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 7Likes
03-01-2015, 07:20 AM
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Senior Club Cobra Member
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Join Date: Dec 2001
Location: Shasta Lake,
CA
Cobra Make, Engine:
Posts: 26,596
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Not Ranked
I gained nearly 20 horsepower when I changed the exhaust pipes on my old cobra. Also you haven't taken into account any of the parasitic loss in the movement of engine parts and I don't know if you have air conditioning or not, but the water pump alone takes some power as does anything attached to the engine. Remember, when they run them on an engine dyno, it is with open headers, no water pimps or anything else and the only loss is what is in the engine itself. On mine my flywheel horsepower was 530 and the RWHP was 390.
Ron
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03-01-2015, 07:32 AM
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Senior Club Cobra Member
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Join Date: May 2001
Location: Florence,
AL
Cobra Make, Engine: RCR GT 40 & 1966 Fairlane 390 5 speed
Posts: 4,511
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Not Ranked
what size are the header tubes?
a motor is a air pump, cubic feet of air in and same cubic feet of air out.
When you try to make max hp/tq you need to look at your carb, air cleaner, intake, heads, headers and sidepipes. All must work together.
Everything could be matched but the air cleaner and you will lose hp/tq.
Take a look at Classic Chamber Classic Chambered Exhaust Inc. - Cobra
I bought a pair of 3" i.s. pipes that were 4" longer than the ones I have. More hp and quieter.
I have a 354 c.i. motor in my Cobra with 401 rwhp / 416 rwtq.
A 155 hp lost is a lot.
Keith Craft told me that he typical saw a 20% lost in a Cobra from engine dyno to chassis dyno for the same motor.
Part of the fun is looking for 10 more hp. 
Dwight
when they dyno motor they use air horns, largest headers, no mufflers, no alternator, electrican water pumps and other tricks to make max hp for the motors they sell.
the chassis dyno is the real story.
__________________
''Life's tough.....it's even tougher if you're stupid.'' ~ John Wayne
"Happiness Is A Belt-Fed Weapon"
life's goal should be; "to be smarter than inanimate objects"
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03-01-2015, 07:52 AM
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CC Member
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Join Date: Jan 2001
Location: Cape Coral,
FL
Cobra Make, Engine: 2009 Solbra
Posts: 3,861
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Not Ranked
Cobra Muffler Retrofit
__________________
Dan Wulff
I carry a gun because a cop is too heavy.
(No doubt, most will blame it on the donuts.)
You're just jealous because the voices only talk to me
Earth is the insane asylum for the universe.
The gene pool could use a little chlorine.
The original point and click interface was a Smith & Wesson.
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03-01-2015, 10:13 AM
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CC Member
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Join Date: Jan 2015
Cobra Make, Engine: backdraft roush 427r
Posts: 17
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Not Ranked
Edited
Last edited by ssqpolo; 03-01-2015 at 10:43 AM..
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03-01-2015, 10:43 AM
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CC Member
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Join Date: Jan 2015
Cobra Make, Engine: backdraft roush 427r
Posts: 17
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Not Ranked
Great replies so far. looking into exhaust options.
Basically, I'll start with exhaust, move to air cleaner (any suggestions?),and finish off with the carb if needed. Hopefully I'll get her up to full potential. I'll document along the way
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03-01-2015, 10:55 AM
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CC Member
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Join Date: Jan 2001
Location: Cape Coral,
FL
Cobra Make, Engine: 2009 Solbra
Posts: 3,861
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Not Ranked
__________________
Dan Wulff
I carry a gun because a cop is too heavy.
(No doubt, most will blame it on the donuts.)
You're just jealous because the voices only talk to me
Earth is the insane asylum for the universe.
The gene pool could use a little chlorine.
The original point and click interface was a Smith & Wesson.
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03-01-2015, 11:42 AM
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CC Member
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Join Date: Mar 2009
Cobra Make, Engine: FFR
Posts: 388
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Not Ranked
If it was breaking up you likely have something else going on.
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03-01-2015, 12:54 PM
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CC Member
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Join Date: Jan 2015
Cobra Make, Engine: backdraft roush 427r
Posts: 17
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Not Ranked
That was a small concern which I have addressed. Like I said earlier, it was running very Rich in some parts, and very lean in others, so I have been adjusting. Since it was on the dyno, I just wanted to get an idea of real whp... And frankly I was disappointed. So now, I am seeing what I can do to make more power
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03-01-2015, 03:13 PM
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CC Member
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Join Date: Feb 2006
Location: Thousand Oaks,
CA
Cobra Make, Engine: Classic Roadster
Posts: 1,367
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Not Ranked
ssqpolo I would suggest since you are in Fl that you select a carb body without the choke horn. I found with my car the air cleaner was practically resting on top of the choke horn causing an air flow restriction. Also as others have said certain muffflers can be restrictive, I picked up 80 hp by switching mine out to Classic Chambered 2 1/2" bore and also a better intake manifold.
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03-01-2015, 04:18 PM
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CC Member
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Join Date: Aug 2014
Location: Syracuse,
Ny
Cobra Make, Engine: Superformance #2660, FE-406
Posts: 372
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Not Ranked
Quote:
Originally Posted by blykins
I suppose I'm a little biased as we custom assemble our own Quick Fuel carbs. Never tried a Pro Systems, but have heard good things about them. I have sent Quick Fuel carbs all over the world (literally) and have some good reviews from my customers. The carbs that come with the Roush engines are pretty sub-par...
As far as the dyno, a 25% loss through the driveline and exhaust isn't abnormal with the Mustang dynos.
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Could you share some thoughts as to the gains seen with the suggested carbs, realizing there are likely lots of apples to oranges type issues. Still it made me curious.
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The older I get, the faster I was.
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03-01-2015, 04:26 PM
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CC Member
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Join Date: Aug 2014
Location: Syracuse,
Ny
Cobra Make, Engine: Superformance #2660, FE-406
Posts: 372
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Not Ranked
Quote:
Originally Posted by blykins
I suppose I'm a little biased as we custom assemble our own Quick Fuel carbs. Never tried a Pro Systems, but have heard good things about them. I have sent Quick Fuel carbs all over the world (literally) and have some good reviews from my customers. The carbs that come with the Roush engines are pretty sub-par...
As far as the dyno, a 25% loss through the driveline and exhaust isn't abnormal with the Mustang dynos.
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Could you share some thoughts as to the gains seen with the suggested carbs, realizing thete are likely lots of apples to oranges type issues. Still it made me curious.
__________________
The older I get, the faster I was.
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03-01-2015, 04:48 PM
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CC Member
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Join Date: Dec 2001
Location: Louisville,
KY
Cobra Make, Engine: I'm Cobra-less!
Posts: 9,417
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Not Ranked
I really don't know why the Street Avengers are turds...possibly because they are just smaller, vacuum secondary carbs, with minor adjustability.
The Q-series Quick Fuel carbs are mechanical secondary carbs, with no chokes or choke horns, and are pretty much infinitely adjustable.
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03-01-2015, 05:04 PM
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Senior Club Cobra Member
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Join Date: Jan 1999
Location: MARKSVILLE,LA.,,
Posts: 3,235
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Not Ranked
Quote:
Originally Posted by blykins
I really don't know why the Street Avengers are turds...possibly because they are just smaller, vacuum secondary carbs, with minor adjustability.
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hammer hitting the nail squarely on the head...........
David
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DAVID GAGNARD
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03-01-2015, 05:06 PM
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CC Member/Contributor
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Join Date: Mar 2012
Posts: 445
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Not Ranked
Check to make sure the throttle is opening all the way. Some backdrafts had a problem with the gas pedal bracket bending and there was no amount of adjustment that would make the carb go WOT. My car dynoed 383rwhp before fixing the pedal assembly so that it wouldn't bend when you push the pedal, and it now makes 482rwhp. It was running rich and the a/f was very bumpy.
Also, was this with or without an air filter, and which air filter? My little K&N ate up something like 30rwhp (EDIT: It was 21rwhp).
Last edited by itstock; 03-01-2015 at 05:19 PM..
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03-01-2015, 05:10 PM
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Senior Club Cobra Member
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Join Date: Jan 1999
Location: MARKSVILLE,LA.,,
Posts: 3,235
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Not Ranked
Quote:
Originally Posted by itstock
Check to make sure the throttle is opening all the way. Some backdrafts had a problem with the gas pedal bracket bending and there was no amount of adjustment that would make the carb go WOT. My car dynoed 375rwhp before fixing the pedal assembly so that it wouldn't bend when you push the pedal, and it now makes 482rwhp. It was running rich and the a/f was very bumpy.
Also, was this with or without an air filter, and which air filter? My little K&N ate up something like 30rwhp.
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SSQPOLO: real world results from too small an air filter........check out this recent thread on air filters:
Air Filter Calculator
David
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DAVID GAGNARD
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03-01-2015, 05:22 PM
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CC Member/Contributor
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Join Date: Mar 2012
Posts: 445
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Not Ranked
Quote:
Originally Posted by DAVID GAGNARD
SSQPOLO: real world results from too small an air filter........check out this recent thread on air filters:
Air Filter Calculator
David |
I added my real world experience to that thread. |
03-01-2015, 05:30 PM
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CC Member
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Join Date: Jan 2015
Cobra Make, Engine: backdraft roush 427r
Posts: 17
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Not Ranked
Wow. Very interesting information. Had no idea such massive gains could be made from intake and exhaust.
I will probably leave the carb for last, exhaust and intake first.
I have been searching, but which air filters do you recommend? I have the stock one that comes with the Roush 427r crate motor.
Sorry for all the questions, this is my first old style carb motor
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03-01-2015, 05:44 PM
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Senior Club Cobra Member
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Join Date: Jan 1999
Location: MARKSVILLE,LA.,,
Posts: 3,235
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Not Ranked
Quote:
Originally Posted by ssqpolo
Wow. Very interesting information. Had no idea such massive gains could be made from intake and exhaust.
I will probably leave the carb for last, exhaust and intake first.
I have been searching, but which air filters do you recommend? I have the stock one that comes with the Roush 427r crate motor.
Sorry for all the questions, this is my first old style carb motor
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What is the diameter of your present air filter and how tall is it????
use the largest diameter and tallest air filter you can fit under the hood and flow thru top will certainly help small air filters......
I'm using a 14 inch diameter x 3 inch tall air filter with a 1.5 inch drop base,but it is in a 65 Mustang and not a Cobra..... most Cobra's don't have the room/hood clearance for an air filter that size..
David
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DAVID GAGNARD
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03-01-2015, 06:33 PM
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CC Member
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Join Date: Jan 2015
Cobra Make, Engine: backdraft roush 427r
Posts: 17
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Not Ranked
I have the 14" oval. I'll have to check exact specs. Per backdraft website it's a 14" with k&n filter
Last edited by ssqpolo; 03-01-2015 at 06:36 PM..
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03-01-2015, 06:41 PM
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CC Member/Contributor
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Join Date: Mar 2012
Posts: 445
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Not Ranked
You should be fine with that filter.
I would definitely make sure your carb is going wot. It's the easiest thing to check and is a proven problem on the backdrafts.
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