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Beautiful, seems my message failed. Again.... Any chance you have pictures of how you modify the pumps? I can't find but one picture online, and it doesn't actually show how the mods were done. Looks fairly easy on the BBC-style pumps, just curious how you handle blocking off the passages (drill/tap for set screws?) and how you plumb the discharges.
Thanks for the update. I like the M99HVS pump especially for race engines, I modify it so that when the pump is operating at max pressure, the oil flowing into the regulator passage doscharges back into the pan instead of being churned in the pump. Its probably not necessary but for wet sump engines running 100+ lap races oil temps are a real concern, plus i've had good lucj with that setup and hesitant to change.
My *guess* is that the BBC-style pumps, with the cast in recess at the discharge, are far less affected by this offset. If a real, stock, SBC pump was tested in flow against a BBC-style pump, it would almost certainly fare far worse than what is shown in at least the car craft test.
For most probably not an issue, but to me, it is interesting, what with the standard/HV debate.
I'll also add that the images of the M55 pump show a BBC style cast recess, but shallower, and the M55A shows no recess.
Not the best photos, but I think they are clear enough. I checked out the Car Craft oil pump test http://www.hotrod.com/how-to/engine/...evy-oil-pumps/ and then checked out the Milodon pumps. What was tested in that article is not representative of what GM has been installing at least since the 1990's. The Milodon pumps all clearly show the pump discharge to cap mating area utilizing a casting similar to what the stock BBC pumps have always used...a cast in recess in the pump casting where it meets the main cap.
I calculated the "restriction to flow" caused by the stock GM SBC pump misaligment with the main cap in this setup, and the misalignment cuts off just over 20% of the area of the discharge port on the pump. Obviously the differences could be less or more with tolerances, FWIW the M99HVS has better alignment on the same motor.
I appreciate the guidance, FWIW I ended up purchasing the M99HVS pump. Melling (George Richmond) gave me the same suggestion when I had asked about their shark tooth pumps.
Just some information, if you didn't already know it. Pulled apart two GM 5.7L SBC Vortecs (gen1 blocks), one a new production (2015) long block. The 2015 one had a pump with "M155" cast into it.
I noticed there is a specific difference in the BBC and SBC pump design in the cap mating surface. I documented the differences photographically here: Oil Pump by Dorian Yeager | Photobucket
Do you have a parts recipe of what fits? Anything that works with a stock 5qt pan? I talked with Milodon, their recommendation of pump and pickup was accompanied by a large 7qt pan, which I suspect might be from a difference in how the pickup sits, but if I don't need a large pan to clear, I'd rather not run one. I'm guessing clearance to bottom of pan can be an issue depending on the pickup and the height of the BBC pump compared to SBC.
I've noticed a few manufacturers are making the 5 bolt BBC pumps specifically for the SBC (melling, milodon, etc) but I'm not sure what they are doing to a stock BBC pump, other than anecdotal comments that there is a different angle somewhere.
It's a low RPM truck engine that needs more oil at low RPM's, the BBC pump is something I'd like to try out...see if there is a difference, since I can compare to the present small block setup.
I'm not going to exceed 4500RPM's, nor a hardcore offroad rig that will see extreme angles.