Aluminum or Cast Iron Two Piece Manifolds?

[Stamey]

I have a 4.3 with the old one-piece manifolds. Trying to decide if there is an advantage to going with the aluminum manifolds from here: MercruiserV6conversionkit
I run in mostly fresh water. Every now and then I see brackish water (once or twice a year) and even less do I see salt water, and it's always stored on the trailer, with flushing if I am in brackish or worse.

I would imagine that the aluminum manifolds would last longer in the predominantly fresh water I'm in, but I need input from those who know better than me. I'm also guessing that salt water isn't a big deal with aluminum if I am flushing when I get out of it. Am I wrong here?

And if anyone has suggestion on better or cheaper manifolds for this situation, I'm all ears. I'm not afraid to put money into them if they are going to last longer but don't want get ripped off.

Also, if I were to go with used cast iron manifolds, do I need to source a special set of elbows so I don't have to buy a new Y-pipe?

Thanks,
Chris

 

[tpenfield]

Re: Aluminum or Cast Iron Two Piece Manifolds?

I believe that the aluminum manifolds are strictly for fresh water. Some exposure to salt water might be OK, but you will want to check them every few years.

I have also seen ceramic coated aluminum manifolds on the web (somewhere ?) and those might offer some longevity.

 

[NHGuy]

Re: Aluminum or Cast Iron Two Piece Manifolds?

Get the iron, aluminum is fresh water only and has a higher cost. I bought some Mercruiser V8 exhaust manifolds last summer for $160 each by phoning a company that has a big e-bay store and getting their e-bay price. I think I saved 15 or 25 each over their internet store price, and even more over their walk in price.
Since you are getting elbows too you can save some real money. BTW make sure you get the OE graphite coated gaskets for between the manifolds and elbows. The coating is shiny gray and the consistency of a crayon.
Also factor in shipping. On heavy stuff like this it can be the difference.

Ditto on ceramic if you are concerned about corrosion. I know they have ceramic coated cast iron but I don't know about the aluminum.

 

[Stamey]

Re: Aluminum or Cast Iron Two Piece Manifolds?

Thanks for the info. Now I just have to track down the best brand/deal. I understand, from another thread, that Bondo had a bad experience with the GLM brand at one time, so I guess I should be cautious with those.

Thanks,
Chris

 

[Bondo]

Re: Aluminum or Cast Iron Two Piece Manifolds?

Thanks for the info. Now I just have to track down the best brand/deal. I understand, from another thread, that Bondo had a bad experience with the GLM brand at one time, so I guess I should be cautious with those.

Thanks,
Chris

Ayuh,... I guess ya found my thread,..??

The GLMs seem to suffer from core shift, durin' the casting process...

Mine were fixed, 'n are still holdin', but I won't buy another set of 'em...