4 to 1 is best for all round performance.As you increase the size/dia of the primary pipe you move the max torque further up the rpm range,it does not increase it just moves it to higher rpm.Example a 16V 2.0 dohc 'motor' in comp trim may make the 7000-9200 rpm range with primarys of say 2"OD and 28-30" long,for road use that same engine will only need 1 3/4" OD @ 38" long.Always rembember that with headers,whats gained at the top is lost at the bottom and vice-versa......
V6 MTX
'Don't p**s up my back then tell me it's raining!!!"
'Its only nuts & bolts!'
'If I build it,fix it,upgrade it or modify it...MAYBE they will come....!
Haines Motor Sports Inc,
Dealer for 'Quaife America' & 'Autotech Sport Tuning'
SOLE USA Dealer for the American Axle 'AUSSIE BAR'...
Get a Turbo for you Zetec from HMS Inc...by 'The Demon' ...www.DemonDynamics.co.uk
..don't talk about it DO IT !!!
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