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Custom Exhaust PCM 454 ?

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    Posted: March-21-2010 at 12:48am
My upper exhaust on my PCM 454 is cracked. I would like to run strait pipes any ways, and was thinking of making my stainless exhaust replace the upper portion of the factory manifold. Make a plate to match the manifold and use pre bends out the back.
My concerns are heat and dissimilar metals. Auto motive bolts stainless to cast but they are not running water through it.
What say you?
Jeff
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 7:45am
Jeff,
Running a hot exhaust through the transom? What are you going to do with the cooling water from the engine?

You are talking about the "risers" correct? I think you're better off just getting replacements or having the cracked repaired.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote connorssons Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 9:56am
It wont work, stick with original equipement and you will be boating before for you know it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BFNSport Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 10:29am
Originally posted by 8122pbrainard 8122pbrainard wrote:

Jeff,
Running a hot exhaust through the transom? What are you going to do with the cooling water from the engine?

You are talking about the "risers" correct? I think you're better off just getting replacements or having the cracked repaired.


It would be a factory replacmnet.
I will have to tear it appart and see what I missing in regards to the water flow ect. to better explain my question.
Jeff
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eric lavine Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 10:48am
I have 2 sets of center rise, bbc manifolds, excellent condition. you have to keep engine room heat to a minimum, you will start to have serious problems with heat, gasoline will start to vaporize at higher temps and the end result will be vapor locks, explosion and to the likes
"the things you own will start to own you"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BFNSport Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 10:58am
I searched google for performance exhaust
and this is exactly what Iwas thinking.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eric lavine Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 11:09am
Imco, is a well known supplier of high performance parts, but at this point it comes down to dollar per horsepower ratio and what you are trying to achieve...i would suggest hi-teks, but i wont go there.
read the HP gains wisely because these companies will claim up too" a 25% increase. which on a normal aspirated BBC if installed you probably will only notice a little more crispyness to the engine. I would imagine they want top dollars for those Imco's, but it may be worth just buying the syainless and adapt to stock manifolds if those are to pricey
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BFNSport Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 11:16am
I will not buy these they are almost twice what I paid for the boat LOL
But I dont see a issue fabing these up.Just the safety factor, heat ect..
There was post on hear some wear about straight pipes .They were on a SB and what looked like custom manifonds with custom straight pipes.Hand built by the owner I thought.
I cant find the post yet..
Jeff
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 12:11pm
Originally posted by BFNSport BFNSport wrote:

   
I will have to tear it appart and see what I missing in regards to the water flow ect. to better explain my question.
Jeff


Jeff,
Yes, you need to familiarize yourself with how the marine wet exhaust works. Both the manifold itself and the riser are water cooled by having a separate water jacket around the exhaust cavities. Water enters the actual exhaust at the tail end of the riser. You need to maintain that cooling. The "hand crafted" aftermarket manifolds do this by fabricating a water jacket around the exhaust piping.

Yes, people build their own stainless exhaust AFTER the riser.

What are you trying to accomplish?

Buy the Imco's Hi-teks or get the risers from Eric.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote BFNSport Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 1:14pm
Originally posted by 8122pbrainard 8122pbrainard wrote:

Originally posted by BFNSport BFNSport wrote:

   
I will have to tear it appart and see what I missing in regards to the water flow ect. to better explain my question.
Jeff


Jeff,
Yes, you need to familiarize yourself with how the marine wet exhaust works. Both the manifold itself and the riser are water cooled by having a separate water jacket around the exhaust cavities. Water enters the actual exhaust at the tail end of the riser. You need to maintain that cooling. The "hand crafted" aftermarket manifolds do this by building a water jacket around the exhaust piping.

Yes, people build their own stainless exhaust AFTER the riser.

What are you trying to accomplish?

Buy the Imco's Hi-teks or get the risers from Eric.


Im a machine builder by trade and enjoy building custom parts for my toys.I recently sold my rock crawler that I hand built,tube frame custom axles bla bla bla.So what Im tring to acomplish is FUN for me.I have a hard time leving stuff stock.But do realize were reliablity and headachs come into play.LOL
Depending on the cost of used manifolds and design . It could be cheaper to buy the materials and build them my self maybe...

I dont like reinventing the wheel but do like making it roll better .That being said there is more than 1 way to skin a cat.

When the glass is curing ,I will start a more detailed inspection of the motor.
Thanks Jeff
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 8122pbrainard Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 2:25pm
Jeff,
If you're handy with welding then there's no reason you can't give making the riser a try. It's certainly simpler than the manifold itself. However, prebent elbows probably won't do it. The bend radius of the larger outside pipe will be different than the inside smaller pipe.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote BFNSport Quote  Post ReplyReply Direct Link To This Post Posted: March-21-2010 at 8:40pm
Originally posted by 8122pbrainard 8122pbrainard wrote:

Jeff,
If you're handy with welding then there's no reason you can't give making the riser a try. It's certainly simpler than the manifold itself. However, prebent elbows probably won't do it. The bend radius of the larger outside pipe will be different than the inside smaller pipe.


Yea it would be tricky but doable.I think it would almost have to be done in 2 halfs then seamed.Or hydroform the inside piece and slip it into the bend.
Right now Im just stoked to be working on the boat.I need to throttle back a bit.Worst case I weld the crack or jb it to get a test drive (temp)
Jeff
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TRBenj Quote  Post ReplyReply Direct Link To This Post Posted: March-22-2010 at 6:50pm
Like Pete said, you need to understand how the water cooled exhaust works. The risers keep the exhaust gases seperate from the cooling water until the very back (to prevent reversion). If you were to build some, they would need to be double walled, and transition the water jacket from the manifold into the riser. Not an easy task- theres a reason the fancy SS risers (just the upper portion of the pic above) sell for $500+.

If you want a quick and easy way to get on the water, either buy new risers, or a new manifold/riser set. We have a good used set that we just pulled off our BFN (454) so let me know if youre interested in them. The risers are 3" and arent as long as the PCM's so they are a bit easier to fit under the motorbox. The reason theyre for sale is because we're some of the people willing to pay too many $$ per hp.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote eric lavine Quote  Post ReplyReply Direct Link To This Post Posted: March-24-2010 at 8:13am
besides, you dont start at the exhaust manifolds and work in, you start at the engine and work out. for a stock engine cast irons are more than enough
"the things you own will start to own you"
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