Exhaust pipe size reco for 545/P-51 buildup - 460 Ford Forum
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post #1 of 24 (permalink) Old 07-17-2009, 04:39 PM Thread Starter
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Exhaust pipe size reco for 545/P-51 buildup

hey guys.. ok Im a little confused as to how big my exhaust system should be..

so far im leaning towards D&D headers but 2-1/8" primaries... but for the rest of the exhaust, Im not sure if I should go with a 3" or 3.5" system, exiting before the rear axle.

also, im looking into magnaflows and maybe this dynatech cone turndown to further reduce the decibles without causing backpressure.

my combo:

545 w/ about 10.5:1 comp, P-51 heads out of box, hydraulic roller cam with about .643/.635" valve lift and 253/248 @ .50 duration with a 112 LSA, 1050 dominator and edelbrock victor manifold.. also using 3.73 gear with a 28" tall tire.... the project hasnt even begun yet, but i want to plan everything out before i start... i think at the end of the project, the '85 T-bird that we're building should weight around 3300 pounds... possibly, and also making at least 680 [email protected] 6000 with about 700 ib-ft peak @ 4500


also i want to know if i should go with an H- or X-pipe... or none if not recommended... but i want something that is going to be optimal for performance but also quiet enough not to bother the neighbors... besides the fact that the exhaust pulses will probably blow up my house .... yea...


but anyways, besides knowing that most of my questions should be answered upon my own opinion, id like to hear what others may think might be the way to go ;-)
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post #2 of 24 (permalink) Old 07-17-2009, 05:19 PM
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As big as you can fit IMO
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post #3 of 24 (permalink) Old 07-19-2009, 05:26 PM Thread Starter
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??? as big as i could fit? lol
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post #4 of 24 (permalink) Old 07-19-2009, 05:34 PM
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2.25
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post #5 of 24 (permalink) Old 07-20-2009, 10:19 AM Thread Starter
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2.25" primaries... but what about the rest of the exhaust.. 3? 3.5?
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post #6 of 24 (permalink) Old 07-20-2009, 10:41 AM
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Quote:
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??? as big as i could fit? lol
As far as the balance of the exhaust system and mufflers yes
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post #7 of 24 (permalink) Old 07-20-2009, 12:01 PM
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I have crush bent 3" exhaust all the way out behinf the wheels, no H or X and running Flowtech Afterburner mufflers. The headers are 2-1/8" to 3-1/2" collectors, with reducers taking it down to 3"

The car runs one tenth slower with the exhaust connected vs. 12" collector extensions.

My conclusion is that the crush bent stuff, while not that easy on the eye, isn't hurting my times much so the flow must be sufficient.

Our combos are not that much different (you've got better heads for sure, though) so I would expect similar results in your case.

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post #8 of 24 (permalink) Old 07-29-2009, 10:43 AM
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Is this for a turbo engine ...?
That camshaft is WAY out of the ballpark; in just about ALL respects.

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post #9 of 24 (permalink) Old 07-29-2009, 12:55 PM
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3 will be quieter them 3.5 . ? i don't think you could go wrong with either one . i don't think you will feel a difference in power . if you dump it before the axles it don't matter what size you go with it won't be quiet . tailpipes will help and all mufflers work best with at least 18 inchs of pipe on the back of them .

Last edited by johnnywalker; 07-29-2009 at 01:23 PM.
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post #10 of 24 (permalink) Old 07-31-2009, 01:00 PM Thread Starter
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i didnt state that i would be running a turbo, so obviously not lol. turbo's dont need wild cams... but anyways thats a different story..

im still deciding whether or not to dump or use tail pipes... but im thinking that ill just dump the exhaust before the axle and use a set of maganflows.. and if thats not quiet enough.. maybe ill put bullets or moroso spirals after it to quiet it a little further without backpressure..


i was thinking 3.5".. but im not sure if i should just go for the 3" or not.. if i go 3" , i can just go ahead and get a universal exhaust from Jegs rather than having custom work done... but in the end, what really matters is what will be optimal for the motor..

definitely im gona run 2-1/8" headers... but maybe since im gonna be using straight through mufflers and probably dump before the axle.. i can probably just go with a 3" exhaust..


i still need to ask around about that
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post #11 of 24 (permalink) Old 07-31-2009, 01:30 PM
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I would prolly go more towards the 3in exhaust. Hot gases move faster then cool gases.
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post #12 of 24 (permalink) Old 07-31-2009, 03:10 PM
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Your collector will be 3.5" or 4" JMO but I wouldn't go any smaller than the collector size.

I used to run some of those spiral type sprint car baffles on a 428 and it was LOUD!!!



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post #13 of 24 (permalink) Old 07-31-2009, 03:58 PM Thread Starter
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well i do know that hot gases move fast than cold gases..

maybe ill just stick with 3" exhaust piping and be happy with it... and done too lol


but definitely im gonna need to use maganflows to quiet it down.. i wouldnt use just spiral mufflers.. but along with maganflows they make help make a unique tone to the exhaust..

or maybe use Pypes race pro mufflers or violators and spirals... i want something totally different than anybody else ;-)
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post #14 of 24 (permalink) Old 07-31-2009, 09:32 PM
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WILD cam??? Hardly ... it's simply that the camshaft you listed is just north of a piece of trash with that combination when used in an NA situation.

Good Luck, you'll need it.

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post #15 of 24 (permalink) Old 07-31-2009, 09:39 PM
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Another option is oval tubing...it is sort-of in the middle between a 3.0-3.5 in.
Dr. Gas website has info.

I believe a 4 inch oval is equivalent to a 3.25 in. round, as far as cfm of flow rating. They measure 2.5 in. tall and 4 inch wide.

These are the pipes I am thinking of going to on my T-Bird.

Alan Mackin

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