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?
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.
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.
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.