BT7 oil pressure relief valve

when i redid my engine i did not replace the valve cap. at the time i was reading a story of someone who had gotten a new one only to have issues. mine looked pretty good so i went with it. i did replace the spring and washer.

recently i have noticed my gauge reads over 60 psi when i first start the engine. this was not the case up until now. it would never go above 60. so i wondered if the head was maybe sticking or something. it is hot and the parts are cheap so i ordered a new head, spring and washer.

put them in and took a ride this morning... early. did i mention it is hot here? seems to be a common theme lately.

anyway when i fired it up this morning, my gauge went up to about 65psi when driving. of course it came down as the engine got hot. now this could be a gauge issue seeing how both valves were reading high. i did check the gauge before with another gauge and it was pretty close. but maybe it has decided to adjust itself a little...

also i noticed the new spring i got this time was about a 1/16" longer than the new spring i got last time. Hmm, both from Moss. maybe the old one compressed some while in use????

none of this may be an issue and i am fine leaving it alone. i really just wondered at what point should i be concerned. i don't think 65 psi is probably a big deal if that is as high as it goes, assuming it is not the gauge. but i wondered what you all think.

while i was changing the valve i did try to clean out the valve seat in case it had something causing it to stick. think i got it pretty good. i certainly did not feel any issues putting in the new head.

Thanks
TL

TL,

As I understand the system, the design of the relief valve is to regulate the pressure by “kicking in” at 60 psi. If you don’t go above 65 psi, I don’t think you need to worry. The gauges all have precise accuracy issues and it could be the reading of 65 psi is actually closer to 60 psi.

I had low oil pressure until I rebuilt my engine. Turns out the biggest loss of pressure was due to worn cam bearings. When I ran the engine after rebuild, my gauge would go up to around 100 psi when cold and drop to 60-70 psi when the engine and oil were hot. After a lot of fault finding, I descovered the “cap” as you describe or bullet head in my relief valve was actually from a 100 engine which is incorrect for a 100/6 or 3000 engine. I have attached a photo to show the one on the left is wrong and the one on the right with the recess at the shoulder is correct for our engines.

Once I replaced the valve bullet head with the correct item, my pressure now reads 60-65 psi when cold and also when driving regardless of the engine/oil temperature. When the engine is hot, I have 40-50 psi (usually steady at 45 psi) at idle.

The length of the spring can have an affect on the pressure, however I think 65 on the gauge is not a problem.

What pressure do you have at idle when the engine is hot?

Cheers
Tony

tony
the one on the right is what i had and what i got new. So the bullet is correct. my old bullet head showed some wear around the outer edge and around the bevel edge. No idea how many miles it had on it.

when hot, my engine used to run 20-25 psi at idle and a little over 40 around 2500 rpm. today i am not sure i ran it long enough to really get it hot. probably only about 10-12 miles. when i got home the idle was a little over 20 and it was at 50 psi around 2500 rpm.

i need to run it a little longer, i think, to be sure what i have got now.

i did expect my psi to be a little lower than average. when i plasti-gauged my bearing gaps they were all at the high end of the spec for both main and rod bearings. not above spec but at the high end. well as close as you can tell from plasti-gauge anyway.