4.5 Exhaust Manifolds on a 4.2

[DCBT]

Hi folks,
I read somewhere that 4.5 exhaust manifolds are ported better than the 4.2 ones and are a good replacement for a cracked 4.2, does anybody have experience of this?
Thanks for your help

[scotty_d]

I am pulling my engine this week and going for set of Tims stainless set at act. 4.5 ported.

[ukkid35]

4.5 manifolds are a much closer fit to the gearbox, making it much more difficult to do clutch jobs. I drop the manifolds rather than attempt clutch work with them in place. This adds significantly to the time taken (remove airboxes, drain coolant, remove water rails, drop exhaust manifolds).