Moparts Tech Archive

Exhaust

Exhaust (header attachments)

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.
The shorty headers are center dumps, that point straight to the oil pan.

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

I'm talking about a box about 4"x4"x3" high attached right at the end of the collector, with a 2.25" port shooting straight backwards...
Eric
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19superbee70
New Member
Posts: 17
From: Buffalo, NY
Registered: Jun 2002
posted 07-04-2002 12:12 AM

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.
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dart4forte
Moparts Member
Posts: 1073
From: Yakima, wa
Registered: Nov 2000
posted 07-04-2002 01:09 AM

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
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whiplash
New Member
Posts: 74
From: summit, nj usa
Registered: Mar 2002
posted 07-04-2002 09:49 AM

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.
I have the flowmaster ball and socket style collectors, and I think there is only 10° rotaion on them before it gets difficult to tighten them down.
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79powerwagon
Moparts Member
Posts: 6184
From: WI USA
Registered: Nov 1999
posted 07-04-2002 12:12 PM

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.
And they call the poly a "wide block" for good reason! There is NO room to get a wrench in there to replace the headers. The engine MUST come out first.

So that's why I'm thinking about this "box" thing...

Eric
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Snooker
Moparts Member
Posts: 319
From: Fairfield CA
Registered: Feb 2002
posted 07-04-2002 02:22 PM

Could you weld a sweep inside the box, to maximize the flow in the 90-degree turn?
I can see from the photo why ya need the sharp 90-deg turn, especially since they are dumping onto the steering linkage - talk about spongy steering

Without the sweep I'd think you would kill the scavenging effect. Just my 2-cents
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Fury_Us
Moparts Member
Posts: 744
From: OKC, OK
Registered: Jan 2002
posted 07-04-2002 04:12 PM

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.
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79powerwagon
Moparts Member
Posts: 6184
From: WI USA
Registered: Nov 1999
posted 07-05-2002 08:28 PM
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The only thing that flows worse than the stock manifolds is a cork!
Snook, in my mind's-eye, the lower, front edge would actually be a radius, the rest of it would be square. The rear side would have a 2.25" pipe attached for the muffler shop to connect the rest of it.

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!!
Eric
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