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Sealing header primaries at slip-on collectors junction

General engine tech -- Drag Racing to Circle Track

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cjperformance
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Re: Sealing header primaries at slip-on collectors junction

Post by cjperformance »

BigBlocksOnTop wrote:
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!

I see, slip ons and no internal weld at all, in this case, as suggested above, weld them up. Fix it right now or with any sealer you will eventually be doing it again, AND as a small leak begins to develop it will fudge the o2 sensor numbers and before you twig to the problem may cause some tuning headaches.
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Re: Sealing header primaries at slip-on collectors junction

Post by rabbit »

how much air will suck in through these leaks anywhere past a lazy idle speed?

wouldnt the leaks seal up with exhaust gas once youre moving a bit through the pipe?
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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill »

Plenty and no time soon for a clean- burning engine. Unless fitted with a restrictive exhaust system, the negative pressure pulses at any speed and high throttle opening will ingest substantial amounts of air.
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Re: Sealing header primaries at slip-on collectors junction

Post by rabbit »

if its open piped (no exhaust past the collector) wouldnt it be much easier for the negative pressure wave to pull air back through the big ass hole at the end of the collector instead of a tiny little leak in the collector slip joint?
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Re: Sealing header primaries at slip-on collectors junction

Post by MadBill »

Yes, and it does. An O2 sensor needs to be at least 12" upstream of the collector exit to avoid sample contamination, but atmospheric pressure is waiting to be invited into the pipe only 0.060" away from the exhaust stream and a little goes a long way when you're looking for accurate results.
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Re: Sealing header primaries at slip-on collectors junction

Post by inline__engine »

blast from the past, anyone found any new whizz bang sensor safe sealers (commonly available) for the slip joint to seal them up? what sort of temp rating should said sealer be ?

this might be upto the job but no idea if sensor safe
https://xtex.com.au/deacon-770-l-liquid-sealant/
https://xtex.com.au/deacon-4011-liquid-sealant/
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Re: Sealing header primaries at slip-on collectors junction

Post by Walter R. Malik »

Orr89rocz wrote: 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.
When installing them with that as a sealer, Just be sure you have no intentions of taking them apart, again. :wink:
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Re: Sealing header primaries at slip-on collectors junction

Post by peejay »

Walter R. Malik wrote: Sat Jan 11, 2020 12:38 pm
Orr89rocz wrote: 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.
When installing them with that as a sealer, Just be sure you have no intentions of taking them apart, again. :wink:
I made that mistake on a set of 3 piece (per side!) Ford headers that snaked around the front crossmember. When it had to come apart again, it really didn't want to!

It didn't have any leaks I could find with a 3/4" heater hose as a stethoscope, with no sealant.
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