Thanks Phil , Got to take the cover off to fit the seal, so i'll check the pressure rel at the same time .Must be some way to check the pressure at which the valve opens?. .My compressor can be set up to give a pre determined psi , could try that.
Posted by robert_tuck at Saturday 07:47
In reality... the viscosity of air is negligable compared to cold oil and the respone to air pressure will not coorespond to the way the OPV operates with cold or warm oil.
I know these quite well. I have a test rig for testing oil pumps and I can also test OPV also.The actual operation of the OPV is to "moderate" the over pressure condition while cold and does not "regulate" the engine pressure. Once the pressure gets to the desired pressure point, the valve starts to open. Then it bleeds off oil into the timing chest or in the case of commando it goes back to the pump inlet.
If the speed rises more, the valve opens a bit more, however the pressure rises also. Now the important part...if it were not functioning the pressure rise would equal the limit of the capibility of the pump and I have seen well over 150psi .In a functioning OPV it will start to open (the 3 holes) at 50psi, but pressure WILL still rise to 65-70psi at 6000rpm+. It all depends on the viscosity of oil you use. The thicker the cold oil, the less it can moderate the over pressure condition, since there is only 3 little holes to vent from.In general, once the engine oil is warm, the running pressure never comes that close to even opening the valve at all.Unfortunately I have noticed that VERY few people really get the full concept. Often the suggestion is to go in ignorant bliss, and remove the gauge. Very bad advice in my opinion,The spring tension only counts when the piston is at the point of starting to open the 3 holes. I've tested several OPV and a few suspect items were rusted and found to be nonfunctional.
cheers
Dave
