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the 'Duracell Project'
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there is no place for a 180° bend on any exhaust system, the ideal exhaust is a straight pipe with minimal resistance and backpressure. diy kits give you 180° bends to cut into useful bends. a 180° can be cut into a 90° and 2- 45° bends to get over the axle on most cars, with a little straight pipe and clocking of the fittings that's all it takes to get over the axle.

you can make this shape with a 180° bend, but by having the 45° loose, you can aim them to align with your system



fyi, they also make 360° bends. again no useful place in any exhaust system for a 360° bend

 

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Discussion Starter · #3 ·
thats what i was thinking.. will have to cut and use my expander to make em - no worries thanks for the confirmation :) can put my new to me multimatic to work at last :)

Who else has ever welded an o2 bung in the WORST possible location by not paying attention? (bright moment for sure)
 

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Minimum radius recommended is tube diameter times 2. In this case 3 to 5 times diameter is more desirable if you have the space.

Keep in mind a live rear axle moves in an arc, not straight up and down so the bottom needs to be wider than the peak radius, this alone helps reduce flow impedance of the bends. So from a clearance and flow standpoint your bend in the picture would be better accomplished with a series of 45 bends rather than a few 90’s.

Arriving under the rear bumper for the outlets is a low pressure area created by the vehicles forward movement through the atmosphere. This does a lot to minimize the resistances found inside the exhaust system. This low pressure area only grows in intensity with vehicle speed. If you dump underneath or out the side then you need some wind tunnel time to insure the passing air stream is not applying pressure against the exhaust flow.

Bogie
 

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When I used to bend custom exhaust my favorite way to do the tailpipes was a 45 degree bend right after the muffler in front of the rear axle then a 90 degree right above the axle. If the customer didn't want the tailpipes to exit all the way to the rear bumper then these 2 bends rotated just right would perfectly dump right behind the rear tire ( like the factory exhaust on a early 70s Chevy Nova). Sometime just an additional slight little kicker (bend) was needed to get it to the outside of the car. This was my favorite way to bend the tailpipes and seemed to be the least restrictive.
 

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the 'Duracell Project'
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thats what i was thinking.. will have to cut and use my expander to make em - no worries thanks for the confirmation :) can put my new to me multimatic to work at last :)

Who else has ever welded an 02 bung in the WORST possible location by not paying attention? (bright moment for sure)
if you can weld anywhere near decent don't use the expander. just butt weld the cut pipe and fittings.
we use masking tape for the first fit up, then peal it back for tack welds
we do a lot of custom exhaust, each custom job is cut and welded similar to what your doing
sometimes we can bend a couple and it works, but most is cut and fit as you go

a chop saw works the best for cutting tube and fittings, but you can use a grinder with a cutoff wheel
you can use thin masking tape, wrap around the tube or fitting and then mark with a sharpie when it looks good

on production aftermarket exhausts we initially start out with cut and fit, then progress to bend and try it
it typically takes 3 or 4 tries to get it right, then we build a fixture and explicit instruction for repeatability
we bought a cnc plasma table with a rotary 4th axis for H pipes and o2 bung holes
we currently have 150 fixtures hanging in the shop for all sorts of vehicles, our bread and butter is new muscle cars

bungmaster 2000. our typical exhaust has four 02 bungs for stock and wide band


H pipes, some have a welded H in there, some have a slip joint. boxing and packing determine the method
this is a slip joint, double tube cope. we run water thru the chuck into the tube, keeps slag from sticking in the tube

 

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Discussion Starter · #7 ·
i just ordered prefabbed ones for my car- the mission to cut weld and muck about is not sth i have time for now- i do have a seriously awesome chopsaw (hercules from harbor freight) and a miller setup.. did my header collectors just fine but those bends are super whacky- just too time consuming - they should arrive in the nest 2 days with my matching dynomax ultra flo mufflers - last thing i need till i can run the darn motor and tune it without ear protection ~

I have a near complete self weld kit ill hang onto for the motor home, mustang 393 or one of the other projects down the road :)
 
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