BlueStag Posted March 20, 2012 Share Posted March 20, 2012 OK, I am going to lose it. Is there no stock downpipe with flange to be had new? For a 240/260. I despair of ever getting a tight joint at my flange. Quote Link to comment Share on other sites More sharing options...
Leon Posted March 20, 2012 Share Posted March 20, 2012 I believe MSA sells new downpipes with some of their exhausts. I would call and ask, and you have the luck of being local and being able to save on shipping. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted March 20, 2012 Share Posted March 20, 2012 I would just buy some headers if I were you. You've struggled long enough with the stock exhaust lol. But I do have what I think is a New Old Stock downpipe for a 240z. It has two pipes that merge to one, and a flange that meets the manifold. It stil has a Nissan sticker on it I think so it has never been used. Just some surface rust. If interested I can send you some pictures and we can talk price and I'll get a shipping estimate to LA. Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 20, 2012 Author Share Posted March 20, 2012 I would just buy some headers if I were you. You've struggled long enough with the stock exhaust lol. But I do have what I think is a New Old Stock downpipe for a 240z. It has two pipes that merge to one, and a flange that meets the manifold. It stil has a Nissan sticker on it I think so it has never been used. Just some surface rust. If interested I can send you some pictures and we can talk price and I'll get a shipping estimate to LA. If it is a tight two in the two to one, it is original. I really don't want to spend money on a header. The engine is by no means built, and would not benefit from a tubular header. And I would experience more noise, not less. I am looking for a quiet exhaust. Yes, please, a photo. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 20, 2012 Share Posted March 20, 2012 (edited) Blue Stag's post brings me to a question on how well the factory pipes work. I've got many from various inline and V6 nissans and was wondering if anybody ever compared the ones that collect almost right away to the ones that collect about 15 inches further down. I guess my question is whether anybody has optimized the best setup using factory nissan manifolds. Edited March 20, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
Leon Posted March 20, 2012 Share Posted March 20, 2012 Blue Stag's post brings me to a question on how well the factory pipes work. I've got many from various inline and V6 nissans and was wondering if anybody ever compared the ones that collect almost right away to the ones that collect about 15 inches further down. I guess my question is whether anybody has optimized the best setup using factory nissan manifolds. There is no "best". Take a look at the exhaust sticky if you want detailed information, but if you want more low end torque then use longer primaries (collect further down) and vice versa for efficiency at higher rpm. I'm doubt there is a huge difference between the factory manifolds, but I don't have enough experience with those to verify. You can play with the 2-1 merge for minor gains at lower or higher rpm, depending on where you put the merge. Exhaust Design Sticky Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted March 20, 2012 Share Posted March 20, 2012 (edited) There she is. The sticker just shows the company who imported it. It is in good condition, no pitting. PM me if you want to talk price. When I bought my car it had headers on it so I assume that someone bought this piece planning on using it then just decided to use headers instead. I have a stock exhaust manifold too. Edited March 20, 2012 by Cannonball89 Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 20, 2012 Author Share Posted March 20, 2012 I believe MSA sells new downpipes with some of their exhausts. I would call and ask, and you have the luck of being local and being able to save on shipping. Spoke to MSA, and no, they don't sell the downpipes separately, as a condition of their manufacturer. Bummer. Cannonball has a nice looking pipe, 3000 miles distant...... Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 21, 2012 Share Posted March 21, 2012 (edited) There is no "best". Take a look at the exhaust sticky if you want detailed information, but if you want more low end torque then use longer primaries (collect further down) and vice versa for efficiency at higher rpm. I'm doubt there is a huge difference between the factory manifolds, but I don't have enough experience with those to verify. You can play with the 2-1 merge for minor gains at lower or higher rpm, depending on where you put the merge. Exhaust Design Sticky My post specifically references the many different "downpipes" where the the merge is very different between the types. I have at least 4 different types here and I did like the comparison between the different pipes. As far as the pipe diameter, length, collector diameter and shape, collector length.........the formulas have not changed that much since 1975 when I started learning this stuff. Edited March 21, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
Xnke Posted March 21, 2012 Share Posted March 21, 2012 That is not a stock downpipe, I don't think...my stocker didn't have the two donut-protrusions on the flange. Just a flat flange. Might be a part to a header, though. Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted March 21, 2012 Share Posted March 21, 2012 That is not a stock downpipe, I don't think...my stocker didn't have the two donut-protrusions on the flange. Just a flat flange. Might be a part to a header, though. Yea bluestag said that too. I don't know what it is then. I doubt its part of a header, but possible. Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 21, 2012 Author Share Posted March 21, 2012 That is not a stock downpipe, I don't think...my stocker didn't have the two donut-protrusions on the flange. Just a flat flange. Might be a part to a header, though. My stock pipe does have the pipes passing thru the flange. It just has a very short 2 to 1 compared to this one. As short as imaginable. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 21, 2012 Share Posted March 21, 2012 That's probably from a 280zx as they seem short but there really are a lot of them in differing dimensions. Quote Link to comment Share on other sites More sharing options...
Leon Posted March 21, 2012 Share Posted March 21, 2012 Spoke to MSA, and no, they don't sell the downpipes separately, as a condition of their manufacturer. Bummer. Cannonball has a nice looking pipe, 3000 miles distant...... Ah, that sucks. I was planning on asking them about that, if I ever needed a new one. That is not a stock downpipe, I don't think...my stocker didn't have the two donut-protrusions on the flange. Just a flat flange. Might be a part to a header, though. Looks stock to me, all stock downpipes I've seen have the piping sticking out from the flange. Now whether it's stock for a 240Z manifold, or 260Z, or 280Z, etc. I'm not sure. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 21, 2012 Share Posted March 21, 2012 The 280Zs and ZXs I've seen (my 76 and a 78 I had and various wrecking yard cars) have the shorter siamesed pipes, the 240Zs I've seen have the longer separated pipes. BlueStag, have you taken a good look at the manifold side? It may be too corroded to seal correctly. The head interface on my manifold was so corroded that even after a resurfacing it was a narrow sealing surface. The cast steel will corrode over time. You might be replacing the wrong part. And, assuming that your engine creates a little bit of carbon in the exhaust, where are the carbon trails at the flange and manifold surface? That will tell you where exactly the leak is happening. You might find that you have a mismatched sealing surface, and some simple re-centering would fix it. There is a some play around the bolts at that interface, that will allow the surfaces to get offset. You could put some sort of witness material on the surfaces and bolt it together to see if it's an alignment issue or a surface flatness issue. How about some pictures? Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 22, 2012 Author Share Posted March 22, 2012 The 280Zs and ZXs I've seen (my 76 and a 78 I had and various wrecking yard cars) have the shorter siamesed pipes, the 240Zs I've seen have the longer separated pipes. BlueStag, have you taken a good look at the manifold side? It may be too corroded to seal correctly. The head interface on my manifold was so corroded that even after a resurfacing it was a narrow sealing surface. The cast steel will corrode over time. You might be replacing the wrong part. And, assuming that your engine creates a little bit of carbon in the exhaust, where are the carbon trails at the flange and manifold surface? That will tell you where exactly the leak is happening. You might find that you have a mismatched sealing surface, and some simple re-centering would fix it. There is a some play around the bolts at that interface, that will allow the surfaces to get offset. You could put some sort of witness material on the surfaces and bolt it together to see if it's an alignment issue or a surface flatness issue. How about some pictures? Yes, the manifold could be beat, I suppose. I did a bit of cleaning of it while it was off the engine. I don't, really don't, want to take it off again. I am trying again tomorrow or the next day with a fresh gasket and different adhesive. I have no difficulty finding the leak, although I cannot get a camera in there to photograph it. I just start the car from absolutely cold (so that the pipes are not hot) and reach around there and find it. It is coming out directly at the block, directly away from the middle stud. Could be that I am cranking down on the middle stud too much.....I'll torque the other two a bit more than the center one. Interesting that you have seen the longer pair pipes on 240s. As I wrote, mine, which came off a 260, is very short indeed. Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 22, 2012 Share Posted March 22, 2012 Just happen to be browsing the FSMs. Here's the illustrations for 72 and 76. I'm not sure exactly what the sealing mechanism was designed to be, but I think that metal rings are supposed to do the work. The rest is just carrier and alignment material. If the rings don't have a flat good sealing surface on both sides, it will leak. Have you checked the center rings of a used gasket to see what's getting crushed (good) and what's not (bad)? Good luck with it. Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 22, 2012 Author Share Posted March 22, 2012 Just happen to be browsing the FSMs. Here's the illustrations for 72 and 76. I'm not sure exactly what the sealing mechanism was designed to be, but I think that metal rings are supposed to do the work. The rest is just carrier and alignment material. If the rings don't have a flat good sealing surface on both sides, it will leak. Have you checked the center rings of a used gasket to see what's getting crushed (good) and what's not (bad)? Good luck with it. Mine looks like the '76 one. Cannon's is like the earlier design. The gasket is the size and shape of the whole flange, with five holes. Three for the studs and two for the pipes. Indeed the gasket has steel rings around the holes that the pipes pass thru. It seems to me that the rest of the gasket should be slightly thicker than the rings, but compressible. I don't get consulted when these things get designed. Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted March 22, 2012 Share Posted March 22, 2012 Yes, the manifold could be beat, I suppose. I did a bit of cleaning of it while it was off the engine. I don't, really don't, want to take it off again. I am trying again tomorrow or the next day with a fresh gasket and different adhesive. If you really want to play with the manifold to clean it up, have a look at the home chroming kits. Clean the pipe and flange up and coat the pipe and outsides of the flange with a coating of wax, leaving just the sealing face clear, then stick it in the chrome bath and build up a layer of chrome on the face of the flange. Once it's thick enough to fill all the pits and warps, just mill it off level and it chould seal again. P.S. Nice girl. Quote Link to comment Share on other sites More sharing options...
BlueStag Posted March 22, 2012 Author Share Posted March 22, 2012 If you really want to play with the manifold to clean it up, have a look at the home chroming kits. Clean the pipe and flange up and coat the pipe and outsides of the flange with a coating of wax, leaving just the sealing face clear, then stick it in the chrome bath and build up a layer of chrome on the face of the flange. Once it's thick enough to fill all the pits and warps, just mill it off level and it chould seal again. P.S. Nice girl. She's a big stinker, but she does photograph well. Unlike her daddy. I won't be chroming. I'll replace it with a header first. Quote Link to comment Share on other sites More sharing options...
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