exhaust manifold attn: topnotch

[Sandman87]

Hello all my name is Mike, I am new to the forum and happy to be here and to finally have a Fiero of my own! I've wanted one since I was a kid and have owned many Pontiac's! Charles Sewell pointed me here because I am looking for a part and I hear there is a barn full of them! I need the exhaust manifold  on the fire wall side as mine is cracked. I am doing a 3.4 swap and Charles has been extremely helpful! I know there are after market ones but they are way out of my budget unfortunately. So, I just need an O.E.M replacement, used preferably, to keep cost down as my car had a blown engine and has already cost me a lot. I had to buy a used 3.4  engine and several swap parts gaskets etc..and the interior and paint is a mess and will require considerable reconditioning as well. If anyone is selling that manifold, I live in the Cincinnati area and would need it to be shipped to me. I can pay shipping if need be. Any and all help would be greatly appreciated!

Thanks in advance ,

Mike


 

[scottb]

If you can remove the manifold I would recommend having the crack welded

[GTRS Fiero]

Agreed.  That is inexpensive, and you can find your manifold.  You should probably weld both manifolds, and remove the restrictions, while you're at it.

Hmmm.  I have 2 sets of manifolds.  I wonder where they are?

[TopNotch]

If you decide to have your manifold welded, bolt it to a flat surface (a flat hardwood board will do) to prevent warping caused by the heat of welding.
Otherwise, I will look in the barn tomorrow evening.

[Sandman87]

i thought about welding it I am just worried it will crack again  . i don't want to have to remove it again . and the engine that blew was really bad i'm worried the heads were warped and could of compromised the integrity of the steel of the manifolds.

[GTRS Fiero]

I cannot address the part about the integrity of the manifolds, but the manifold will have to be run through a machine to make the mating surface flat again.

Whatever manifold you get, it should be welded, if it has not been.  The manifolds were poorly built, and cracking is common.  A good weld job will not be a problem.

The 3.4 requires more air than the 2.8.  The intake and exhaust should be opened up to allow additional air flow.

[scottb]

As a fabricator, I can say that the metallurgy of the manifolds is fine. They will not have to milled agter welding. The flamge is thin enough that the bolts will pull it tight. If you are concerned about the flatnees get a belt for a belt . Cut the belt and attach it to a board to make a long sanding block. Run the manifold back and forth to flatten it out. Yes, it will probably crack again as it is a compromised design. Opening the decklid will allow cold water to run down on a hot manifold causing it to crack. Nature of the beast

[Sandman87]

Ill take it in today and re-weld all the seams i hope it holds up .

I have a plainer at work to flatten the surfaces .


If anyone has one id still like to acquire one just in case .




Im assuming its a mild steel correct ? I need to use the right welding rods .

[Sandman87]

thank you for all your replies .   

scott ,maybe i should fabricate some shielding to prevent this in the future   

[GTRS Fiero]

You should also weld where each of the ports connect to the logs.  You can then open up the inside with a hole saw, and clean that up with a dremel.

[Sandman87]

im going to weld every thing    wish m luck its bretty bad

[GTRS Fiero]

Yeah, it is.  Welding is not my thing, but  try to keep the inside smooth.

[Fierofool]

Several things can cause the manifold to break.  Rain, as Scott said, along with the lack of supporting springs on the lower exhaust system.  I've never seen a manifold break that severely. 

The manifolds are mild stainless steel so let your welder know that.  it will make a difference in the quality of his weld.  If the old engine was blown, I would remove one of the heads and use it as my flat plane.  Bolt the manifold back in place with all cracks closed as much as possible.  The head warps on it's surface where it contacts the block.  There's a little wiggle room for the manifolds to fit onto their studs and if there was enough head warpage to affect the manifold you would see a gap between the head and block, or if it warped sideways, it would break head bolts because they are a tight fit through the head as they pass into the block. 

On a side note, before you install your 3.4, you should remove the pipe plug that's in the trunk side head just above the #5 exhaust port if you haven't already done so.  Then remove the sensor that's in the opposite head, just above the #2 exhaust port.  Put the pipe plug in place of the sensor and install a new gauge sending unit in the trunk side head.  You can use your old 2.8 set up as a guide. 

[scottb]

Ummmmm I think that is a bit more than just cracked......It looks to me that it would have to be bolted in place to be tacked up then removed and welded. I do agree that it will have to bolted to an old head and left to cool before unbolting. I also recommend an Argon purge to keep the inside clean

[Sandman87]

yeah i swapped that plug already thanks

yeah i think is going to be safer to just replace it .. thank you topnotch for taking a look i hope you have one . again its the front header besides the fire wall.


the engine is the worst ive ever seen i bet the heads were warped there was .5 inch of sludge in the oil gallery above the cam and both heads were full of sludge and carbon deposits it also spun main and #3 & # 5 barrings  when i bought it he said it over heats and is knocking so...