For the HIH I use 3/8" SS tube and 5/16" SS for the return inside 5/8 coolant hose Mc Master . For the fuel line Tygothane designed for Bio Diesel (McMaster)
2 Pumps 5-9 psi plunger pumps. see fattywagon
Bypass old pump
2 check valves before IP.
One 3 way valve after IP.

Modified the pressure valve at the IP housing from 15-18psi to 5 psi. (different spring)

Inside WVO tank is a container ( thickwall aluminum budweiser BOTTLE with holes in the bottom. The warm return fuel mixes with the WVO.
but reduces heta buildup in the tank ( see I believe fattywagon website)

I use GMC 3500 diesel filter in the back next to the WVO tank. It has a couple of turns 5/8 soft coolant line around ( get more surface contact) .
I experimented with the WVo filter in the front or back and I measured that the WVO at the IP gets hoy much quicker with the filter in the trunk.

I use electronic induction heating around the injection lines and that is the ticket. a constant 200-220 F at the end of the injector line.

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85 MB 300TD with om616 4 spd
83 MB 300TD
83 MB 240D scrapped
82 MB 240D scrapped
97 Ford E350 diesel 4x4, WVO
94 Ford E350 4x4 diesel blown head..parts car
85 cherokee diesel 2.1, 300.000, WVO
85 cherokee diesel 2.1
85 lebaron convertible, to be electric
85 lada niva 4x4 with 1.9 peugeot diesel,
72 citroen DS 5spd, LPG
77 Jaguar XJS, LPG
73 corvette 350 auto
88 MB Gelande 240 GD military
98 Ford E350 mini bus to be new 4x4 camper