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Old 01-18-2009, 07:57 PM   #1
Senior Member
Join Date: Dec 2008
Location: San Diego
Posts: 502
Amsoil Restrictor Valve Removal

IF you have or are considering removing the restrictor valve from your older Amsoil Dual Bypass oil filter head please consider my following comments. I installed my bypass filter in 2005 after the front u-joint crushed the stock filter and housing. Like other 6.0's I have had reverse flow till now. My thanks to the sharp SMB enthusiast who discovered that just recently. FYI - I was on my 3rd filter set. After noting that my filters were barely warm after running the engine for 5 hours I decided I better investigate and not take the Sportsmobile West recommendation to swap the lines on the next filter change. (another 5K mile for me). A big part of the reverse flow thread was the restrictor valve removal. I completely removed my filter head and made some comments about that last week. I identified the restrictor valve (RV) as a pressure regulating valve (not thermostatic). It will seek a pressure balance and in the process restrict flow to the full flow filter. I left the RV out when I reassembled everything. I had my doubts so I performed 2 tests. These are very crude and I only had 2 120 degrees cheap hiking thermometers. Yesterday I taped them to the bottom of the filters and took readings every minute till they reached the max 120 degree. I put the RV back in and performed the same test today. I have the AIC so I did both tests on Charge Protect (1600 RPM). In summary what I found is that w/o the RV the full fillter has a 15 degree hotter delta and with the RV there is about a 7 degree delta initially decreasing down to a 2 degree delta as the oil reached 120 between the 2 filters. Now of course the oil gets much MUCH hotter but my interpretion of this is that as the oil heats up the RV will provide the increasing back pressure to keep flow going to the bypass filter. Possibly even increasing the back pressure (more flow to the bypass filter) as the viscousity decreases. In my (very) humble opinion you should not remove the restrictor valve. As to the comment that the new filter head does not have one if you look at the AMSOil literature I note that the Full Flow filter is now closest to the supply lines and the bypass filter is farther away. I do not know how it is constructed so I have to discount that as a reason to remove the RV. If you have the older filter head you will get more flow through the bypass filter with the RV in place. That is an irrefutable statement. I'm leaving mine in.

My next test will be swapping my lines back to reverse flow (for a few minutes) and proving that the current filters with the built in backflow preventors (orange rings seen through the outer holes) reduce the filter flow to a trickle. I can do this because I have the sampling valve and in the reverse flow configuration it is on the other side of the pressure. Flow equals heat transfer, no heat, no flow, no filtering. All SMB said in their statement was that the engine operated within its normal oil pressure parameters. I have no trouble believing that. My concern is the at least 4500 miles with no filtering what so ever.

It will be about a month before I get the results of my oil analysis. I still believe that the original filters that I got from SMB 3 years ago allowed some reverse flow. The filters I just took off which I got from direct AmSOil 1 year ago did not. Maybe the anti drain flap was a recent filter improvement.

All of these statements and conclusions are strictly mine. As I said before I just happy to be filtering now!

Pat O

2004 SMB 4x4 RB 6.0 PSD; ARP Head Studs, Gen 3 Cylinder Heads, BPD Oil Cooler connected to AMSOil Bypass, a whistling Wicked Wheel Turbo, Coolant Filter, Upgraded alternator, ScanGauge, SCT custom and SMB Fox shocks.
BFG 285/75 R16 KM3 Mud Terrains on ProComp 7069's
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Old 09-21-2015, 11:28 PM   #2
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Join Date: Sep 2015
Location: Soldotna, Alaska
Posts: 50
Re: Amsoil Restrictor Valve Removal

Hi Pat O., I realize that your post was almost seven years ago, but I'm interested in the results of your followup test and whether you believe that any significant damage was done to your engine by the SMB / Amsoil filter system being plumbed backwards by SMB West's apparently widespread installation blunder? (I'm a newby to the forum,.. Please read my post on page 14 of the "John and Dana" original "Amsoil warning" thread for more background) My 2006 6.0 L diesel was most likely exposed to 25,000 miles of this reverse-pumbed condition,.. perhaps as much as 15,000 to 19,000 miles of that may have been on the same oil (no records of what oil changes, if any, occurred before I bought it), and I have put 5000 miles on a new change of Amsoil DME oil and a new set Amsoil filters but with the hoses still backwards. I am totally disgusted with the lack of integrity of Sportsmobile West,.. that they didn't check for their installation error and correct it (or at the very least notify me of the issue) when I had the van in their Fresno shop in 2012 at about 19,000 miles and while I was paying them $3600 for other service and installations. I wonder how many Sportsmobile owners are still driving around with backwards plumbed SMB / Amsoil bypass filter systems, getting little or no oil filtration, and don't know it? If I hadn't had the recent CEL event and stumbled on this great forum looking for answers, I would still be happy and dumb, putting more miles on the rig with a defective oil filtration system. What is the hindsight consensus after several years regarding how bad this situation has been for longivity of our 6.0 L diesels?
'06 Ford 6.0 PSD E350 4x4 RB50 Customized SMB w/penthouse, Aluminess Bumpers & roof playpen. All Diesel & Electric: Espar Hydronic Heat, Wallas Catalytic Hot Plate Stove, VitriFrigo 12v Fridge, Dieselsite & Amsoil Filtration,.. and my other RV is a BMW R1200GS.
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