Outer Limits 4x4 Board

Hi, i have heard of people fitting 4.5 patrol heads to tb42 blocks and i would like to know if there are any mods that need to be done and what the gains are from doing it?

thanks

There was a thread about this not long ago where the consensus was that the head will bolt right on.

Only drawback is you cant the carby setup from the 42, you must run the EFI from the 4.5 or an aftermarket EFI setup.

A TB45 is really just a TB42 that's been bored out an extra 3.5mm on each cylinder. Same stroke, basically the same everything, same two valves per cylinder, same pushrod technology.

Given that an actual TB45 is only ~30HP better than a TB42, I can't see swapping a head gaining you much at all. I mean most of the extra 30hp must come from the extra 0.3 litres of displacement, probably little or none of it comes from any differences in the head.

It's the TB48 that is really an improvement in the series, with some actual new technology like double overhead cams, 24 valves, and variable valve timing instead of the 12-valve pushrod arrangement of the 4.5 and 4.2

There does seem to be a bit of a myth out there that a TB45 head can turn a TB42 into a TB45, but the difference is in the bore, not in the head.

TB42: bore 96mm, stroke 96mm
TB45: bore 99.5mm, stroke 96mm
TB48: bore 99.5mm, stroke 102mm

So my guess is it can probably be done but that there is no benefit to justify it.

Bogged wrote:YMMV!

Also I personally havent heard any TB45 heads crack. So that might be a better option in terms of replacing the head to one .

rOd wrote:Also I personally havent heard any TB45 heads crack. So that might be a better option in terms of replacing the head to one .

I was thinking along the same path that if you had to replace your head the 4.5 might be a better choice to source from due to being younger, possibly improved.

chimpboy wrote: Given that an actual TB45 is only ~30HP better than a TB42, I can't see swapping a head gaining you much at all

his TB42 eats TB42 heads. possible better option with the 45 head