On a side note, why would you use a 30# bypass when you want 50# of pressure? Does that mean anything over 30# is being bled off? It seems like you'd want a 50# bypass spring.

I'm just trying to understand the system.

Bypass works on pressure differential across the filter element, not total system pressure.

So if it detects <30# of resistance it opens up? If that's the case then it's all making more sense now.

Yep, basically. Also, it is relatively rare to have the additional bypass installed in the center of the filter pad. That one is used if the auxiliary oil passages for an external cooler are utilized. This is typically only seen on heavy truck applications, like a box truck or something similar. You want to leave that one out, and then either install the 30-lb bypass in the outside opening of the filter pad, or use a plug to cap it off. If you plug it, make sure you are running a high quality filter with plenty of filtering capacity.

Got it.

So that's why OEM lines were adequate for the stock pump/horsepower, but a hi volume oil pump pushing against the OEM lines will trip the bypass valve or worse, activate the dump on the pump itself. Even switching out the OEM flared lines with barbed fittings is better than nothing?

I'm gathering parts to swap out the OEM 1/2" lines from the 454mag MPI on my 502/500hp that it replaced and was wondering if anybody knows the size of the fittings on the stock oil cooler? Looking at it I'm guessing 1/2" flare?

Also what size Allen key to pull the nipple out and remove the bypass valve under that? I already have the 30# valve in the side port.

Ideally I'll replace the whole system when I pull the motor out this winter, but it's not so feasible to do in the tight bilge as it sits and would at least like to switch out the lines for now.

So far I'm going with the Hardin block adapter and -12 lines.

I believe the stock GM one is around 11#'s or so.

The GMPP one is 30#'s.

If the differential is over 11#'s on the stock one, the bypass opens and bypasses the oil.

If the differential is over 30#'s on the GMPP one, the bypass opens and bypasses the oil.

Many don't use the 30# one, and just plug it...thus no chance of the bypass opening up.

Again, we are talking filter pad oil bypass , not the oil pump psi regulator typically called a oil pump bypass.