vacum source question

32sbct · Post by **32sbct** » Fri May 27, 2011 8:15 am

Background, I'm still debating whether to keep the MB engine I have for my M38 or try to go with an M38 motor. Two questions.

1. Can the m38 fuel/vacuum pump be mounted on an MB engine block? I think it can but just want to check.

If the standard MB fuel pump is used, is there another source for vacuum to run the M38 wiper system?. I have the parts of the wiper system that are attached to the windshield frame still with the jeep. Not sure if they work or not but everything is there and I want to keep the original look if possible.

Thanks as always for your thoughts/suggestions.

RimfireJim · Post by **RimfireJim** » Fri May 27, 2011 9:23 am

1. Not sure, but you may run into an interference problem with the front mounting plate on the engine. There was some discussion about an M38 pump and a civvy plate in ocwd's progress thread here: http://www.willysmjeeps.com/v2/modules. ... &start=120

2. You can port it to the intake manifold, but the vacuum level (and wiper performance) will fluctuate with engine load/throttle opening. It will be as good (or bad) as most vehicles of the era that had vacuum wipers. Without the dual fuel/vacuum pump, there is no source of constant vacuum on the engine.

Post by **wesk** » Fri May 27, 2011 9:50 pm

If your MB engine is using a M38 front mount plate then the M38 dual vac / fuel pump will work. If you have the MB front plate (both ears facing aft) it won't.

The manifold vac system alone is inadequate to operate a pair of vac wipers. It must be boosted by a dual vac/ fuel pumps or have a reservoir system added.