A series under crown jets
Turbo Mini Forums

I wanted to share my experience getting under crown jets machined and installed on an A series engine. Seems to be a few people asking where to get it done and without the kit/knowledge to do it at home (the guides don't exist, or photos links are dead).

I reached out to Fiennes Performance (located between Swindon and Oxford) to see if they could give it a go, luckily they'd done a few before, as well as BMW 4/6 pot engines. I provided the oil jets, which were BMW Gen 1 mini items - B11.11.7.531.576 with M8x1mm threads.

Just as a warning to add to this, check clearances of the jets when installed between the jet nozzle and your piston skirt at BDC.
If the facing/plunge cut for the jet body has been cut deep this can make clearance incredibly close.

Shane

Alternate oil jet to use is BMW part no 11 11 1 739 907, these have the ball valve internally.

Shane

So do these.