How do you weld the header tubes to a merge collector?

[Samckitt]

I mean the first one you can get all the way around, most of the way around the second tube, less on the third tube & even less on the fourth. Doesn't it leak, or am I missing something? Is there a tight enough fit that it doesnt leak when it gets hot? Fill me in please.....

[Motorcitydak]

In a typical 4 into 1 merge all 4 pipes run parallel touching each other and they all end at the same spot. You then weld a cross into the middle area, there are also bullet shaped ends that are available and are said to increase flow. You weld the seams all together then the collector slips on over that and gets welded on

http://www.carcraft.com/howto/ccrp_0803_custom_exhaust_headers/mig_welding_technique.html

[Ron Sutton]

Hi Sam,

I'm assuming you're building a set of headers & welding the formed collector to the 4 tubes. If so, you need to weld it 100% all the way around. There are 3 ways.
#1 - weld it 100% from the inside & fill the gap with mig weld filler. (not attractive)
#2 - weld some from the inside & fill the gap with mig weld filler (not attractive) ... and weld the outside seams too.
#3 - Make a piece of sheetmetal the fills the gap between the 4 tubes & weld it on ... and the 4 tubes to each other ... before the collector. Then weld the collector on from outside. (photo #1)
#3b - Make a merge tip the fills the gap between the 4 tubes & weld it on before ... and the 4 tubes to each other ... the collector. Then weld the collector on from outside. (photo #2)



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[dontlifttoshift]

Those are both right but if you have a prefabbed merge collector that slip fits over all of your primary tubes individually you really cant weld it. Tabs and bolts or tabs and springs along with some RTV.

[Samckitt]

Maybe I am naming it wrong, but what you are describing isn't what I think of a s a merge collector. What I am thinking of is what I think Donny is talking about.

Something like:

https://static1.pt-content.com/images/noimg.gif

[parsonsj]

Just friction fit. Nothing more to it than that. Some guys weld tabs to hold them together or a spring or whatever.

[SSLance]

Not unlike the 1.75" headers that sometimes have one tube that wraps around a frame rail right? It just slips into place with a tight fit and seals up?

[Ron Sutton]

Maybe I am naming it wrong, but what you are describing isn't what I think of a s a merge collector. What I am thinking of is what I think Donny is talking about.

Something like:

https://static1.pt-content.com/images/noimg.gif

Oh ! ... you have a "slip-on collector." My mistake. :hand:
I thought you were building headers with a formed collector (no tubes).

John & Donny nailed it. Just slip it on & attach with bolted tabs, springs, short welds, etc. ... and the slip fit will seal asap.

[IMPALA MAN]

There are three types of collectors that can be installed.
1. A weld on collector. This is a formed collector that is welded to the four tubes and has a "star" plug welded in the middle of all four tubes. Like you see in the first pic in the #3 post. If done correctly they can be welded and will not leak.

2. Slip on collectors.... http://www.jegs.com/images/photos/32983412352C.jpg
These are NOT always merge collectors. A standard slip in collector has four short tubes (2," long) with the star plug installed welded to a formed collector. The four short tubes are large enough to slip over the four tubes on the header. These collectors cannot be welded all the way around all four tubes on the header and will leak if you are not running open collectors (an exhaust connected after the collectors)

3.Merge Collectors. http://www.afabcorp.com/cat_images/dynatech/accessories/780-01513_hi.jpg
There are TRUE Merge Collectors and look a likes. The picture in the link is a true merge collector. A true merge collector will always have:
A. Four individual tubes that are miter cut and physically merge together. Usually they can be ordered to merge at different angles. 15 degree is pretty common.
B. An outlet welded to the four miter cut tubes that has a larger opening at the final outlet than where it meets up to the four miter cut tubes.
C. Will always be slip on
D. Like any slip style collector, it cannot be sealed and welded all the way around.
Regarding look a likes, yes they probably do perform better than a standard collector, however nothing trumps a true merge collector. The look a likes are lacking the tubes merging together at a 15 degree angle. All they are at that point is a standard formed four into one collector. Then a Merge Spike is welded in to help flow and of course make it look like a merge collector. This merge spike can be seen in the second picture in the #3 post.

The best bet if you must go with a merge collector.....SPD Exhaust has some double slip merges that seal pretty good. You may want to ask them how well. http://www.spdexhaust.com/pdfs/Temp_Pages/DSMC.pdf
Best of luck and hope this helps clear the air.