Moparts Tech Archive
Exhaust (header attachments)79powerwagon
From: WI USA
Registered: Nov 1999
posted 07-03-2002 10:59 PM
I got my Spitfire headers on my poly 318 in my 64 B body. They fit great around the PS box, though I need to build a motor mount shim to create a bit of air space there.
Using conventional bends, the head pipes will exit right through the steering pieces, which is no good.
The factory cast manifolds are basically nothing but small diameter pipe with 4 openings in the sides, shooting straight back, and they flow POORLY!
Can I just build a steel "box" to attach to the collectors, and shoot the exhaust pipe out the back to clear the steering arms and still have good flow?
I saw on one of the cable "Hot Rod" types of shows where someone (Flow-Master?) uses a a "box" as a resonator, but it doesn't affect flow rates.
Does this sound like a reasonable idea?
Maybe this will help
Headers are designed to scavenge the flow. Pulses from 1 cylinder create a vacuum that helps pull the gas from the next cylinder. The box will probably defeat some of the scavenging effect if the flow area is bigger then the header coming into it. If it's after the collecter probably won't matter a whole lot. The pressure drop between the 90 degree turn in the box and a piece of exhaust tubing isn't that much. I would keep the flow areas the same though, since there is a pressure drop associated with increasing diameters.
Flowmaster makes an adjustable collector that you can get up to a 90 degree bend to the rear. Not sure what the part # is. Try calling Flowmaster
a resonator box might not be a bad idea, provided the volume allows minimal pressure drop. If I remember my fluids class, any time you change dimensions, you incur a backpressure penalty. Make sure the inlet and outlet tot eh rsonator has a smooth radius, much like the radius on the top of those old velocity stacks for the mech FI. This way, you minumize the "flow separation" from the walls which effectively constricts your exhaust.
Thanks guys! This is a stock poly with the 4V and headers being the only change to it. This car is for driving, not racing. I plan on 2.25" exhaust all the way to the rear.
So that's why I'm thinking about this "box" thing...
Could you weld a sweep inside the box, to maximize the flow in the 90-degree turn?
Without the sweep I'd think you would kill the scavenging effect. Just my 2-cents
Or how about a couple of 45º miters? Not as good as a nice, sweeping, mandrel-bed, but you can get it to turn quicker while still maintaining some velocity.
Fury, straight angles may be needed instead, but I'll see what I can cram in there.
I'm almost tempted to remove the headers and turn them upside down, then run a curved piece of pipe back through where it might fit!!
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