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Stainless Manifolds

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tony101

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Hi,
Looking at replacing cast manifold, riser's with new one piece stainless ones.My 318 has FWC and the heat exchanger has 2 raw water exits one into the manifold and another through the gearbox oil cooler into the risers, the stainless ones only have one water inlet at the manifold. Do you guy's/girls think this will be an issue? Also could anyone describe/post photo of there exhaust set up, in particular incorporating a muffler into the system? Thanks.
Tony
 
I live in Australia the difference is a little over $1000 AUS compared to cast iron....ok if they do the job. Posting on your site as there seems to be a lot more info available....
 
Twice the cost....not bad considering you will get 3x or more time out of them.

From what I understand, with cast manifolds you can get about 5 years in salt and about 10-15 years in freshwater.

I guess you are planning on owning the boat for a long time :D
 
Yeah a keeper, mariner pacer with a single 318,probably only a local boat .Five ish years on last cast manifolds, the stainless are guaranteed for 5 years. Anyone have any experience with similar? and what about the two outlets going into the front of the manifold??
 
I've had the Hi-Tek stainless headers on my small block Chrysler for seven years now. I've had to have the port side header welded twice, once at five years and once this year. Both times in the same location. The starboard side is fine. They're 304 stainless and have pencil zincs in them. I have the fresh water cooled version. The company was good to work with. The rep in America is in Arizona, around Phoenix I think. Google American Hi-Tek. The manifolds arrived from Australia in less than two weeks, and they're made to order (so your fittings, etc. are exactly how you want them). Current price is around $2400US per set. I like them and recommend them, but they are spendy. As a true equal length short tube header, they flow much better than stock manifolds. They weigh about 15 pounds each, which takes about 125 POUNDS out of the engine room! They have no gaskets to fail and mine don't seem to get filled up with gunk. They run nice and cool, but that might be just my boat, which has a very effective cooling system. They're hard to install, as bolt clearance is tight. I went to studs and nuts and it's still a pain. If you have room, ask that they leave more space between the valve cover and the headers, so that you can get to the center valve cover bolt. I plan to replace the port side manifold in the off season this year on the recommendation of my welder. They're not a panacea and they DO NOT last forever, but I don't plan to go back to cast iron as long as Hi-Tek is in business.
 
seacad,

Do you have any pics available?I looked on there site but I guess its a custom order thing.How thin is are the walls Im wondering?
 
Thanks seacad that was the kind of info I was after, it's great to get info from a n independent source.Looking at the same ones.Could you also tell me what the rest of your exhaust system is like?I have the 2 exhausts going into a fiberglass "collector box" and then one outlet out the transom, would like to try and cut out some noise with a muffler. Thanks again.
 
Greasemonkey, they're pretty thin. That's why they're so light. I'm not an expert on metal thickness but, thinking about the thickness of a spark plug gap, I'm guessing they're on the order of .030" or so. The flange is plenty thick, at least a quarter inch. They seal well. I do have pictures, but I'm typing this at work and the pictures are at home. I can get them and try to post them by this time tomorrow, or I'll just take new pictures (engine's dirty though). I've changed mine, by re-locating the outlet fitting for the fresh water side. I put it on the top instead of on the side, for access to the valve covers, and to be sure there aren't any bubbles forming. One of the nice things about 304 stainless construction is ease of repair, assuming you have a talented TIG welder available.

Tony101, my boat originally had cast iron manifolds (with the horrible swivels), with a copper 'Y' pipe, copper muffler and single 3 1/4" bronze through hull. Needless to say this all weighed a lot. The Hi-Tek headers came with about three feet of thin wall three inch stainless pipe for each side with an angle on one end. The headers have an angled outlet and putting them togeter gets the final outlet well below the risers. I got some three inch fiberglass pipe and glassed on a couple of flanges for ease of servicing. I have dual fiberglass shorty mufflers and dual three inch plastic thru-hulls with flappers on them. It's all quite a bit lighter than stock, but it has a nice throaty rumble to it. It's not that loud, just throaty. You could get a fiberglass 'Y' pipe and single full sized muffler if quiet is what you want. several companies sell the 'Y' pipes in various sizes and configuations. Fiberglass mufflers are available from West Marine and many others. It would certainly be cheaper and easier than cutting a new hole in the transom for a dual exhaust. I like the sound of a gas V8. :)
 
Thanks again seacad, yeah I think i'll try the y piece single muffler and outlet. I to like the sound my V8 makes but maybe a little less throaty at higher revs would be good! Pics would be good If you get the chance.
Cheers
 
Here's trying to send some pictures of the manifolds as they were a while ago. They're different now, the fresh water inlets are on top instead of the side on both
 

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Greasemonkey, mine actually sounds better than that, if you like a lopey cam. I had a cam custom ground for very low end torque (peak torque is 500 ft-lb @ 2500 rpm) and it idles like a muscle car on steroids. Smoothes right out when you get above 1000 rpm though. I just did a couple trips with my new prop and the cruising rpm is down to about 2800 @ 15 knots.
 
You're welcome. I can take more pics if there's something you need to see in detail.

My boat was made with single small blocks, single big blocks and twin small blocks, all Chrysler. Mine originally had a single 318 in it. Some prior owner replaced the 318 with a 360 which I got two seasons out of before it blew. Now it's a small block 410 with more torque than a stock 440. I've seen the same boat advertised for sale with new Mercruiser 454 power in it. The owner claimed a cruising speed of 18 and a top speed of 25 knots. I cruise anywhere from 15-22 knots @ 2900-3500 rpm and top out @ around 30 knots.
 
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