Header collector reducer fabrication question.

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The Artist formerly known as Turbo84
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Doing some more exhaust work in the future and making my own collector reducers as I'm not thrilled about how much they cost in the catalogs. (I know, I'm tight, no need to tell me.) I need to (conically) expand some 3" tubing to 3.5" to match the collector ID. Short of a bunch of cutting and welding to make these (BTDT), do muffler shops have the capability to taper expand pipe? I know they regularly expand pipe to slip over other exhaust pipes, but I'm looking for a tapered expansion. Anybody seen a shop do this?

Thanks,
Mike
 
You should weld up the 4 pipes w the "pyramid" first and then you could simply roll some sheet into a cone and cut to size. I have done that once. It is a lot of work. Last time I just bought some stainless 3.5 to 3"tapered reducers and used those. If you use mild steel it'll be a lot cheaper. DIY is nice but sometimes the PITA does not weigh up to the cost.

I hear youa bout the price, especially if you're looking at burns merge collectors.

I would try to shoot for this design though, they seem to be the most efficient.
cutaway_big.gif


Another way to go is buy some cheap SB2 headers off ebay and cut the collector off those. Sometimes there are cheap damaged ones out there, cheap way to score some collectors and pipe/bends :)
 
You should weld up the 4 pipes w the "pyramid" first and then you could simply roll some sheet into a cone and cut to size. I have done that once. It is a lot of work. Last time I just bought some stainless 3.5 to 3"tapered reducers and used those. If you use mild steel it'll be a lot cheaper. DIY is nice but sometimes the PITA does not weigh up to the cost.

I hear youa bout the price, especially if you're looking at burns merge collectors.

I would try to shoot for this design though, they seem to be the most efficient.
cutaway_big.gif


Another way to go is buy some cheap SB2 headers off ebay and cut the collector off those. Sometimes there are cheap damaged ones out there, cheap way to score some collectors and pipe/bends :)

:D + you IMPORT fees, and shipping charges.....:flash:
 
TT, sorry, I guess I wasn't clear. I'm just fabricating the pipes after the header collector. My headers have square, 4-bolt collector flanges and it's hard to find reducers to fit these headers. So, I'll be cutting out a square flange to bolt to the header, but I need to make the (conical) pipe that goes from the 3.5" collector exit to the 3" exhaust pipes.

IM001085.jpg
 
Oh you need reducers. I would simply buy some necked down pipe, it's a pita to fabricate them by rolling sheet.

If you cut off the flange, I would replace it w V band clamps, so much easier than any bolt together deal. It will never blow out gaskets.
 
A muffler shop could probably expand a tube from 3 to 3.5 but it probably wouldn't be a smooth transition. They would probably charge you $25-50 to do a couple also. I know you were not thrilled about the cost of the reducers in catalogs but you can buy a pair of nice conical reducers for probably the same as the muffler shop would charge.

http://www.jegs.com/i/Flowmaster/389/R3530/10002/-1
 
Why not change the flange on the header to a more common three bolt?

The headers are ceramic coated. I don't want to mess up the coating any more than I already have. In addition, I'd still have to put out money for new gaskets/clamps and reducer pipes anyway.

I stopped at a muffler shop yesterday and we played around expanding some 3" pipe. The guy did a nice job with his machine, but expanding the pipe from 3" OD to 3.5" ID was a bit over the capability of the machine.

I think I'll just stop at a truck shop and get some 3.5 or 4 inch pipe and take a pie slice out of it to make the transition. I'm not real happy with how quick/short the transition is with most off the shelf reducers, so I'll just make a longer set that will still fit under the car.
 
ANY sheet metal shop on the planet can roll those for you without even doing the math. Tell them the cone sizes and lengths, go around the corner for a beer and come back with some pennies left over for them.
 
Cut a bunch of slats in a short piece of 3.5" pipe. Hit the end of the slats down over the 3" pipe, and weld them closed. I did that to fit my 2.5" catalytic converter on my 2 1/4" pipe neon.
 
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