Anyone out there ever see a type 4 engine case with only one oil pressure relief valve?
Thats what I have and I m trying to figure out if its a mistake from the factory or for some reason a mod done on later engines.
The case is from my 76 914 with the serial number of GC 0006666. (The devils case)
As I research this I find they made cases with #of 2915 to 6946 that year. This would make my case number 3751for the year. My cars vin ends in 3729 which makes it number 3728 off the assembly line. So its a good chance its the original engine.
Information I find on another website says that cases with hydraulic lifters had only one oil pressure relief valve and no pressure control valve(the one between the pushrod tubes). The lifters in this engine were the standard solid lifters when I tore it down.
Could have been modded by a PO but everything else looks stock.
Anyone with any information please feel free to chime in.
Thanks

the later blocks... (is it GC?) only have 1 oil pressure relief valve

The biggest oiling failures I have seen in type IV engines is always at the main bearing end farthest from the oil pump. A couple of those were due to the second oil pressure relief valve failing open. Personally, I don't know why they even put that relief valve in the early engines.

I cut an aluminum rod to replace the spring in that secondary check valve, forcing it to be closed all the time. I always thought that somebody should make a replacement fitting to put the oil pressure light switch in that location. That way you would know if the engine lost oil pressure at the rear main bearing. And it would free up the front port for the pressure gauge sender.

Clay

You can buy this rod at EMW.

Ok, I'm stumped...where's the second pressure relief valve? The only one I can picture is the one on the fan end of the engine, bottom side, inside the big slotted screw cap.

I replaced the guts of mine with this: http://www.tangerineracing.com/oilpressurerelief.htm

Discussion here: http://www.914world.com/bbs2/index.php?showtopic=236133

its smaller
I believe.. its a square shaped tool (socket extension)
on the passenger side of the block

Greg,
The valve I am referring to is located between the pushrod tubes on the #1 cylinder. In another case I have from a 74 914 it has a large 12pt allen head screw that holds a smaller spring and piston than the one located near the oil pump. The repair manual I have calls it the pressure “control” valve. And the pressure relief valve is the larger one at the oil cooler.

Thanks for those links Brant. Good info from the folks at Tangerine . From what I can make of all these comments /discussions the pressure “control” valve was eliminated in the later cases like mine. Looks like two reasons for this: first it was pretty much causing the cooler to be bypassed unnecessarily and second : to keep pressure up as the oil warms up.
Seems like a later case like mine without this “control” circuit is a good thing.

Roger, thanks noted...I'll need to look at my three GAs but I think they're all just the ones near the bottom-fan end of the case...