Hmm - I've had a few 4203 engined LR's and I can honestly say I can't remeber the servo set up - I don't think that any of them went fast enough for the brakes to be an issue.
As for vacuum pumps very few 4203s are likely to have them as most of these engines came out of stationary generators and forklifts - neither of which have much call for brake servos. You can tell if it is a stationary engine because the cranks weren't counterweighted and your head will hit the rooflining that bit harder at idle....
Seriously tho' - good thoughts about modifying a Ford Di alternator, the only alternative I can offer is to modify an inlet manifold vacuum butterfly assembly from a series III 21/4 diesel and tap the inlet behind it so that the servo charges on over run (same as in the LR engine setup). Main problem with this is that 4203s sit fairly tall and the inlet manifod points straight up which means you'll run short of space.
The other alternative is to fit 6cyl or stage 1 backplates and drums, sod the servo and build up your leg muscles!
PS my father in law worked for Perkins for 40 years - I'll ask him if he has any suggestions
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Seriously tho' - good thoughts about modifying a Ford Di alternator, the only alternative I can offer is to modify an inlet manifold vacuum butterfly assembly from a series III 21/4 diesel and tap the inlet behind it so that the servo charges on over run (same as in the LR engine setup). /quote]
The problem with this idea is that the engine will probably not be tolerant of the sudden high vacuum created in the whole inlet manifold and cylinders, and you might find it sucks a whole lot of oil down the inlet valve guides or up past the pistons.
It's worth remembering that diesels can be be designed with the knowledge that they will more or less never to go into high vacuum in the inlet side, whereas spark ignitions engines are in high vacuum except when you have your foot hard on the go pedal.
It is always quite a good idea to find and fit a vacuum tank, and fit a vacuum gauge to show that you have decent vacuum level and thus good brakes assistance.
CharlesY
Edit: What the heck is that beer can!, I hope thats not a flexible exhaust coupling, cheeky but nice.