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Topic: Benefit of exhaust cutouts? (Read 1181 times) previous topic - next topic

Benefit of exhaust cutouts?

I already knew about them but when I saw them on Musclecar today it got me thinking about my exhaust plans.  I'm planning a 387 stroker for my car and the software simulations show it'll make 300 horsepower and 400 ft/lbs of torque with my chosen cam and my current 570 cfm carb (the gain above 570 was negligable).  Should make for an awesome commute but 300 is a little on the low side for competition I feel so I'm wondering what sort of gain I might expect with some electrically actuated cutouts.  My most recent thoughts about the exhaust system included shorty swap headers, an H-pipe, 2 high-flow cats, maybe 2 cherry bombs, 2.25 or 2.5 piping.  If I placed the cutouts early on the H-pipe what could I expect?
1983 Thunderbird-302 HO, Holley 650 CFM 4150 DP, Weiand Stealth Intake, Dual-Snorkel Air Cleaner,  Holley Fuel Pump, Procomp HEI Distributor, B&M Holeshot 2400 Converter, Custom 2 1/4 duals with no cats and BBK shorties, Taurus Fan Conversion, FMS Grill, much more to come....


"In the future, I plan on taking more of an active role in the decisions I make" - Paris Hilton

Benefit of exhaust cutouts?

Reply #1 –
more upper hp.. less bottom end torque.

or an easy way to have side pipes and not run them all the time lol

Benefit of exhaust cutouts?

Reply #2 –
:flame: Well I figured that.  Any idea how much horsepower it would gain?  Given that they're electric I could probably open them mid-race after the torque peak.
1983 Thunderbird-302 HO, Holley 650 CFM 4150 DP, Weiand Stealth Intake, Dual-Snorkel Air Cleaner,  Holley Fuel Pump, Procomp HEI Distributor, B&M Holeshot 2400 Converter, Custom 2 1/4 duals with no cats and BBK shorties, Taurus Fan Conversion, FMS Grill, much more to come....


"In the future, I plan on taking more of an active role in the decisions I make" - Paris Hilton

Benefit of exhaust cutouts?

Reply #3 –
Generally, they arnt worth it unless you have a restrictive exhaust. You NEED backpressure for the car to make power. There is a point of too much, but you need pressure to create the scavaging effect, among other reasons. do a full 2.5" exhaust, and you wont need em.
It's Gumby's fault.

Benefit of exhaust cutouts?

Reply #4 –
my Warlock lers have them built in.I've run the car with them closed and open,and there was no difference.I have 2 1/2 inch exhaust,no cats.For a 387,I hope you get a lot more than 300 HP.
'88 Sport--T-5,MGW shifter,Trick Flow R intake,Ed Curtis cam,Trick Flow heads,Scorpion rockers,75mm Accufab t-body,3G,mini starter,Taurus fan,BBK long tube headers,O/R H-Pipe, Flowamaster Super 44's, deep and deeper Cobra R wheels, Mass Air and 24's,8.8 with 3.73's,140 mph speedo,Mach 1 chin spoiler,SN-95 springs,CHE control arms,aluminum drive shaft and a lot more..

Benefit of exhaust cutouts?

Reply #5 –
Quote from: vinnietbird;123825
For a 387,I hope you get a lot more than 300 HP.

I'm just going by what Engine buttstuffyzer said.  Based on Edelbrock RPM heads and the cam I chose it makes 400 ft/lbs at 3000 rpm and 312 horsepower at 4500 rpm with open exhaust.  Ofcourse the program doesn't account for the design of the heads so it could be higher.
1983 Thunderbird-302 HO, Holley 650 CFM 4150 DP, Weiand Stealth Intake, Dual-Snorkel Air Cleaner,  Holley Fuel Pump, Procomp HEI Distributor, B&M Holeshot 2400 Converter, Custom 2 1/4 duals with no cats and BBK shorties, Taurus Fan Conversion, FMS Grill, much more to come....


"In the future, I plan on taking more of an active role in the decisions I make" - Paris Hilton

Benefit of exhaust cutouts?

Reply #6 –
Quote from: vinnietbird;123825
my Warlock lers have them built in.I've run the car with them closed and open,and there was no difference.I have 2 1/2 inch exhaust,no cats.For a 387,I hope you get a lot more than 300 HP.

Really? I had those same lers and I could definitely tell the difference. I had NO low-end torque. lol. And it was loud as !
2005 Subaru WRX STi|daily driver

Benefit of exhaust cutouts?

Reply #7 –
I like those lers better when they're capped and not so loud.
'88 Sport--T-5,MGW shifter,Trick Flow R intake,Ed Curtis cam,Trick Flow heads,Scorpion rockers,75mm Accufab t-body,3G,mini starter,Taurus fan,BBK long tube headers,O/R H-Pipe, Flowamaster Super 44's, deep and deeper Cobra R wheels, Mass Air and 24's,8.8 with 3.73's,140 mph speedo,Mach 1 chin spoiler,SN-95 springs,CHE control arms,aluminum drive shaft and a lot more..

Benefit of exhaust cutouts?

Reply #8 –
I am planning on doing that but my reason was so that I can be quite when I want and be loud when I want to be loud.  I live amongst retired folks and don't want to start up a loud car every morning and risk waking up the neigbors.  I just need to find a good ler shop near me that knows how to listen and not catch my car on fire.  The elecronic was a litte pricey for me so I was thinking of doing the cable ones.  I did see the show too.  It is a cool concept.      Jason.