Aluminum Exhaust Manifolds

[wewefirex2x]

1989 5.0 Chevy. Merc, Alpha 1

I am looking for the weight reduction vs. cast iron. My concern is that I boat in saltwater with a trailered boat and the boat is raw water cooled. Is there going to be problems using Aluminum other than changing anodes on the manifolds? The price is higher on the Aluminum vs. Cast Iron of course.

 

[Don S]

Re: Aluminum Exhaust Manifolds

They (alum) don't last very long in salt water.

 

[imported_TheMan]

Re: Aluminum Exhaust Manifolds

It may be possible to get some kind of powder coat applied to them which would then allow them to last longer in salt water.

Theres not a whole lot of metal that REALLY does hold up in salt water..

 

[Chris1956]

Re: Aluminum Exhaust Manifolds

If you plan to trailer the baot, then it is a simple manner to flush the engine. if you flush the engine each time the iron manifolds will last 20+ years.

As for the weight reduction, you will save 20 points on each manny, max. Since your motor package weighs 1200 pounds, what is the point of saving 40 pounds?

 

[wire2]

Re: Aluminum Exhaust Manifolds

.....
As for the weight reduction, you will save 20 points on each manny, max. Since your motor package weighs 1200 pounds, what is the point of saving 40 pounds?

I had OMC manis so I can't speak for Merc but mine were 55 lbs per side (with risers) so 110 lbs total. My ss headers are 32 lbs for 2.
The original spec for my 5.7 drive was 915 lbs total.

What do the alum ones weigh?

 

[wewefirex2x]

Re: Aluminum Exhaust Manifolds

The aluminum manifolds and risers weigh 56.0 pounds. Cast iron ones weigh 141.0 pounds. That would save me 85 unnecessary pounds. I would hate to spend the extra money if in the long run they (aluminum) are a pain in the rear. I have always washed the boat and flushed the engine after every use. If I decide to go aluminum I will problably start flushing with some sort of salt away, nuetra salt, something along that line.

 

[wire2]

Re: Aluminum Exhaust Manifolds

....I have always washed the boat and flushed the engine after every use. If I decide to go aluminum I will problably start flushing with some sort of salt away, nuetra salt, something along that line.

I would consider mixing a pint of 2 part epoxy primer, pour it into the water passage with the other end blocked. Block the inlet as well, turn it over several times to coat all the surfaces in there, then drain into a container and use it for the other side. Epoxy primer sticks like the proverbial $hi+ to a blanket on clean aluminum, especially a sand rough casting.
It's a chemical cure so it will harden in a semi closed area. A warm spot will speed it up.

It will keep the salt off the aluminum for a long time.

 

[HT32BSX115]

Re: Aluminum Exhaust Manifolds

If you're using aluminum manifolds in salt water, your manifolds ARE the anodes!



If you REALLY want weight reduction.....wait until you're ready to rebuild.

Build up an engine with aluminum heads, intake/ex manifolds and stainless steel risers.

Put closed cooling on it.
Bring lot'$a money to the rebuilder!


Cheers,


Rick

 

[f_inscreenname]

Re: Aluminum Exhaust Manifolds

I use GLM's (aluminum) up here in the middle of the bay and have never been happier. They have exhaust runners built in them and that is a big plus. 20lbs lighter per side (manifolds only). That equals about 10 gallons of gas. I do flush regularly but I did that with the Osco's anyway. They do come with anodes but I took them out due to they tend to rot, break off and roll around inside the manifold. Or at least that is what they did in my last $2500.00 SS header set.

 

[blh1972]

Re: Aluminum Exhaust Manifolds

i called the manufacterer and asked the same question. they said about 2 years difference in longevity between the two. cast iron lasting longer.