BDA Oil pump hose sizing question

[nickal]

Good day all! I am in the process of trying to finish up the assembly of my project car, an RT-4 Ralt. The hose sizing seems to be all -10 hose. However, Cosworth specifies the equivalent -12 size hose on the scavenge to oil cooler, oil cooler to tank, tank to pump inlet.
I have struggled with the near impossibility of fitting the -12 hose on the scavenge side ( engine mount and bodywork clearances at the oil cooler), and the impossibility of fitting any AN 12/1/2 BA adaptor fittings to the oil pump ( clearances).
If I plumb it with -10 adaptors, hose, etc no fitting problems at all.
But I worry about potential flow restriction....
Any of you guys out there have any anecdotal info on the workability of -10 for this install???
Thanks for your consideration,

Nick L.

[nomis]

definitely -12 from pickup to pump -12 to sump -12 to oil cooler and tank you can use -10 from the pump to the filter only
email me at s2gardiner@iprimus.com.au so I can send you SJs BDD documents

[Rick Kirchner]

Have you considered hard line through all the tight spots? You can always transition to different shapes while you maintain the cross-sectional area.

[nickal]

Have you considered hard line through all the tight spots? You can always transition to different shapes while you maintain the cross-sectional area.

Good thought! I discovered that doing some machinework (boring) allowed my -12 adaptor fittings to fit the cosworth pump.
Cheers,

NL

[dereklola]

.....................and the impossibility of fitting any AN12-1/2 BA adapter fittings to the oil pump.

Are you using an extended fitting?
I used to weld individual fittings to a 7/8" Al hex (bored obviously) - overall length about 3"
But then bought some steel ones about a decade ago - 4" oal.

Ah - didn't see your 7.44pm reply - but extended fittings as above are still easier to install.

[Charles Warner]

Opening up the pass-through in the RHS motor mount helps. You should have no problems with the oil cooler fittings.

[nickal]

Opening up the pass-through in the RHS motor mount helps. You should have no problems with the oil cooler fittings.

Well, I enlarged the opening as far as I could and it was still a problem. What I have now is -10 adaptors in the oil pump that have machined internally to an ID approx .032 diameter larger than a -12 adaptor fitting. The -12 adaptors ( just the 1/2 BSP to AN 12) have a .040 +/- neckdown internally. So that would be a choke point BELOW -10 cross section! I Bored it out so that there is no flow restriction at the fitting.
I have everything finally in place using -12 everywhere but the pressure lines to/from the filter. A real PIA I must say. I WILL be preheating the oil just as a little insurance......

Thanks to you guys for your responses!
Nick L.

[Charles Warner]

I would be interested in seeing your setup. I have owned at least 7 RT-4s and have never had any real problems in this area. Most people would slightly round off the edges of the oil pump fitting and line fittings to allow for clearance. It can be a pain to tighten things up with only 1/8 turn on the fitting allowed. Could it be your pump is slightly different?