Is 2.5" dual exhaust enough for 537 hp?

According the magazine articles my 393 stroker should put out around 537 with open exhaust and 1 3/4 " headers.
The current exhaust system is as follows:
2.5" duals, no cats, H pipe, straight pipes go underneath the rearend( excellent way of routing those BTW).Straight thru very free flowing swedish made 2,5" Apple Racing mufflers located between the rearend and the rear bumber.
I wonder how much power, if any, is lost in this exhaust compared to a similar 3" setup.I calculated the cross area / volume of a 3" system to be a whopping 46 % more than in a 2.5" system so the pipe diameter really matters in this regard.
Also need to take into account is the fact that the mufflers are located way back, where the gasses have cooled down and their volume is much smaller than in the beginning of the exhaust system, so also 2.5" mufflers would perhaps also do in conjunction with the 3" pipes...what do you think??

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That sounds small to me for that kind of hp.On another site a guy changed to 3 inch exhaust on a fairly mild 428 cj and got quite a good boost in power(dyno and track proven).The only way to know for sure is take it too the track and run it with the exhaust and uncorked and compare the mph.

2.5" is definitely on the small side.

I would run 3" back to a set of 3" mufflers located in FRONT of the rearend housing, then weld header collector rings to the muffler outlets.

To this flange, you could install...

1. A set of mandrel bent 2.5" tailpipes for 'family friendly' street cruising. (you just attach them to the mufflers with 3"-->2.5" header reducers)

or

2. nothing! for those times when you want to hear the engine making it's most beautiful music on the street.

or

3. The removable tailpipes will make it easier to remove the complete exhaust system if you ever want to run it 'uncorked' and at racing weight. [img]/phpBB/images/smiles/icon_wink.gif[/img]

It's an exhaust system that can be changed to suit your moods, needs and desires. [img]/phpBB/images/smiles/icon_smile.gif[/img]

Good Luck!
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N20mike, that idea sounds worth thinking! Yeah, sometimes you want different things from your car and exhaust and this would do the trick.[img]/phpBB/images/smiles/icon_smile.gif[/img]
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When I got my 302w heads flowed they worked out the ideal header and exhaust size for me as well, the engine is for a street '68 Falcon and makes 300 hp/300 ft/lbs.
headers: 1.5" for 6" from port then 15/8" to collector.
Exhaust: 2.75" into 3" mufflers (with balance pipe)(twin system)
I've ended up using 2.5" for the reason you mention (that 3" is much larger). I personally wouldn't use 3" on an engine with less than 400h.p., but if you have over 500hp, then [img]/phpBB/images/smiles/icon_eek.gif[/img] 2.5" is way too small, I know this isn't anything like your engine but might help as a comparison.....

Also I crew on a friends modified here in New Zealand (don't know if they're the same as usa mod's - like a heavy sprintcar with more engine restrictions - no front wing etc), anyway we dyno his sbc 406 at 590h.p./550ft/lbs and the best exhaust for this engine was huge headers (can't remember the exact size - might be 2&quot[img]/phpBB/images/smiles/icon_wink.gif[/img] and a dual 3.5" exhaust into open chamber type mufflers.

You NEED 3 inch pipes to get close to full power. 3 1/2 would be better, but not very practical. The idea of a set of header flanges at the rear axle, and reduced down to tame it when needed is a good idea.
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