Dyno testing Corvette Manfolds against headers
Melting Slicks
Joined: Apr 2009
Posts: 2,632
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From: Great Plains Iowa
Chinese Headers
With the Chinese now making long tube headers we can waste less money than we did before. Now if we can just get the Chinese to manufacture 750 cfm mechanical secondary carburetors for our L-48's with their TH350's and 3.08 rear ends.
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You already have mechanical secondaries with the Q-jet.
And yes the Chinese already make 750 DP's....actually not real bad ones....
Once we "fix" an L-48 we'll have something that will spank an L-82 and an LT-1!!
Or if you just want an L48....heck I wouldn't advance the timing or change the mufflers, or tweek that Q-jet secondary air valve opening rate or anything so it wouldn't scare me when I went wild and crazy and shifted at 3600 RPM!
This is just too fun...like a train wreck...I have to keep coming back to see what happened!
JIM
And yes the Chinese already make 750 DP's....actually not real bad ones....
Once we "fix" an L-48 we'll have something that will spank an L-82 and an LT-1!!
Or if you just want an L48....heck I wouldn't advance the timing or change the mufflers, or tweek that Q-jet secondary air valve opening rate or anything so it wouldn't scare me when I went wild and crazy and shifted at 3600 RPM!
This is just too fun...like a train wreck...I have to keep coming back to see what happened!
JIM
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Long Tube Headers And Gullible People
Long tube headers produce the least bang for the buck but yet they're the first uh "performance" modification most gullible people make. Gives their engine that "racy" look.
Drifting
Joined: Jul 2009
Posts: 1,534
Likes: 14
From: Dallas-Fort Worth TX
I gotta say I love my long tube headers. Would not have it any other way. Then again, not sure if my Hedmans' 2" primaries headers are considered long tube as they are not as long as the hookers, but they are obviously not exhaust manifolds either. The heat reduction/escape and sound are great. My trans and what I consider high gears (3:54) should be lower in my opinion in order to get along with the OD trans. I have to get her above 3000 rpm before it really starts to roar... Lots of fun though when it happens.
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
You already have mechanical secondaries with the Q-jet.
And yes the Chinese already make 750 DP's....actually not real bad ones....
Once we "fix" an L-48 we'll have something that will spank an L-82 and an LT-1!!
Or if you just want an L48....heck I wouldn't advance the timing or change the mufflers, or tweek that Q-jet secondary air valve opening rate or anything so it wouldn't scare me when I went wild and crazy and shifted at 3600 RPM!
This is just too fun...like a train wreck...I have to keep coming back to see what happened!
JIM
And yes the Chinese already make 750 DP's....actually not real bad ones....
Once we "fix" an L-48 we'll have something that will spank an L-82 and an LT-1!!
Or if you just want an L48....heck I wouldn't advance the timing or change the mufflers, or tweek that Q-jet secondary air valve opening rate or anything so it wouldn't scare me when I went wild and crazy and shifted at 3600 RPM!
This is just too fun...like a train wreck...I have to keep coming back to see what happened!
JIM
Back-to-back testing of my L-48, long tube headers took 0-60 time from 7.1 (admittedly, faster than a stock L-48) to 6.5 sec (faster than any mag-test I've seen for a stock L-82).
I can't remember my shift points (that was over a decade ago that it was last in that configuration), but it was definitely under 5000 RPM.
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Thread Starter
Race Director
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From: Corsicana, Tx
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I was told one time by a guy I highly respect in the performance world that "anything under 4000 RPM ought to be pulling into a parking place"!!
It's hard these days to not buy Chinese or offshore. Even most of the "good" stuff comes from somewhere else originally. Sort of like buying a car with a foreign badge....yep I know they build them here..and I know a lot of American makes are made out of the country or at least source a lot that way...but at least I know where the final $$ went. My driveway will remain full on American branded vehicles.
JIM
Last edited by 427Hotrod; Jan 14, 2016 at 02:44 PM.
Thread Starter
Race Director
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From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
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2017 C2 of Year Finalist
Back-to-back testing of my L-48, long tube headers took 0-60 time from 7.1 (admittedly, faster than a stock L-48) to 6.5 sec (faster than any mag-test I've seen for a stock L-82).
I can't remember my shift points (that was over a decade ago that it was last in that configuration), but it was definitely under 5000 RPM.
JIM
Had a 1976 L-82, 4-sp
Joined: Mar 2011
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Thread Starter
Race Director
Joined: Jan 2000
Posts: 13,018
Likes: 2,262
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
Mine has A/C, PW etc etc. It was my daily commuter for years. Ford so way overbuilt those things. Forged pistons, double roller timing chain, roller cam, 8.8" posi, good clutch and trans etc etc. The Camaro's of the day weren't even close in strength.
With over 200K miles on it, it's never been apart other than when I ported the heads at 10K miles. It sat for literally 10 years and a few years ago I brought it back to life by swapping the crud filled gas tank and fuel pump, replaced the dry rotted tires and put a battery on it. Sucker literally turned about twice and fired up without a lifter tick. Drove it 1200 miles from TX to Utah in dead middle of winter snow/ice and the crazy thing never missed a beat and got up to 24 MPG! I even did a magazine article on the excursion!
Man...can we take a topic off subject?? It's my thread...so I'm Ok with it! Have at it!
JIM
Last edited by 427Hotrod; Jan 14, 2016 at 03:09 PM.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
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From: Great Plains Iowa
Loss Of 50 Horsepower Thru Mufflers
When talking about the new L-88 Zora Duntov said there is a loss of at least 50 horsepower thru the mufflers.
If long tube headers are worth 40 ft/lbs of torque and a 20% increase in fuel mileage why hasn't a single production car ever been equipped with them? Headers WILL produce more torque but only if there's nothing behind them and that's why the big three never installed them.
If long tube headers are worth 40 ft/lbs of torque and a 20% increase in fuel mileage why hasn't a single production car ever been equipped with them? Headers WILL produce more torque but only if there's nothing behind them and that's why the big three never installed them.
Dr. Detroit
Joined: Mar 2012
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From: New Braunfels Texas
Race Director
Joined: Jan 2000
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From: San Jose CA
When talking about the new L-88 Zora Duntov said there is a loss of at least 50 horsepower thru the mufflers.
If long tube headers are worth 40 ft/lbs of torque and a 20% increase in fuel mileage why hasn't a single production car ever been equipped with them? Headers WILL produce more torque but only if there's nothing behind them and that's why the big three never installed them.
If long tube headers are worth 40 ft/lbs of torque and a 20% increase in fuel mileage why hasn't a single production car ever been equipped with them? Headers WILL produce more torque but only if there's nothing behind them and that's why the big three never installed them.
20% increase in fuel mileage, not likely. I'd guess 20 to 30 lb-ft on an L-48. More engine, more benefits.
Drifting
Joined: Jan 2012
Posts: 1,908
Likes: 129
From: Fredericksburg Virginia
That's exactly why I put Hooker sidepipes and STS baffles on my 1970. The gas mileage.
I think in the most general sense, folks that go through the trouble of installing headers have already, or will shortly, swap out the factory muffler with something less restrictive.
MY COMMENTARY:
You seem to be starting the conversation with the notion that all automobile manufacturers put the absolute best parts they can put on their cars. And that the engineer's decisions associated with a vehicle's design attributes are their absolute best effort.
Unfortunately, there are bean counters involved that pull off "the best parts" and limit the size of the sandbox the engineers can play in.
Not to mention the fact that they had to produce the Corvette to appeal to a 45 year old woman just as much as a 18 year old man. That's why it wasn't a header-wearing straight-pipe demon sitting on the showroom floor.
Rams horn exhaust manifolds, pancake-flat steel intake manifolds, and nice, quiet high backpressure mufflers do not represent the best solution available at the time. They represent the consequence of reality.
Replacing the rams horn manifolds with smoothly bent headers is not a waste of money. It is a proven way to increase the efficiency of the air pump we call an engine.
You're welcome for the snack.
I think in the most general sense, folks that go through the trouble of installing headers have already, or will shortly, swap out the factory muffler with something less restrictive.
MY COMMENTARY:
You seem to be starting the conversation with the notion that all automobile manufacturers put the absolute best parts they can put on their cars. And that the engineer's decisions associated with a vehicle's design attributes are their absolute best effort.
Unfortunately, there are bean counters involved that pull off "the best parts" and limit the size of the sandbox the engineers can play in.
Not to mention the fact that they had to produce the Corvette to appeal to a 45 year old woman just as much as a 18 year old man. That's why it wasn't a header-wearing straight-pipe demon sitting on the showroom floor.
Rams horn exhaust manifolds, pancake-flat steel intake manifolds, and nice, quiet high backpressure mufflers do not represent the best solution available at the time. They represent the consequence of reality.
Replacing the rams horn manifolds with smoothly bent headers is not a waste of money. It is a proven way to increase the efficiency of the air pump we call an engine.
You're welcome for the snack.
Last edited by keithinspace; Jan 14, 2016 at 03:28 PM.
Race Director
Joined: Dec 1999
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From: Sierra Foothills CA
Yeah I know....I'm a "wild and crazy guy" and just throw caution to the wind sometimes!
I was told one time by a guy I highly respect in the performance world that "anything under 4000 RPM ought to be pulling into a parking place"!!
It's hard these days to not buy Chinese or offshore. Even most of the "good" stuff comes from somewhere else originally. Sort of like buying a car with a foreign badge....yep I know they build them here..and I know a lot of American makes are made out of the country or at least source a lot that way...but at least I know where the final $$ went. My driveway will remain full on American branded vehicles.
JIM
I was told one time by a guy I highly respect in the performance world that "anything under 4000 RPM ought to be pulling into a parking place"!!
It's hard these days to not buy Chinese or offshore. Even most of the "good" stuff comes from somewhere else originally. Sort of like buying a car with a foreign badge....yep I know they build them here..and I know a lot of American makes are made out of the country or at least source a lot that way...but at least I know where the final $$ went. My driveway will remain full on American branded vehicles.
JIM
Melting Slicks
Joined: Mar 2008
Posts: 2,989
Likes: 198
From: Meriden CT
I still want to see chassis dyno tests comparing cast iron manifolds versus long tube headers and using stock mufflers. I'd be willing to bet the gain would be too small to offset the expense and increased interior heat. For drag or track use I can certainly see an advantage to using long tube headers but not for steady point A to point B street use where revs rarely exceed 3500 rpm.
http://www.google.com/url?sa=t&rct=j...7QOv5rZxDzXv2A
Now please shut up.
Last edited by SH-60B; Jan 14, 2016 at 04:07 PM.