If you want to take more load of then remove the spark-plugs. You will have less pressure on your bearings and it will be cranking faster at the same time.
I am not familiar with the engine but if it has a mechanical oil pressure gauge you should see the pressure build up pretty good with the obtained starter motor cranking speed and the plugs out.

Good luck j

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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
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85 lebaron convertible, to be electric
85 lada niva 4x4 with 1.9 peugeot diesel,
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77 Jaguar XJS, LPG
73 corvette 350 auto
88 MB Gelande 240 GD military
98 Ford E350 mini bus to be new 4x4 camper