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Sealing header primaries at slip-on collectors junction

General engine tech -- Drag Racing to Circle Track

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BigBlocksOnTop
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Sealing header primaries at slip-on collectors junction

Post by BigBlocksOnTop » Mon Mar 05, 2012 10:46 am

I want to use a wide band 02 for tuning.Here's my problem. Flow Master 4-2-1 collectors were installed and welded on the outside where the weldor could reach. Now, the area ''inbetween'' the four tubes is not accesable for welding and probably presents an area where air can be admitted and ''fool'' the 02 sensor. How can this area be sealed up. I'm thinking of a high temp. sealant, not to thin and a vacuum source to draw it into the cracks and make a seal.Any suggestions will be a big help. Thanks.

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Re: Sealing header primaries at slip-on collectors junction

Post by Orr89rocz » Mon Mar 05, 2012 1:11 pm

Copper RTV? I've used it on my header flanges in turbo applications and its held up well.

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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill » Mon Mar 05, 2012 7:45 pm

As far as drawing whatever sealant into the joint, the pressure pulses of a running engine usually do the job pretty well. The negative pulse sucks it in, but the positive doesn't seem to blow it out.

Header flanges, because they butt up to the relatively cool head, don't present anything like the temperature challenges of a joint surrounded by EGT parts.
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Re: Sealing header primaries at slip-on collectors junction

Post by Orr89rocz » Mon Mar 05, 2012 11:26 pm

I also used it on the turbo flange itself and wastegate and it has held up too. Meant to add that earlier, not just the header flange, but the turbo flanges as well.

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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill » Tue Mar 06, 2012 1:17 pm

Hmmm... Permatex Ultra Copper RTV is factory rated to 700° F. intermittent. Typical piston engine EGT's range from 1100 to ~1400° F. for NA, several hundred more for turbo apps. Either they're really underrating their product or you're operating on borrowed time..
Felix, qui potuit rerum cognscere causas.

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Re: Sealing header primaries at slip-on collectors junction

Post by Orr89rocz » Tue Mar 06, 2012 8:21 pm

I believe is grossly underated. I have steel shim between the T4 flange and the turbo and use the permatex copper rtv on/around it for extra seal. I have a laser heat gun that has verified it has reached over 700 deg and I've even had the turbo housing glowing. I tore it down after a year and the rtv is still there sticking pretty strong. I had to shave it off with a razor and take the wire wheel to the area to clean it up. Lots of guys use this stuff for header gaskets and turbo flange gaskets. Works good as long as the surface is clean smooth and flat.

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Re: Sealing header primaries at slip-on collectors junction

Post by mbrooks » Tue Mar 06, 2012 10:28 pm

i was having the same problem. the guy who designed my car said they used grease between the slip joints to seal but don't know if they used an o2 sensor downstream, their tolerances are tighter then the person who did my exhaust would be. i tried rtv but didn't have any luck as it didn't dry well enough or seal, the stuff was actually drawn into the exhaust, maybe i didn't let it dry long enough. right now using o2 sensor in one primary only, but if i was to try it again downstream of the primaries i would consider this setup...

http://www.spdexhaust.com/pdfs/Temp_Pages/DSMC.pdf

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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill » Tue Mar 06, 2012 11:08 pm

Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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Re: Sealing header primaries at slip-on collectors junction

Post by F-BIRD'88 » Wed Mar 07, 2012 4:11 am

http://www.por15canada.com/can/puttys.asp

Fire Seal 2000

This high temp ceramic glass filler is sold by various companies.

its basicly Muffler cement. surfaces must be clean to bond. Exhaust carbon has to go. Let it dry cure first.

http://www.aremco.com/product/a15/

pyro putty

http://ecx.images-amazon.com/images/I/5 ... SS500_.jpg

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Re: Sealing header primaries at slip-on collectors junction

Post by cjperformance » Wed Mar 07, 2012 5:41 am

if the slip joint is a VERY good fit and the upstrean pipe slips inside the downstream pipe the heat/expansion will, along with some exhaust supplied corrosive moisture and carbon, seal it up fine within a very short time.
but, often in header joints the pipes are only welded, visibly, around say 2/3rd's of the pipe on a typical collector join as you cant get the welder right around the pipe for obvious reasons. BUT if you can see inside the collector you will likely see that the pipes are internally welded where the pipes lay together then slightly up each side, then the collector slips over, the welded as far around as possible but in the process is welded to the internal weld on the pipe contact points, therefore it can be perfectly sealed when it may not look like it is.
If in doubt you could pressure test them.
If you use a sealer, just be sure it is labeled as "Sensor Safe", the by products of heating some sealants will destroy an O2 sensor , so just double check.
Craig.

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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill » Wed Mar 07, 2012 8:25 am

Good points, CJ.
FWIW, a lot of racers don't understand the negative effects of poor header sealing in allowing some of the "'tune' to leak out". (Not to mention frying rocker gaskets, plug wires, the driver, etc..)
Felix, qui potuit rerum cognscere causas.

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Re: Sealing header primaries at slip-on collectors junction

Post by BigBlocksOnTop » Wed Mar 07, 2012 8:28 am

cjperformance wrote:if the slip joint is a VERY good fit and the upstrean pipe slips inside the downstream pipe the heat/expansion will, along with some exhaust supplied corrosive moisture and carbon, seal it up fine within a very short time.
but, often in header joints the pipes are only welded, visibly, around say 2/3rd's of the pipe on a typical collector join as you cant get the welder right around the pipe for obvious reasons. BUT if you can see inside the collector you will likely see that the pipes are internally welded where the pipes lay together then slightly up each side, then the collector slips over, the welded as far around as possible but in the process is welded to the internal weld on the pipe contact points, therefore it can be perfectly sealed when it may not look like it is.
If in doubt you could pressure test them.
If you use a sealer, just be sure it is labeled as "Sensor Safe", the by products of heating some sealants will destroy an O2 sensor , so just double check.

I understand about being seal welded ''internally''. My application is not. I'm using the flow master slip on 4-2-1 collectors. Like you say about the exterior welding being about 2/3's. That true in my case, but theres that area that you cannot get to to weld. I'm thinking of using a vacuum source to draw a high temp sealer in the leak. Thanks for the tip on ''sensor safe''. I'll have the hdrs off the car so I can stand them up. I have looked at some of the sealers. One is of a honey consistancy....I'll think it will work!

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Re: Sealing header primaries at slip-on collectors junction

Post by BigBlocksOnTop » Wed Mar 07, 2012 8:32 am

I want to thank every one for the tips. I think I will prevail. It's all about tuning with wide band 02's. Maybe a very slight leak is ok, but I cringe on that. It would make the carb ''fat''. Thank You.

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Re: Sealing header primaries at slip-on collectors junction

Post by turbofabricator » Fri Mar 09, 2012 11:46 am

Personally, I would cut the collectors off and weld them on the correct way. A couple of hours of work and it is then correct. Be sure to mount the O2 sensor at the 10:00-2:00 position, too. Mounting it at the 3:00-9:00 can kill it with a blast of water on start up. And adhesive used will just be a temporary band-aid Good luck with your project.
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Re: Sealing header primaries at slip-on collectors junction

Post by ProPower engines » Fri Mar 09, 2012 12:27 pm

If you are a good old school welder then just take a 3/32" 6011 stick at about 70amps DC and reach into the collector and weld away.
I have done that lots of times over the years to fix those leaks when the manufacture forgot to weld it during the building process.
Dave
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