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X-pipe and related

715 Views 7 Replies 7 Participants Last post by  Arto65FB
Today I got the 2 1/2" mandrell bend exhaust parts I ordered. Having only worked with stock size exhaust systems previously, I was unprepared for the massive size of 2 1/2" pipes. I'm wondering if I've gone too big for a street 5.0L of approximately 340 FWHP. Even if I shoehorn these things around and over everything including my Total Control X-brace sub-connectors, am I going to have enough exhaust velocity for some decent scavanging?

I'm considering dropping down to 2 1/4" from the X-pipe back. Any opinions out there?
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No way .. Flowmaster recommends 2.25" exhaust for 300-350 cubic inch engines under 300 HP(flywheel im guessing) .. They said upgrade to 2.5" if you're on a 3-350 in.3 engine with 300HP + .. you're right on target.
Sorry I don't have an answer for you, but can someone tell me what scavanging is? I've heard about it but don't understand it.


Scavenging (how I understand it) the effect of the shape and the volume of the exhaust and the effect from the other cylinders exhaust pulses to the cylinder in question. Varies from cylinder to cylinder. Good scavenging helps sucking the exhaust from the cylinder and so making more space for fresh intake charge. A bit vague thinking, I admit.
TDC - we're running nearly the same motor combo....

When I switched from a 2" system with an H-pipe, to the new 2.5" setup with an X, I noted no "seat-of-the-pants" loss in low-end torque, and a significant mid/upper RPM gain.

I think the Tri-Y's and X-pipe provide pretty good "front-end" scavenging, and what happens after the X, isn't as important...JMHO, YMMV!! /forums/images/icons/laugh.gif

Don't sweat it, you'll be happy with the 2.5".
With the roller E cam and gear your running you seem to be on the border of which size you should use. If you plan to use the upper RPM range that your motor can run in then stay with the 2.5. But if you plan to only street driving and can afford to change then it should not hurt anything. IMHO, if you can afford to scrape new parts then you can afford to pay someone to help you install the 2.5 system. Good luck.
If your making the x-pipe and the rest of the exhaust than its not that large at all. I was suprised at how nicely the pipes fit under my 66 coupe. I do not have the x brace, but can't imagine it wouldn't clear.
Take a look:
When I will replace the exhaust I will use 2,5" pipes into mufflers and then 2,25" off muffler and over the rear axle.
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