Pre-oiler question

[olddog]

Originally Posted by DAVID GAGNARD

the oil pump was a stock replacement parts store oil pump........on start up,the oil pressure gauge would sit still for at least 3 seconds, then slowly go up to 50 psi, and I mean slowly, but acceptable......

On my Melling High Performance oil pump, standard pressure/volume, on start up, the oil pressure instantly goes up to 60 psi, and I mean instantly......
David

To be scientific, I would have to consider that the sender/gauge combination in the two different vehicles could be different. Capacitors make great filters, but they add lag time. You would have to test both engines with the same mechanical gauge to be certain.

Honestly gear pumps can have poor efficiency if they have too much clearances, which causes low flow at high pressure. I cannot see a mechanical reason that could cause one to build pressure slowly.

PS
It occurred to me that if all the oil drains back to the pan on an engine, the pump is going to take time to fill the passages and it will be compressing air as it pushes it out. On the other hand, if the passages do not drain back, oil is not compressible and the pressure would be instant. Perhaps a loose pump would allow drain back where a tight pump would slow that process down. That said I could be wrong.

[DAVID GAGNARD]

Originally Posted by olddog

To be scientific, I would have to consider that the sender/gauge combination in the two different vehicles could be different. Capacitors make great filters, but they add lag time. You would have to test both engines with the same mechanical gauge to be certain.

Honestly gear pumps can have poor efficiency if they have too much clearances, which causes low flow at high pressure. I cannot see a mechanical reason that could cause one to build pressure slowly.

PS
It occurred to me that if all the oil drains back to the pan on an engine, the pump is going to take time to fill the passages and it will be compressing air as it pushes it out. On the other hand, if the passages do not drain back, oil is not compressible and the pressure would be instant. Perhaps a loose pump would allow drain back where a tight pump would slow that process down. That said I could be wrong.

I agree a pump with a lot of clearance will build pressure slower, that's why I think the precision made Melling pump was better than the generic parts store pump....I didn't use the same gauge, but do/did check the gauges for accuracy as I do all my gauges before I install them....
I think the High Performance line of pumps are made to tighter tolerances than the generic pumps, that's why they get the pressure up quicker, they are more efficient to begin with...

David