Need help replacing exhaust manifolds

[toolman4]

I am getting a new longblock for a 1999 starcraft with a 4.3l vortec. I have the one piece cast iron exhaust manifolds that are in good shape but should probably be replaced. They were not the cause of my new long block. Wow they are spendy! Did they quit making the one piece manifolds for a reason? What is a good replacement if I can't get the one piece and should it be aluminum? Where is a good place to get them?

 

[HT32BSX115]

Re: Need help replacing exhaust manifolds

Howdy, I'll make a wild guess.....OMC?


You should absolutely replace them. They have been known to be cause the cause of engine failures.


There are more conventional replacements out there.

OSCO, BARR, etc.

Google is your friend!


Regards,


Rick

 

[toolman4]

Re: Need help replacing exhaust manifolds

They are original mercruiser manifolds. Was this a bad design that they were dicontinued? Just wondering why they went to a two piece?

 

[HT32BSX115]

Re: Need help replacing exhaust manifolds

They are original mercruiser manifolds. Was this a bad design that they were dicontinued? Just wondering why they went to a two piece?

Yeah....pretty bad design. The OMC models (if you buy the original type) are a fortune!

The problem is that you cannot reliably inspect the risers for excessive corrosion. When they fail, you usually destroy the engine because the water that's inside them ends up going into the engine via an open exhaust valve(s).......and you of course don't know it.....and the engine sits for weeks ro even a season.

Then, when you try to subsequently start it, it's frozen......and the games begin!!

 

[toolman4]

Re: Need help replacing exhaust manifolds

Ok, now I get it. Yeah, mine are hard to tell. Feels like they are solid and look good from what I can see, buuuuuut I'm not going to risk the new block to test my manifolds. Thanks for the help.