"Hey grumpy, now that I,ve built a really nice high performance, 350-377-383-406 sbc, what about header size, or brand of header
1 1/2, 1 5/8 or 1 3/4 , 1 7/8" etc tube headers do I need for my new engine combo?
I always get a grin when this questions asked, simply because the answer depends a great deal on the engines displacement, compression, cam timing, the basic rpm range the engine will operate in,the drive train gear ratios, and several other factors that are often ignored, like what intake design, cylinder heads are used , is the engine supercharged?, will you use nitrous?
because about 90% of the headers I see commercially offered are designed with easy installation, low production cost and ease of manufacture as the PRIMARY parameters in the design., yes there is easily available math that allows you to calculate the correct diameter and length of both the primary header tubes, their length and the collector diam. and length and the ideal exhaust pipe length and diam. but about 90% of the people asking the question, ask three more questions
(1)whats the least expensive headers that fits correctly?
(2) can I find cheaper headers?
(3)will these work with my stock exhaust system
basically making the answer to the first question all but meaningless
theres a significant variation in spark plug location between cylinder head designs, theres both strait and angle plug heads and even the angle plug heads vary a good deal between designs, and many headers won,t work with a few cylinder heads in some applications so its almost mandatory that you call and talk too the tech support guys from both the cylinder head and headers manufacturers, to ask if any specific combo has a history of clearance issues BEFORE purchasing your headers or cylinder heads or both.
and yes there are REALLY POORLY THOUGHT THRU HEADER DESIGNS being sold, and some amazingly good ones so shop carefully and ask lots of detailed questions, if you can go to car shows and join a local corvette club and look over the headers installed on other cars to get a good idea how they fit or cause issues with burnt ignition wire etc.
adding an anti-reversion baffle to a 18"-24" longer collector on open headers with the internal pipe about 1/2 the collector length tends to help scavenging on some engines, no header will function to full efficiency with any significant back pressure so take the effort to accurately measure any restriction to exhaust flow AT your upper rpm range of your engines power band and be darn sure its not choking your power curve.
keep in mind installing an (X) almost increases the effective cross sectional area, of the dual exhaust ,or collector cross sectional area to double what it had been behind a single header collector, by doubling the area that the exhaust flow sees, dropping the restriction to flow almost in half
http://www.wallaceracing.com/intake-runner-length.php
http://www.bgsoflex.com/intakeln.html
http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm
http://www.velocity-of-sound.com/velocity_of_sound/velocity_stacks.htm
http://www.swartzracingmanifolds.com/tech/index.htm
viewtopic.php?f=70&t=840&p=1273#p1273
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1 1/2, 1 5/8 or 1 3/4 , 1 7/8" etc tube headers do I need for my new engine combo?
I always get a grin when this questions asked, simply because the answer depends a great deal on the engines displacement, compression, cam timing, the basic rpm range the engine will operate in,the drive train gear ratios, and several other factors that are often ignored, like what intake design, cylinder heads are used , is the engine supercharged?, will you use nitrous?
because about 90% of the headers I see commercially offered are designed with easy installation, low production cost and ease of manufacture as the PRIMARY parameters in the design., yes there is easily available math that allows you to calculate the correct diameter and length of both the primary header tubes, their length and the collector diam. and length and the ideal exhaust pipe length and diam. but about 90% of the people asking the question, ask three more questions
(1)whats the least expensive headers that fits correctly?
(2) can I find cheaper headers?
(3)will these work with my stock exhaust system
basically making the answer to the first question all but meaningless
theres a significant variation in spark plug location between cylinder head designs, theres both strait and angle plug heads and even the angle plug heads vary a good deal between designs, and many headers won,t work with a few cylinder heads in some applications so its almost mandatory that you call and talk too the tech support guys from both the cylinder head and headers manufacturers, to ask if any specific combo has a history of clearance issues BEFORE purchasing your headers or cylinder heads or both.
and yes there are REALLY POORLY THOUGHT THRU HEADER DESIGNS being sold, and some amazingly good ones so shop carefully and ask lots of detailed questions, if you can go to car shows and join a local corvette club and look over the headers installed on other cars to get a good idea how they fit or cause issues with burnt ignition wire etc.
adding an anti-reversion baffle to a 18"-24" longer collector on open headers with the internal pipe about 1/2 the collector length tends to help scavenging on some engines, no header will function to full efficiency with any significant back pressure so take the effort to accurately measure any restriction to exhaust flow AT your upper rpm range of your engines power band and be darn sure its not choking your power curve.
keep in mind installing an (X) almost increases the effective cross sectional area, of the dual exhaust ,or collector cross sectional area to double what it had been behind a single header collector, by doubling the area that the exhaust flow sees, dropping the restriction to flow almost in half
http://www.wallaceracing.com/intake-runner-length.php
http://www.bgsoflex.com/intakeln.html
http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm
http://www.velocity-of-sound.com/velocity_of_sound/velocity_stacks.htm
http://www.swartzracingmanifolds.com/tech/index.htm
viewtopic.php?f=70&t=840&p=1273#p1273
RELATED INFO YOU NEED TO UNDERSTAND
viewtopic.php?f=56&t=961
viewtopic.php?f=56&t=185
viewtopic.php?f=56&t=495
viewtopic.php?f=56&t=1503
viewtopic.php?f=56&t=1303
viewtopic.php?f=99&t=6461&p=20459&hilit=volumetric#p20459
viewtopic.php?f=52&t=1070
viewtopic.php?f=52&t=5078
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