Junkman2008 said:Hey Grumpy, you always hear that headers give you more horsepower. How does that work and what formula can you use to determine the horsepower gain that a given set of headers may bring?
the more back pressure the exhaust system beyond the header collectors has the less effective the headers will be, but if you have a low restriction exhaust and a ram tuned intake with a matched cam timing, a tuned header can in some cases produce gains in excess of 60 hp.
as a general rule Id say your safe expecting a 25-40 hp increase in peak hp from good long tube tuned headers over stock cast iron exhaust manifolds that come on most passenger cars, but with properly matched components on a high compression engine more can be gained.
READ THESE
http://victorylibrary.com/mopar/header-tech-c.htm
http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/
USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.circletrack.com/enginetech/1 ... ch_engine/
http://www.pontiacracing.net/js_header_length1.htm
http://www.wallaceracing.com/header_length.php
http://www.wallaceracing.com/Calculators.htm
https://robrobinette.com/et.htm
https://www.gregraven.org/hotwater/calculators/qm-from-wt-hp.php
http://www.bgsoflex.com/auto.html
http://www.mk5cortinaestate.co.uk/calculator5.php
http://www.can-of-whoopass.com/index.php?pageID=car_stuff&calculator=primaries
http://forum.grumpysperformance.com/viewtopic.php?f=56&t=495&p=613#p613
http://forum.grumpysperformance.com/viewtopic.php?f=56&t=1303
viewtopic.php?f=56&t=572&p=35352&hilit=rams+horn#p35352
http://forum.grumpysperformance.com/viewtopic.php?f=56&t=185
http://www.chevydiy.com/chevy-small-block-engine-guide-exhaust-systems/
I find this graph very useful, it shows stock corvette exhaust manifolds vs headers on the same 496 BBC engine dyno test
Last edited by a moderator: