Exhaust Diameter
 

Looking for some opinions..

My current setup:

492 CI 650ish HP
Car runs 10.28 - 10.35 @ 129 consistently through the mufflers
Shift RPM 6300
2" primary / 3.5" collector Mad Dogs
3" ID exhaust with Flowmaster Super 40s
Car does see street time

My question is, would bumping up to a 3.5" ID exhaust be worth the change?
And also, are there better muffler choices like a Pypes product?

Thanks for any insight.

-joe

Not sure about the exh. diameter; I think you are on the edge of maybe 'needing' 3&1/2 inch and I am sure some will say there would be some improvement. As to the mufflers I really like the Dynomax Ultra Flows. Not too loud at cruise but wide awake at wot!

Thanks. I'm really more interested in actual performance gains more so than sound.

I run 3.5 Dynomax Round Welded Ultraflo's, with a 3.5 mandrel bent with an X pipe on my 66. Car runs the same with open headers as it does with exhaust on it. Car is pretty quiet considering.
I think the 3.5" would help.

I've been wondering this as well. I have been planning to go 3-1/2" to the mufflers and stay with the 3" tail pipes. Thinking it was hard to get mandrel bent 3" over the rear.

I run about 4' of 3 1/2" pipe to 3 1/2" Pypes Race Pros with turn downs before the axle. No crossover or X pipe. It runs .06-.08 slower ETs in the 1/4 with the mufflers on. I have it set up to drop the mufflers quickly. When I drop the mufflers, it leaves 24" of pipe as collector extensions. Previous exhaust was 2 1/2" Flowmaster system and it killed the ET and MPH! Have you ran yours with the exhaust open?

No, I have not run it open, nor do I intend to, which, is why I'm asking the questions about pipe diameter and mufflers. I run brackets so, the car's going to run what it runs on any given day so, I don't feel the need to get every last ounce of power. Plus, being I still drive it on the street, it makes it easy to leave it as is.
So, if increasing the pipe diameter to 3.5" and find the best flowing muffler helps me, that is the path I'd like to go down.

According to the Dynomax chart that ponjohn posted here, looks like I should be running 3.5".

Thanks guys. Hoping to see a few other opinions on actual change of muffler manufacturers also.

That;s why I asked if you had ran the car with open exhaust. That would let you know what ET/MPH the car is capable of and if your current exhaust is hurting your performance. I bet it is, especially with Flowmaster mufflers (although they do sound great)

Ok, now I get it... lol.. That would give me a good baseline/comparison. So, I guess I really need to do some research on best flowing mufflers now.
Thanks

I ran open Hooker Super-Comp Headers; a Collector extension (13"? each) was mandatory for best results. 11.0 times.

You'd study your Existing Collector-headpipes for a hot zone around there. Paint line helps see the Rather than cut for open extension. Color paint , not black or white, burns the best. id suggest THAT is where you want to up-size. I went with....5" dia for 37", then into my stupid Turbo muffs and 2.5" tails. Oh but 3.5" ought be what everyone else advises.

My engine Reversion has been minimized.

Mike any video of your car with that setup?

Here is an 9 year old video with the old 433 CID engine. New engine (446) makes a good bit more power (around 100hp more) but same exhaust.

https://www.youtube.com/watch?v=AkwK...-UjYTQk0Q8gN-d

Goerlich use to make the best flowing mufflers, not sure if that's still true or not? I went with Spintech on my 3.5" oval X exhaust. My build doesn't need a 3.5" pipe system, I said I wanted a 3" system when I ordered it but the 3.5" showed up. I probably don't need a 3" system either...

Whaaat? 5 inch???

Yeap. A little bit of 2-Stroke Exhaust desigh applied, to match my Converter Stall. 9.0:1 needs all the idea applied to idle and pull well off-idle.

Not loud at all.

Ok guys,
Thanks for all the info and input. Based on this thread and some reading of my own, 3.5" looks to be a worth while change.

-joe

for mufflers, a straight through design is best for max flow. jim hand tested all kinds of mufflers in his book & the flowmasters were one of the worst flowing.

the pypes race pros & dynomax untraflos are some of the better flowing mufflers & are a straight through design. summit has them for great prices... about $60ea for race pros.

Flow characteristics of various high-performance mufflers might be interested.

You'll need Adobe Acrobat Reader to view:


http://www.exhaustsoundclips.com/cfm.pdf



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