Harmon Exhaust Manifolds on Ford 460 info?

[Mighty Thor]

On my 460 I have a set of aluminum exhaust manifolds that have the snails mounted above the middle of the manifold and not at the end like some I have seen. These have both been welded at one time or another and I believe that I have one side leaking still cause I am getting water in the exhaust ports and some water leaking past an exhaust gasket.
I was told that these were made by Harmon Marine but I haven't found any name on them yet. I suspect that I am going to have to replace at least one and maybe both. the Snail is bolted to the top of the manifold. so, first question.
1. How do you leak test these things? I put pressure to the engine with the manifolds off the engine and I am 90% sure that the water is not getting into the exhaust ports due to any engine cracks or gaskets. Also no indication of significant water in the oil.
2. where would you find a single or pair of manifolds like these for sale?
3. How come I wasn't smart enough to take pictures before I started asking questions? :hammerhea

[Oldsquirt]

Take the manifolds to a machine shop. They should be able to pressure test them on the same equipment used to PC heads.
Might try looking for parts atHarman Marine (http://www.harmanmarine.com/). If not there, try RexMarine (http://www.rexmar.com) or CP Performance (http://www.cpperformance.com)

[1978 Rogers]

So the sail is in the center, on top of the manifolds? If its cost much to fix, you might want to try and pick up a set. I just saw a pair on Ebay just like mine. There great and I've never had any problem.
http://www2.***boat.com/image_center/data/500/2160ChrisBoat3.jpg

[Jetmugg]

I don't have a pic to post, but it sounds like you might be talking about center riser exhaust?
SteveM

[1978 Rogers]

I don't mean to highjack this thread, but since were on the subject. What is the height of exhaust passage inside my snails? I imagine I should be careful not to over load & have water come over the hump in the snail.

[mgar_red]

Steve, that is correct.
Thor, you might be able to pull the center riser off and make a block-off plate and gasket to isolate the water jacket. If yours are like these ones, with a threaded boss at front and rear, you can plug one and thread the other with an air chuck nipple. Slowly regulate your air supply up while listening for leaks. Or better yet, fill the exhaust ports with water while laying on its side and look for bubbles. I would think 20 psi would be plenty, but if someone else has done this please chime in and post a number.
http://www2.***boat.com/image_center/data/500/1176sample1.jpg
I plan to run a check on these before I put them in. This was a before and after pic to show what a little elbow grease and polish work would do.

[Digger]

I have a pair of those, and they look just like that(one polished one not). I was wondering how you plan on plumbing your water. Are you going to pre-heat through the manifolds then to the engine or pump to engine and out the tips?

[mgar_red]

I had wanted to use the same configuration as my long logs three hose ( cold to the touch ) setup, preheat and all, but these are not made that way. There is only one hose barb at the front bottom. Water enters there and is exited out the top of the center risers, all internally. The other fittings you see in the pic are petcocks for draining them, at the same level as the front barbs.
I talked with Greg Shoemaker and asked if he had ever seen any of these kind modified with bungs welded on to achieve preheat, and he said he had not. It was discussed and the consensus was to try them as they were intended, single line.

[Mighty Thor]

Steve, that is correct.
Thor, you might be able to pull the center riser off and make a block-off plate and gasket to isolate the water jacket. If yours are like these ones, with a threaded boss at front and rear, you can plug one and thread the other with an air chuck nipple. Slowly regulate your air supply up while listening for leaks. Or better yet, fill the exhaust ports with water while laying on its side and look for bubbles. I would think 20 psi would be plenty, but if someone else has done this please chime in and post a number.
http://www2.***boat.com/image_center/data/500/1176sample1.jpg
I plan to run a check on these before I put them in. This was a before and after pic to show what a little elbow grease and polish work would do.
Yep, these are exactly like mine. I will probably try to test them as you described I know they have been repaired once cause there are welds on them. Can you confirm or identify the manufacturer? I will probably start looking for another set even If mine test ok.

[mgar_red]

These were on a "Berkeley Packajet" setup. I was sent a copy of the owners manual page that had the routing diagram. I think Hardin Marine made these, but I'm not sure. I also want to say HM and Berk are under the same umbrella.
As far as the repairs you speak of, are they a single weld line, like as in a crack repair? Reason I ask is that both these have an offset square kinda weld pattern on the inside just below the risers, like 3 to 4 inches. But I think they were manufactured like that. Both are identical.

[mgar_red]

CP has these. They were listed in the '04 catalog as H.M. and sold in pairs. They now say they're out of stock.
http://www.cpperformance.com/detail.aspx?ID=6124

[Mighty Thor]

Yep, thats the welds I am talking about, but When I pulled my snails off I saw what looked like a crack running from the water passage to the stud hole so I figured it was a repair. Not so sure now.

[jtmarten]

Are you running your outlets OT or thru-hull? If thru-hull do you have flappers? Without flappers you could still be getting water pushing its way past the riser.