# Pypes 3" Street Pro for 400cui?



## 66MichiganTempestC (Feb 1, 2012)

Hi everyone,

As I'm living in Germany where the parts supply is really poor, I have the opportunity to obtain a 3" Pypes X-pipe Street Pro system for my 66 Tempest with a '73 400cui block in it. The engine has unfortunately a set of 4X-1H heads with the screw-in rocker studs (and way too big chamber cc's for decent power) with Hedman headers. In the near future I'm planning on running my #12 heads and stroking the engine to get in the right compression range.
As far as I've read, a 3" exhaust will be too big in order to get a good back pressure, but would it be enough if I put a 3" to 2.5" collector reducer after the headers and then go back with an adapter to 3" or are the exhaust gases after the headers so cold that it'll have to be 2 1/4" ? Or simply get some other mufflers with more flow restriction?
If I'm just going with the pure 3", will there be any significant disadvantage in streetability (I'm not looking after best E.T. on the quarter mile, especially not with those heads)?
The 3" System would be much cheaper than ordering a 2.5" system.


Raphael


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## geeteeohguy (Feb 2, 2008)

Sounds like you already know the answer: pay more and get better results with the 2.5" system, or pick up the 3" system and make it work for cheap. Up to you. Me, I wouldn't run a 3" system on my cars. But that's just me.....


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## tvalenti03 (Feb 16, 2014)

i have pypes street pro and race pro for my camaro in 2.5 and have a much larger engine than 400. 

the 3" i will benefit from but not you. not for a 400. 2.5 is fine.

as for muffler now the street pro is loud at idle and when you rev passed 3k it resonates bad! the baffles are welded like shit and there is no packing in it either to compensate for crappy baffle welds. so you get the ringing sound from the baffles moving. you get what you pay for with a chambered style muffler.

now race pro is a straight through design with lots of packing with a perforated tube. you may think upon looking at it that its louder but you are sadly mistaken. at idle it is very quiet compared to the street pro. passed 3k it sounds great. no resonating at all. its free flowing. you will benefit more with this one and enjoy the sound.

all in all its your decision ultimately but look at it this way. if you want to be obnoxious and have a crappy sounding loud exhaust get the street pro. 

want to compliment a nice looking car with a sweet sounding free flowing exhaust get the race pro.


do with it what you will. i just thought id share my experience with you on the pypes product ive used. i bought the whole exhaust kit with x pipe. the x will also make it more tolerable with the tones.


best of luck


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## Taxangler (Sep 10, 2013)

I am not sure what I am missing. I don't get why the 2.5" exhausts are more expensive and are expected to provide lower performance than 3" X Pypes. Admittedly, I am not much of a mechanic but am just finishing a rebuild of a 1969 400 Ram Air 3 in my '69 GTO. This is intended to be a high performance show car and will not see a race track. To this end I have installed the following parts with the view to maximizing air flow and thus HP:

	Doug’s headers with electric exhaust cutouts with 2.125” primary
tubes and 3.5” collectors
	Pypes 3” performance stainless steel X pattern muffler and exhausts 
	Edelbrock Performer RPM aluminum cylinder heads with matched
manifold ports; Intake runners 215 CC; Exhaust runners 175 CC; 
Combustion chamber 72 CC
	Valve diameter: Intake -2.110; Exhaust 1.660
	Spring pressure – 125lbs. @ 1.800
	Lunati Voodoo Camshaft; Lift @ valve intake - .504; Exhaust – 527;
Duration @ .050 Intake - .233; Exhaust - .241
	Roller rocker arm ratio – 1.5
	Edelbrock Torker II single plane intake manifold: 3500 to 8000+ RPM
	Quick Fuel 750 CFM Super Street 4 barrel carburetor; Primary jet
size - .074; Secondary jet size - .080

It would have been a lot easier and less expensive to install 2.5" exhausts. The 3" inch Pypes sound awesome. I'd appreciate any feed or thoughts.




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## BearGFR (Aug 25, 2008)

The problem with 3" systems is that they're too big for anything under about 550 hp or so. It's all about flow velocity. Too large a diameter results in a lower flow velocity and you lose the scavenging effect that comes from rapidy moving exhaust flow. It's not moving fast enough any more to help "pull" the next spent charge out of the cylinders, so now the engine has to "pump" it out. That takes energy away that could have otherwise been put to use to make torque at the crankshaft. Definitely an example of a situation where bigger is NOT better. 

Bear


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## Taxangler (Sep 10, 2013)

Got it. We'll, we were targeting that amount of HP at the fly wheel and 450 - 500 at the wheels. The dyno will tell us when the weather clears so I can take it out of the garage for a dyno tune-up.


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## tvalenti03 (Feb 16, 2014)

Pypes 3" is nice if it's the race pro turbo style muffler. My neighbor had that on his car too. Sounds good. I just don't like the whole tingy sound out of the street pro chamber style. It's a poorly made muffler. Want a chambered that's good quality get flowmaster. 

If I had the money to do it again tho I wouldn't get that kit at all. Not a fan of the x. Magma flow makes a really nice kit with a way better x and I would still get a turbo style muffler. It's low rumble at idle makes it nice for cruising and parked. Open her up passed 3k and she screams. Nice tones and packing takes care of any tingy in it. Doesn't bounce of baffles to increase noise either.


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## BearGFR (Aug 25, 2008)

Just keep in mind there's a world of difference between merely _sounding_ tough and actually _being_ tough 

A great deal of the decision depends on where your priorities lie.

Bear


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## geeteeohguy (Feb 2, 2008)

All this talk about exhaust noise made me go to youtube to re-watch the car chase scene in "Bullit'!!!!


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