Fevre

What pressure does the bypass open at in the adaptor? I believe it is called a high pressure bypass, I know it routes unfiltered oil into the eng which is the greatest thing. I know you can alter it to not allow it to happen but I decided to get a premade adaptor without the bypass. Also is there any pressure increase when the bypass is eliminated?

Second questions gen how how much of an increase does a high volume oil pump cause on oil pressure? Mine is not up where I wanted on my current 383 I am trying to just a bit higher. I am planning a all forged 383 but want to give this a go for a summer or 2.

Thanks

442olds

It would be highly unlikely that you see an increase in pressure by not having the bypass. I think it kicks in when the pressure differential across the inlet and outlet of the filter is about 10 psi. Ie pressure in is greater than pressure out. So in theroy it should never open unless the filter is clogged. But I don't think it works that well.

As for going from a stock melling replacement to a high volume melling, you'll see at speed pressures (non idle) hit as high at 90 on a cold start and it should run consistantly at about 60 to 70 (cruise to WOT). Idle will drop down to 15 to 25 depending on oil viscosity and the temp of the oil. Hot day, lower pressure at idle, hit the gas and up it goes right back to where you want it in the 60 to 70 range. A stock pump doesn't usually get above 50 to 55.

And remember anything more than 10 psi per 1000 rev's is stealing power. :D

Deburr the pump casting (lots of casting flash and mold line seppage in the bottom plate passage), polish the main cap area and blend the area where the oil enters the rear main and up into the block. It'll help decrease any pressure drops involved.

Turbo-Jet

:iagree:
And also check the gear clearance in the housing. Endplay should be .002-.003. My worn out stock pump was .0055. The replacement pump was .004 out of the box, so I lapped it down to .0025. Big improvement in pump efficiency and this type of rework would be done during any 'blueprinting' job.

71coupe

Fevre - If you switch to a high volume, your idle pressure will increase around 15 psi. I also had the same concerns when my idle oil pressure hovered around 18 psi hot. After I installed the hi vol, idle pressure never drops below 34 psi. A high pressure pump or high press spring will do nothing for idle pressure.
:cheers:

Fevre

I am at 15 at 800 rpm idle, 10w40 and 30/40 degree air temps so it sounds like a high vol pump might be just what I am looking for. :thumbs:

71coupe

Man you are up early (or late) Do you work the grave shift? One of these days I'll get a real job with normal hours. :sad:

gerry72

If that is your pressure at idle with that weight oil at that temperature, a HV, HP, or HV/HP pump will only superficially mask the problem.

If your bearing clearances are good, you should be able to run around 30psi or so at a hot idle.

While the main and rod bearings usually get the blame, low pressure problems are almost always in the cam bearings.

Fevre

Yes this is a band aid approach but as stated I am just trying to get a summer or two out of it, I have a 350 short block that can go in but thought I would spend a few $ and hours rather than a few hundred $'s and a few days.

Twin_Turbo

as olds said, it opens when there's a differential pressure larger than the spring pressure in the bypass. The bypass however lets unfiltered oil into the engine, not a good thing at all. IT opens when the engine is cold and the oil has a higher viscosity. I don't even run a bypass style adapter. You can eliminate the thing and run a large filter, the large filter is a good idea since the smaller filters can be overstrained and rupture.