Don Terrill’s Speed-Talk

On a 572 inch hemi street motor in a light weight A body, is there really a substantial benefit of running an xpipe or hpipe. Headers are 2.250" full. Auto trans. 6,300 rpm redline. Fitment is the big issue. Engine makes upper 700's horsepower. Not concerned with 10-20 hp. Can get it elsewhere. Ideally, I want to run true dual exhausts with no crossover.

Dont waste your time and money== The x pipe or H pipe is foe little weak suck 289 Fords ( whatever )


JOE SHERMAN RACING

You can tune the sound quality with those pipes/cross overs if that matters to you

Thanks for the replies. Especially, Joe Sherman. Right up there with the best of em' in my book.

Agree, I've never seen the horsepower gains from X-pipes many magazine articles claim.

As previously mentioned, X-pipes and H-pipes will help a lot on sound quality if any highway miles are contemplated. I've been in many built street-strip cars where the resonance of two separate exhausts would drive you nuts in less than an hour on the highway. If you don't use some sort of crossover, definitely plan on some sort of resonator eliminator cans at the tailpipes.

I've seen more than one high-horsepower street car sold because of too much noise and too much heat. Big headers, collector mufflers and turn downs in front of the axle is a sure way to make the car uninhabitable. Reason I mention it is the last one was very similar to yours. Guy made a few bucks, got older, built the car he thought he wanted in high school. He drove it one summer. First Good Guys Show he took it to, his wife flew home and swore never to sit in it ever again. The noise of a 3,500 RPM cruise, unsilenced air filters, plus 700 horsepower of heat coming off those headers made it like a rolling blast furnace. Your results may vary.

jack vines

Why can't mufflers flow well but not be so loud? Or can they but too many folks think they want loud?

The best performing mufflers I have ever seen, the Magnaflow straight through, are also very quiet== They are soo good, I always dyno test with the Magnaflow mufflers instead of just open headers. My neighbors love my now. The mufflers do NOT have to be lowd to be very good.

JOE SHERMAN RACING

bigjoe1 wrote:The best performing mufflers I have ever seen, the Magnaflow straight through, are also very quiet== They are soo good, I always dyno test with the Magnaflow mufflers instead of just open headers. My neighbors love my now. The mufflers do NOT have to be lowd to be very good.

JOE SHERMAN RACING

X2

illfish wrote:On a 572 inch hemi street motor in a light weight A body, is there really a substantial benefit of running an xpipe or hpipe. Headers are 2.250" full. Auto trans. 6,300 rpm redline. Fitment is the big issue. Engine makes upper 700's horsepower. Not concerned with 10-20 hp. Can get it elsewhere. Ideally, I want to run true dual exhausts with no crossover.

You sort of answered it in a way, if you want a tru dual, then use one!

But, H pipe will take a lot of drone out, and will give a nicer sound if you run full tail pipes too.

The H pipe will also allow more power output thru the same diameter exhaust system, what size exhaust system do you run for your 700hp beast?

Forget X pipes,they are just a crutch for oversized chrome n' polish kit form exhausts that are way too big because a fat exhaust tips sells systems, the restrictive X pipe crutches the woefull low/mid range the crappy system would otherwise have.

Just running dual 3" pipes to spintech mufflers that have a side exit in front of the rear tire. Might throw some magnaflows inline prior to spintechs to really hush it.

illfish wrote:Just running dual 3" pipes to spintech mufflers that have a side exit in front of the rear tire. Might throw some magnaflows inline prior to spintechs to really hush it.

Only 3" on an upper 700hp engine! You will definetly benefit from a H pipe as close as possible to the ideal collector length for your combo for best resulrs or any where for that matter.
The H will help you hush it too, not a lot but will help.
But still, if you want a true seperated dual and you like the sound, keep it that way.

Per the Vizard calculations, 2 x 3" pipes are good for a max of 700 HP (with 800+ CFM mufflers)

MadBill wrote:Per the Vizard calculations, 2 x 3" pipes are good for a max of 700 HP (with 800+ CFM mufflers)

I get 733hp for dual 3.5" (seperate dual , no balance pipe/s)
(talking full exhaust system here as in aprox 12' of tube bent to the aproximate shape that would be required to fit into the average car with tailpipes going over the diff etc. The mufflers can change this somewhat for the good or bad)

& 639hp for dual 3.25"

& 533 for dual 3"

These sizes will as close as possible reflect open collector performance.
Sizes can be dropped for street application where max hp is not the issue or to help quieten things down more!

The tail pipe diameter 6-8" after the muffler can usually be reduced due to the cooler gas.
Balance pipes can increase the hp per square inch due to pipe sharing.
Based on tube with .062" wall.
Shorter systems will make more hp per sq/in (usually!) (depending on where the mufflers are in relation to collectors and or exhaust exit.

edit-- p.s. these are sized for N/A apps --

Yeah, for n/a those sizes seem good. I have way more than 700 going thru dual 3" pipes on my car but its boosted

I thought Vizard used 2.2 cfm per hp for exhaust flow, so that would mean 700hp would require 1540 cfm total or 770cfm per bank. single 3" pipe can flow 115 cfm per square inch at 28" H2O from what I read in Vizard articles. That single 3" pipe should be good to 812 cfm so more than enough for 700hp... but with long lengths there probably is more backpressure and losses involved. Not sure where that 115cfm flow factor comes from.

Then again look at some of the late model LSx guys running 400-450whp thru a single 3" catback I guess you can get some power out of a 3" pipe although that wouldnt be optimal.

Orr89rocz wrote:... but with long lengths there probably is more backpressure and losses involved. Not sure where that 115cfm flow factor comes from....

Exactly. The 115 CFM/" sq. was Vizard's flow bench finding re the flow through a one foot length of straight tubing, hence my assessment that a typical dual 3" system would ideally be used for less than the calculated 739 HP.