glenn in camino
Well-known member
Is it worthwhile to install a fitting in the center main cap and run a copper tube to the oil pump for some oil pressure. I've done this before but doubt that it helps much.
Oil pressure to center Main
- Thread starter glenn in camino
- Start date
amodel25
Senior Member
Even if the oil pump's output was 20 gallons/minute, lubrication of the main bearings is dependent on gravity flow though a finite diameter tube. By adding a line from the oil pump to the main bearing cap you are insured of getting a pressurised (albeit low pressure) film of oil on the "loaded" side of the main bearing journal. I feel that it is beneficial. I have this modification on both the front and center main of my engine.
Dave in MN
Well-known member
Glenn, If I asked my father a similar question when I was a lad, his stock answer would have been; Well, it couldn't hurt. I think that answer applies to your question if done carefully.
From my Model A engine re-building experience, the center main fails much more frequently than the front main and the type of failure I most often see is breaking up of the babbitt. So it is obvious to me that the center main is loaded more heavily. I see rear main and center main failure at about the same frequency. IMO Pushing more oil through the bearing has to help cool and cushion the babbitt better than less oil. I have to believe that pumping oil to the center main provides more oil flow through the bearing than the stock 4" of oil column from the valve chamber. So I think the piping helps if the actual installation of the fitting at the cap is completed in a manner that does not significantly weaken the bearing assembly.
When I build an engine with a target of producing 55-65HP, I always include this extra step. I have not had one come back yet with center main failure. So, I can't say it is necessary but believe "It couldn't hurt."
Good Day!
Dave in MN
www.durableperformance.net
From my Model A engine re-building experience, the center main fails much more frequently than the front main and the type of failure I most often see is breaking up of the babbitt. So it is obvious to me that the center main is loaded more heavily. I see rear main and center main failure at about the same frequency. IMO Pushing more oil through the bearing has to help cool and cushion the babbitt better than less oil. I have to believe that pumping oil to the center main provides more oil flow through the bearing than the stock 4" of oil column from the valve chamber. So I think the piping helps if the actual installation of the fitting at the cap is completed in a manner that does not significantly weaken the bearing assembly.
When I build an engine with a target of producing 55-65HP, I always include this extra step. I have not had one come back yet with center main failure. So, I can't say it is necessary but believe "It couldn't hurt."
Good Day!
Dave in MN
www.durableperformance.net
Last edited:
Jim Brierley
Well-known member
Right, it can't hurt! I believe the main advantage of the added line is that the main gets oil almost immediately instead of having to wait for oil to be pumped into the galley then gravity flow down.
Bruce
Senior Member
Piranio's (www.modelaparts.net) sells a kit that includes the brass fittings and a piece of steel tubing that is priced way less than it would cost you to drive to town and buy the pieces -- even if you don't log your time. Dennis also 'splained to me that the best place to into the passage that the oil pump feeds can vary, depending on differences in Model A blocks.