Ha Ha I guess I should stick to CompD then. No I can't explain one of those cool Opie bypass's. I am sorry I guess my little pressure relief valvethat I bought for $21 tha actually does bypass coolant from th REAR to the FRONT doesn't work. Again I will speak my piece and bYe.

Oh mine is set at 35 to open and it does work.

whats a comp D..................some kinna bomb???

Great avatar for that Whit!

Or he got a D in comprehension?? :humm:

I like it!! Can we have a parts / shopping list?
Only thing I noticed was that with your design (Mainly with the filter being that 'high' in the system) is that valves might not be necessary (At least for filter changes as long as any coolant pressure is released first!).

I thought your 'research' on the summer time heater core bypass was interesting. I had seen others state it was more like a 20F drop or something. If it is only 3F then it wouldn't be worth the price of the valves!! Only thing I noticed on my truck is that there is a big difference between the left vents and the right vents when running the A/C. I think I have something going on in there. There are times that it won't change between the vent position and the floor. Most of the time it does change just fine. A couple of times on her it wouldn't change at all and a couple on me it would wait until I let off the throttle (Kind of like a vehicle that uses vacuum to operate the doors inside the HVAC box).
There have been a few issues with the blend door on these (Dodge) trucks. I wonder if the guys who had bigger temp changes by shutting off the heater core had issues with theirs? That might make a bigger difference in A/C performance then . . . .

Filter head: Coolant Filter Head There's many others out there, but you need one like this with the vertical mounting holes for this application. The only unusual thing is a piece of plate steel to make the bracket. I welded some scraps together, but whatever works. the rest is pretty obvious, bolts clamps, hose, a 1/2" NPT fitting for the head port, and a 5/8" tee for the heater return line.
That's the best part about this design/location - no fuss, no mess filter changes, and no shutoff valves required to achieve that. Plus, it's easy to reach and a very clean install that doesn't block anything else under the hood at all.
That is probably a very good explanation for the A/C-heater issues, dunno. Even Dodge would not have designed it so poorly that simply shutting off the heater core flow was going to result in a dramatic difference in A/C performance.