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How tough are the good old 4.0L's 


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 Post subject: Re: How tough are the good old 4.0L's
Posted: Sat Dec 26, 2009 9:42 am 

Posts: 14513

Joined: 7th Nov 2004

Ride: ford falcon au3 xr8

Location: a shit suburb in sydney
NSW, Australia

Grimketel wrote:

i think the limiting factor here is the size of the charger not the engine.

Obviously the nature of the engine with regards to squareness plays a part, as well as rod to stroke ratio, but with the right top end they can be revved safely past the stock settings. it is only heresay but I have heard tell that these motors, in their design phase, where tested to 7k rpm worth of stress. The setting to just under 6k is both a saftey margin and economical factor.

ford are reknowned for detuning their motors someting fierce to accomidate relliability among the lowest common denominator.

in my case the charger is more than big enough. if i rev it past 5800 it will keep reving and keep making more boost at 6200rpm the charger makes over 13psi @ manifold so no sign of running out of puff..(charger is still supplying more air than the engine can take in)
it has been reved to 6800 before but i dont want to kill it.and @6800 the blower would be putting close to 15psi and would close to its max rated internal rpm.
i think the limiting factor (stock) would be valve springs and cam...
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