Oil filter bypass

[Yoda4561]

The filter bypass valve is inside the oil filter, not sure how you'd lock it closed without destroying the filter in the process. Also if your filter is going into bypass it's to ensure full oil flow during high RPM/plugged filter conditions, to prevent starving your engine of lubrication. Is the filter only doing this on a cold engine, or does it still do it even when it's fully warmed up?

One thing I'd try before dinkering around with the bypass valve is the amsoil EAO oil filters, they're a 100% synthetic media that from all I've read has much lower resistance to oil flow than normal cellulose oil filters, while filtering as good or better than anything short of a mobil 1 or bypass filter. They're not all that expensive given that the media also has a greater holding capacity, so you only need to change it once a year or so on a mechanically sound engine. Even if you have to change it at normal intervals it's not any more expensive than a Mobil 1 filter (even better filtration, but it's a celluose/syn blend that has just as much restriction as a normal filter). Worth a try anyways, I'll be ordering some up for a 75 TA on the next oil change to see how it goes.



edit: dug around a little, about halfway down the page seems to be a list of EAO specs, I think your engine is an EAO25, and the bypass valve pressure is listed as N, which I assume means it doesn't have one. http://www.bobistheoilguy.com/forums...&Number=355077

[vette427-sbc]

Is there another oil bypass then? The guy I spoke to showed me a piece that he had blocked off by using a tap and a pipe threaded bolt.
I tested it right after an oil and filter change and it still had the same symptoms- hot or cold

[Yoda4561]

I don't know much about the finer points of GM oiling systems, maybe there's an internal bypass in the engine, hopefully one of the chevy guys can chime in and get you fixed up.

[vette427-sbc]

Here is the bypass or "relief valve" I was talking about...




I found a very good explanation of how/why it works written by TwinTurbo:

You have to realize that it's not the system pressure of 15psi that opens it but a pressure DIFFERENTIAL of that over the filter. Basically a pressure drop due to cold/thick oil, a clogged up filter......

Everything is relative so even with a 15psi spring setting on the relieve valve, it only opens when one side has 15 psi less than the other side, whether this is 30 vs 15psi, 50 vs 35, 80 vs 65...blah blah blah...doesn't matter.

The oil filter is NOT on a side loop, it only is if you forget the hidden plug in the rear vertical passage. The oil filter adapter only bypasses to keep the filter from bursting. I have always replaced the spin on adapters with non bypassing ones and used either large case filters or a System 1 mesh filter. Never had a problem. Especially with the System 1 filter it takes a ton of pressure to burst that thing. So, if you have a pressure drop of more than 12-15psi over the filter, that's when the bypass opens.

The bypass valve in the PUMP is what bypasses the oil back to the sump to regulate max. system pressure. If that one opens the oil gets routed back into the sump via the relief port.

Going to try and block it off tomorrow and see what happens