and soon as this project is coming up quickly..

-Logan

Welding cast iron is a pain. I did a piece of my father-in-law's wood stove grille.. The cast piece must be slowly brought up to a high temp in an oven overnight, The piece then welded, then it has to be thrown back into the oven and brought back down to normal room temp, again that takes a while. Also depends on how clean the cast iron piece is. If it's dirty, like the wood stove piece, it'll look like poop on a stick. It'll probably hold, but wont look pretty at all.

I havent seen much in the way of 3.5 exhaust mani's on a 3.1.. the ones I have seen on a grand am forum also had the 3400 with the 3500 heads bolted on, making the mani's a direct bolt on affair.

The dogbone mount, which piece are you referring to? The actual dogbone is held on by 2 bolts with 15mm head and nut. That should give you enough wiggle room to get the exhaust on. Be careful rocking the engine back though. The motor mount is filled with a grease and it will go EVERYWHERE if it explodes.

I've no idea on the crossover, sorry. If the piping is the same size and the flange matches the bolts on the manifold it should work just fine

W you do know that there is a HEADER available for the 3.1... Just sayin!
: )

*facepalm* slipped my mind...