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Author Topic:   Open headers make more power than mufflers...

Posts: 701
Registered: Jul 2001

posted 03-18-2002 02:52 PM     Click Here to See the Profile for 65_289   Click Here to Email 65_289     Edit/Delete Message   Reply w/Quote
...Or do they? That's what this debate it about.

1965 Coupe, Tremec 3550, Steeda Tri-Ax, Cable Clutch conversion, 9" N case, 4.11's, Detroit Soft Locker, 31 spline Moser axles, Daytona pinion support,, Biondo Line Lock, Ford XB3 longblock, x303 heads, B-Cam, 9:1 comp., Tri-y headers, cut-outs, Ford Racing high-torque mini-starter, Pertronix Ignitor & Flamethrower coil, 650 double pumper, Edelbrock RPM intake, K&N air, Holley electric fuel pump & AFPR, dual 2-chamber Flowmasters, Summit 3-way fronts, Rancho 5-way rears, 5-leaf springs, Chrome Export Brace, Griffen Radiator, Comp. Eng. subs.

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Posts: 834
From: Charlotte NC usa
Registered: Apr 2001

posted 03-18-2002 03:56 PM     Click Here to See the Profile for Mpcoluv   Click Here to Email Mpcoluv     Edit/Delete Message   Reply w/Quote
Originally posted by 65_289:
...Or do they? That's what this debate it about. 6eda0&postid=1064858#post1064858

Rarely does a full exhaust make the same power much less more than open headers. If a car installs a full exhaust and picks up power, I would suspect a poorly designed open header setup (collectors too short etc...). There is an article in this months Circle Track that details "How to build a no-loss exhaust system". The X and H-pipe crossovers can give you more torque and midrange however with the exhaust still open.

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capri man

Posts: 2689
From: doerun, ga.
Registered: Nov 2000

posted 03-18-2002 04:08 PM     Click Here to See the Profile for capri man   Click Here to Email capri man     Edit/Delete Message   Reply w/Quote
i am currently running an x pipe with mufflers. if i decide to remove the mufflers, how much pipe should i leave coming out of the x?

mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.

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kid vishus

Posts: 3894
From: middle of NC
Registered: Oct 2000

posted 03-18-2002 04:12 PM     Click Here to See the Profile for kid vishus   Click Here to Email kid vishus     Edit/Delete Message   Reply w/Quote
In my opinon, if you are running a poor muffler, of course open headers will make more power. But a good muffler, will make just as much if not more average hp over the entire rpm range than open headers. DRUSA did a test on a BBC super gas motor on a dyno, they made pulls wihtout mufflers, recorded peak hp and torque, and average hp and torque over th test range (which was the same as a full power pass), then installed Borla collector mufflers and made five more pulls. The Borlas lost around 3 or 4 peak HP, but gained 5 hp average. The result with the torque was the same.

All I know for sure is, my car runs exactly the same times with or without my Borlas. The only difference is the loss of a little weight (24 lbs total), and the additon of A LOT of noise without them.

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Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 03-18-2002 05:03 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
As a rule, 100% of the time an engine will make more power with open exhaust. Only whn an engine is specificaly engineered for mufflers via cam and induction will it make more power with mufflers.

Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

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Posts: 651
From: louisville, ky, usa
Registered: Jul 2001

posted 03-18-2002 05:50 PM     Click Here to See the Profile for chips67   Click Here to Email chips67     Edit/Delete Message   Reply w/Quote
will a motor make more power with turndowns just after the muffler than full exaust going out the back or does it matter? ive got 2.5 inch pipes out the back...not mandrel bent....thinking of cutting off at muffler and going to much more noise also?

67 coupe, 650dp and rpm intake on 5.0 with afr 165 heads, 4 speed, 4.11' so far is [email protected] in 1/8 mile with 1.79 60ft. time.

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Posts: 520
From: Ont, Canada
Registered: Mar 2002

posted 03-20-2002 08:18 PM     Click Here to See the Profile for mustangboy     Edit/Delete Message   Reply w/Quote
I know my motor sure picks up with open headers.I used to cut about 3 tenths off by running open headers vs my old 2 1/4 inch system with midas turbo mufflers.Switched to 2 1/2 pipes from the headers to some new flowtech afterburner mufflers and now I only lose about .15.I still have crappy unmandrell bent 2 1/4 tail pipes that I want to replace.

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