high rpm
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From: las vegas',nv
high rpm
i read somewhere onth internet :
shortie headers make power at the top of your rpm range
and
longtbe headers make power down low .
if this is true wouldnt shorties be better on an lt1 since it lackes power on the top end ?
shortie headers make power at the top of your rpm range
and
longtbe headers make power down low .
if this is true wouldnt shorties be better on an lt1 since it lackes power on the top end ?
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Joined: Jan 2002
Posts: 5,308
From: Oshawa - Home of the 5th-gen
I would've thought it would be the opposite, but hey, I've been wrong before!? 
For your LT1, if you don't plan to do any major mods beyond just the headers, you would probably benefit from ANYTHING, short, mid, or long tube. For just an average "street/strip" application, mids would probably be more than enough (considering the rest of the engine ... heads/cam ... would then be the limiting factors). Lots of guys run LT's on their LT1's though, and they will ultimately help provide the most top end gains (and leave room for a heads/cam upgrade down the road
).
For your LT1, if you don't plan to do any major mods beyond just the headers, you would probably benefit from ANYTHING, short, mid, or long tube. For just an average "street/strip" application, mids would probably be more than enough (considering the rest of the engine ... heads/cam ... would then be the limiting factors). Lots of guys run LT's on their LT1's though, and they will ultimately help provide the most top end gains (and leave room for a heads/cam upgrade down the road
).
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Joined: Nov 1998
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From: Hell was full so they sent me to NJ
In "theory", making the primaries longer moves the power band down to lower RPM. Just like the runners on the intake manifold..... long runners = low end torque, short runners favor high end HP. But I've seen dyno tests on long tube headers that produced results that are not necessarily consistant with the theory.
If going to a shorter primary moves the power band upward in the RPM range, whether its a good idea depends on how the engine is used. For a street engine, you want a good bottom end, and to build "area under the curve" starting at as low an RPM as possible.... hence LT's for the street. A race engine that never operates below 5000RPM all the way down the track may produce better results with a shorter primary.
For a "stockish" LT1, you need to attack the breathing on both ends (intake and exhaust) to make a significant increase in top end HP.... just going to a shorter primary isn't going to add HP unless the engine can get the air it needs to make HP at the higher RPM.
If going to a shorter primary moves the power band upward in the RPM range, whether its a good idea depends on how the engine is used. For a street engine, you want a good bottom end, and to build "area under the curve" starting at as low an RPM as possible.... hence LT's for the street. A race engine that never operates below 5000RPM all the way down the track may produce better results with a shorter primary.
For a "stockish" LT1, you need to attack the breathing on both ends (intake and exhaust) to make a significant increase in top end HP.... just going to a shorter primary isn't going to add HP unless the engine can get the air it needs to make HP at the higher RPM.
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From: Oshawa - Home of the 5th-gen
Is that to do with (dare I say it) "back pressure"?? A long primary will provide some back pressure and help low end?? A short(er) primary has low(er) or no back pressure, and helps more up high??
But are you saying that a traditional "long tube" vs. "short tube" is going to be better for low end vs. top end, respectively? That's the opposite that I've always read/believed 
. Heck, I've even read debates that running LT's will make for "no back pressure, therefore no bottom end" (I've never supported the back pressure argument, but have agreed with / believed that they've been more beneficial for top end gains vs. low end?? 
).
Now I'm confused!!
A long primary will provide some back pressure and help low end?? A short(er) primary has low(er) or no back pressure, and helps more up high?? But are you saying that a traditional "long tube" vs. "short tube" is going to be better for low end vs. top end, respectively?
That's the opposite that I've always read/believed . Heck, I've even read debates that running LT's will make for "no back pressure, therefore no bottom end" (I've never supported the back pressure argument, but have agreed with / believed that they've been more beneficial for top end gains vs. low end?? ).Now I'm confused!!
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Posts: 71,098
From: Hell was full so they sent me to NJ
But are you saying that a traditional "long tube" vs. "short tube" is going to be better for low end vs. top end, respectively? That's the opposite that I've always read/believed . Heck, I've even read debates that running LT's will make for "no back pressure, therefore no bottom end" (I've never supported the back pressure argument, but have agreed with / believed that they've been more beneficial for top end gains vs. low end?? ).
Now I'm confused!!
That's the opposite that I've always read/believed . Heck, I've even read debates that running LT's will make for "no back pressure, therefore no bottom end" (I've never supported the back pressure argument, but have agreed with / believed that they've been more beneficial for top end gains vs. low end?? ).Now I'm confused!!
For some very basic info on exhaust system design, look into the David Vizzard book on "How To Build Horsepower - Vol. 1". A couple of relevant quotes:
BACKPRESSURE VS. POWER
Over the years, I've heard many claims from so-called experts. One I've heard more than once asserts that a performance engine - or any convertional four-cycle engine for that matter - needs some exhaust backpressure to optimize efficiency. This pronouncement was most certainly made by someone who had never used a dyno or carefully evaluated how exhaust system flow affects performance. I have no doubt that someone, someplace, at some time produced a power curve that "absolutely proved" that an increase in backpressure resulted in an increase in power. My years of dyno experience tell me that this test must have been done under questionable conditions. I have found that reducing backpressure always improves power and fuel economy, providing of course that the air/fuel ratio and ignition timing are carefully optimized both before and after the exhuast system pressure is increased......... let me tell assure you that if you minimize exhaust backpressure and optimize the engine for those conditions, 999 times out of 1000 you'll find more horsepower at the back wheels.
Over the years, I've heard many claims from so-called experts. One I've heard more than once asserts that a performance engine - or any convertional four-cycle engine for that matter - needs some exhaust backpressure to optimize efficiency. This pronouncement was most certainly made by someone who had never used a dyno or carefully evaluated how exhaust system flow affects performance. I have no doubt that someone, someplace, at some time produced a power curve that "absolutely proved" that an increase in backpressure resulted in an increase in power. My years of dyno experience tell me that this test must have been done under questionable conditions. I have found that reducing backpressure always improves power and fuel economy, providing of course that the air/fuel ratio and ignition timing are carefully optimized both before and after the exhuast system pressure is increased......... let me tell assure you that if you minimize exhaust backpressure and optimize the engine for those conditions, 999 times out of 1000 you'll find more horsepower at the back wheels.
The length of the primary pipe will only correctly time the (resonant) pulse arrival for a narrow engine-speed range. If the primary pipe is relatively short, the resonant effect occurs in the upper speed ranges; if it is relatively long, the effect occurs in the lower speed ranges.
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Joined: Jan 2002
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From: Oshawa - Home of the 5th-gen
Holy information, Batman!! 
Fred, you rock!!!
Ok, I realize my question/comment sure sounded back-pressure oriented .
Let me say out right: I don't believe the "myth" about backpressure = "good". We dyno'd my Dad's car with and without the caps on the cut-outs ... it picked up 18 rwhp with wide-open exhaust. Also, at the track we picked up a few MPH by opening up the exhaust. SO, I realize that the free-er the exhaust flow, the better.
But back to my question: are you saying that a traditional long-tube header (ie: Pacesetter/Hooker/Kooks, whomever) is going to increase low-end torque MORE, and high-end power LESS in comparison to a "shortie" header, which will provide less low-end gains, but more high-end gains???? That's what I'm reading out of what you originally posted (albeit, you put a lot of emphasis on "theory" and "may" in there ).
My "belief" (and I think others' too) has always been that shorties or mids are a good "improvement" over stock/factory exhaust manifolds, but to get the most power (specifically, top-end) out of an engine, you need long tubes??
Fred, you rock!!! Your confused because you're hung up on the concept of "backpressure", which has nothing to do with the benefits of long vs. short primaries. You say you don't believe you "need backpressure", but then you try and comprehend the difference between long and short primaries in terms of backpressure.
.Let me say out right: I don't believe the "myth" about backpressure = "good". We dyno'd my Dad's car with and without the caps on the cut-outs ... it picked up 18 rwhp with wide-open exhaust
. Also, at the track we picked up a few MPH by opening up the exhaust. SO, I realize that the free-er the exhaust flow, the better.But back to my question: are you saying that a traditional long-tube header (ie: Pacesetter/Hooker/Kooks, whomever) is going to increase low-end torque MORE, and high-end power LESS in comparison to a "shortie" header, which will provide less low-end gains, but more high-end gains????
That's what I'm reading out of what you originally posted (albeit, you put a lot of emphasis on "theory" and "may" in there ).My "belief" (and I think others' too) has always been that shorties or mids are a good "improvement" over stock/factory exhaust manifolds, but to get the most power (specifically, top-end) out of an engine, you need long tubes??
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