vehicular
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| 01-17-2012 07:50 PM |
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I put a Boig header on my Miata over the last few weeks, and I think it's leaking at the slip fits between the primaries and the collector. The collector is too tight to fit clamps on the female slips, and it can't be welded unless I want to pull the motor every time it needs to come out.
I was leary of leaky slips anyway, so at the suggestion of teh interwebs I tried slathering Permatex 1800F copper anti seize on the slips before final assembly (a good idea, anyway), but after the first heat cycle the grease base melted and a few of the slips sprayed a little bit of the antiseize back out onto the primaries (leading me to teh conclusion that they're probably leaking).
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jere
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| 01-17-2012 10:34 PM |
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I would just expand the tube so everything is a little more snug, then use some RTV in the joints. Or if that wasn't working I would try some band clamps, maybe cut some slots in the outer tube to be pulled tight against the inner tube. |
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vehicular
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| 01-18-2012 09:30 AM |
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The gaps are under .020". Tube expanders put high spots deeper than that on tubing this thin. And there isn't room between the female slips for clamps.
I'm thinking about Hylomar Universal Blue, or a guy on another forum suggested Walker Acoustiseal/ NAPA 35959 exhaust sealant (same thing), but I don't know if I would ever be able to disassemble everything if I used either of these? |
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jere
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| 01-18-2012 12:31 PM |
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How about the cheap ones that you expand by hand to whatever size you want?
http://www.google.com/products/catalog?q=pipe+expander&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&tbm=shop&cid=10490731503907771693&sa=X&ei=lioXT9-bKojk0QHysOTSAg&ved=0CIQBEPMCMAA
As far as the exhaust sealants those should work but they would be messy. I would think you would have to take a propane torch or something to loosen the bond if you ever had to get them off.
Another idea would be to cut slots and weld on metal tabs with a hole for a bolt and then run the bolt through and tighten the tabs together with a nut and washer. |
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jere
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| 01-18-2012 12:35 PM |
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One more thing you could do is rounding the ends of the pipe off by hammering them in or out then RTVing the inside |
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sirnixalot
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| 01-18-2012 07:25 PM |
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GMCBob has a large solid steel cone shaped tool that he uses to de-oval the opening of larger exhaust pipes. Basically puts the nose of the cone down in the entrance to the pipe and thumps it with a hammer till the pipe opening is round again.
You could do something similar on a smaller scale, just get a tapered cone turned out on a lathe. You could even go so far as to get it turned where the taper evened out into a cylinder with an OD was 0.020" larger (or a gnats cock less) than the ID of the pipe. |
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vehicular
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| 01-18-2012 08:38 PM |
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The Hylomar never solidifies fully, it just jells thick enough to seal gaps. actually, the back of the tube reads like a wish list for sealants. It seals huge gaps (relatively speaking) from -400 to 600F, can be put into service imediately, seals effectively any materials, etc, etc, etc... I'm sure it gives you SARS on contact.
Obviously a 600F rating isn't enough for direct exhaust gas contact, but I'm going to try it anyway and hope they were just being conservative. If it lasts 6 months, I'll be thrilled. After that I'll try the Walker/ NAPA exhaust goo, then I'll try getting a form machined. If nothing else works, I'll have to figure something out with welding tabs onto the collector slips and making them into their own clamps. I actually thought of that before, but I'm trying to avoid having to send the collector off to get it re-coated (Boig headers are mild steel), and being without the car for 2-3 weeks for shipping, waiting in line, coating and return shipping. |
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vehicular
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| 01-18-2012 08:38 PM |
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Thanks for the help, btw. |
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jere
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| 01-19-2012 10:03 AM |
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No problem post back up how it goes. |
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vehicular
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| 01-21-2012 09:15 AM |
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Well... it's quieter. Maybe. A little.
I pulled mid pipe and rear section off and fixed about 20 irrelevant little pinholes, and maybe 2 actual exhaust leaks, went over most of the welds with the TIG, and sealed up the slips with Hylomar (which really is magical stuff; it must have asbestos and AIDS in it).
The car sounds is notably cleaner/ less raspy, and the total volume is down a touch, but not as much as I hoped it would be. I guess I was hoping to get the exhaust off and find that I missed an inch of weld some place, or something. Optimism breeds disappointment, lol. Monday I'll order a stainless Moroso Spiral Flow and see what happens. I've used the old mild steel ones before, and they worked great until the baffles rotted out. Hopefully the stainless ones are the answer, because I'm going to have a hell of a time fitting a real resonator in there. |
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kj
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| 01-21-2012 09:53 AM |
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Old Porsche 4 Cylinder cars like the 912 use a slip joint on the muffler. From Napa or other parts store there is a black goo we called "acoustic sealant". It's a bit messy but it works like a champ, just don't get it on your clothes and make sure you wear gloves because it stains... |
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vehicular
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| 01-21-2012 12:15 PM |
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That's the NAPA 35959 I mentioned. It's also sold as Walker Acoustiseal. Does it come apart when you need it to, or is it just really high temp glue? |
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kj
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| 01-23-2012 09:45 AM |
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aha "walker" that's it... it will come apart it's just a filler not really a glue... you couldn't use it to fill large gaps it would blow out but that's not what it's for.. it's for small gaps and imperfections and for those it works great |
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