5.9 Magnum exhaust/intake combo help

jos51700 said

Whatever you do, upgrade the valve springs.

The springs in it are for low-redline (my 5.2 Dakota is something like 5200 rpm iirc) and the motor had a nice fuel cutoff rev limiter before the efi was removed.

Without the efi and with better intake exhaust, it will easily outrun the oem valve springs. This is why my dart is crippled right now!

Click to expand...

The stock valve springs are fine to .450" lift, the 5.2 has .440" lift from factory. 5.9 RT has .455" . You only need springs if you go over .460"-.470" Lift.

I wound the piss out of my 5.2 in my Wrangler with .440" cam for 5-6 years without any issues, it saw 6K on numerous occasions as well as towing 2000# boat through the mountains of Oregon at 65-70.

There is no "nice fuel cutoff rev limiter" on any Magnum MPFI system. There is a rev limiter built into PCM but it cuts timing not fuel and its over 6500 rpm which can easily be raised during flashing. Same for top speed cutoff.