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Oil Pressure Relief Valve

T

Tom H

Platinum Level Sponsor
I think I am still having problems with my PRV. Never have seen it stuck after I remove it to inspect, but always I get better pressure after I remove it and look at it!

I see in the Production Changes" list that a Pressure Relief Valve change was made in April 1967. Can someone tell what was changed. - what does an older one look like and what does a newer one look like? Are they interchanegable or did the filter block also change?

Thanks,

Tom
 
Alpine 1789

Alpine 1789

SAOCA President
Diamond Level Sponsor
The valves are not interchangable as you have to match the oil filter base to the valve. I don't have a photo of the later one handy, but there is picture of three different valves in the old Tiger Tom article on making the valve adjustable: http://teae.org/relief-valve-change-can-cure-alpine-lop/. I am sure someone will correct me, but I believe the later valve looks like the one in the middle.
 
Robbo

Robbo

Donation Time
Kelly, is this what i'd find on the engine from you? If so, how and when would you recommend i adjust?

Rob
 
RootesRooter

RootesRooter

Donation Time
The "change" that was made per a Rootes technical bulletin, was to return to the PRV part number used on Series IV, because the Series V PRV's became prone to sticking open. (Removing and cleaning them in solvent may cause them to function normally for a short time, but they always act up again.) These two PRV's use the same base and look identical, tho the Series V must have a stronger spring, as operating psi is 5lbs higher.

The different design mentioned is the change in design used in the later, Arrow/Hunter Range. Those later PRV's are steel instead of brass, fatter, and with the threads at the opposite end of the valve from the previous design, like the "middle one" shown in Jim Stone's photo.

Later, NOS PRV's show up occasionally on eBay, but no parts suppliers I know of currently stock them. The matching bases are easier to find, from owners of junked Alpine fastbacks.


Tom H said:
I think I am still having problems with my PRV. Never have seen it stuck after I remove it to inspect, but always I get better pressure after I remove it and look at it!

I see in the Production Changes" list that a Pressure Relief Valve change was made in April 1967. Can someone tell what was changed. - what does an older one look like and what does a newer one look like? Are they interchanegable or did the filter block also change?

Thanks,

Tom
Click to expand...
 
G

Giacomo71

Donation Time
Last year i rebuilt my 1725cc engine, with a new oil pump. 1 race later i was on the bench again with a disintegrated shell bearing. The fauly all goes to LOP. last week we rebuilt the engine again and wanted to takle the LOP problem. after reading most of the articles in this site my mechanic decided to try our way of increasing the oil pressure. what we did was change the spring inside the vale and BOOM 100psi when reved and 30 psi idle. All the expences i did where all because of .70cents spring.
 
A

agmason54

Donation Time
Tom,
I have several. One has your name on it- base and all for free.(46,000 miles)
happy fathers day.I owe ya one...
AGM
I had one act up once. If you floor until the valves float it usually clears itself....
 
alpine_64

alpine_64

Donation Time
Giacomo71 said:
Last year i rebuilt my 1725cc engine, with a new oil pump. 1 race later i was on the bench again with a disintegrated shell bearing. The fauly all goes to LOP. last week we rebuilt the engine again and wanted to takle the LOP problem. after reading most of the articles in this site my mechanic decided to try our way of increasing the oil pressure. what we did was change the spring inside the vale and BOOM 100psi when reved and 30 psi idle. All the expences i did where all because of .70cents spring.
Click to expand...


I;d be worried about 100psi in an alpine motor. Have you pinned the bearings? I believe several of the race guys will probably chime in, jarrid, andy? But IIRC with to high oil psi the bearings an be floated. Another thing is that a stock good condtion OPRV will give you 30psi at warm idle.
 
T

Tom H

Platinum Level Sponsor
Al, thanks - I may take you up on it. I'll be in touch.

Rootes and all, Thanks for the replies. But I am still confused a bit. My PRV has the thread just under the hex head, seems to be brass, and has a steel piston inside.

Is my steel piston device the latest version Rootes used in the Series V, and is it then the least llikely to stick? Or is one of the other versions better, and less likely to stick? Is it likely that my valve sticks only when hot? When I hold it in my hand and try it, it seems perfect. If the valve is not sticking I may have a more serious problem, but I think it's the valve.

I think I will make an adjustable one, so when it seems to be sticking I can at least turn the adjust and see what happens.

Tom
 
C

Chuck Ingram

Donation Time
Tom

Be sure to increase the pressure slowly.
I did this many yeras ago.Unfortunately I had it screwed in all the way

WHAT A SURPRISE when the oil filter blew a couple of seconds after starting the engine
 
G

Giacomo71

Donation Time
Thanks for you answer. What do you mean pinned? I had new standard crank and con rod bearings and oil pump and this year i changed the spring of the OPV and the pressure went up. the pressure at idling is at 30psi and 100 at start and reved up. after a few minutes the pressure goes down to 70 psi when reved up and remains around 30 at idle. do you think there is a problem. My mechanic told me that since the oil pressure drops down from 100psi to 70 im safe. I must also tell you that i increased the compression to 11 and he belives that with the work he has done to the head and othere things he increased the bhp with at least 45bhp. That is why i need good oil pressure.
 
A

anduril3019

Donation Time
I used to build Lotus Twin Cam engines. For our shop's mild race engines (150-170 hp @ around 7000 rpm) our rule of thumb was to shoot for 10 psi of oil pressure for every 1000 rpm. ie. 30 psi @ 3000, 60 psi @ 6000, etc. Of course every engine is different, but what does anyone think of these numbers for the Alpine?
 
R

RootesRacer

Donation Time
Well folks like to put higher oil pressure for higher loads and RPMs, but you guys need to keep in mind that there is a roll pin that transmits the torque to the pump and you might want to put more and better pins on the pump drive gear.
Also the cam drives that gear and if you double the pressure you will also double the load on the gears.

I run 70psi on my engine and if I felt I needed more than than I would run an external belt drive pump.
 
kmathis

kmathis

Donation Time
Ken Ellis said:
Kelly, was your modification based on the Tiger Tom article that Jim mentioned, or some other method?
Click to expand...

There is someone here on the board that gave me the detailed instructions on what to do; I can't find it just now, but it is close to the Tiger Tom article. I didn't unsolder the brass tube; I drilled out the bolt part until the spring and all popped out and then had an adjustment nut made and the other brass piece that the spring sets into; a local machine shop did the work for about $75.
 
kmathis

kmathis

Donation Time
Robbo said:
Kelly, is this what i'd find on the engine from you? If so, how and when would you recommend i adjust?

Rob
Click to expand...

Hi, Rob:

Yes, you do have the modified valve that I had made; adjust the outter bolt clockwise for higher pressure and vice versa. It was a real problem when I first got the car, so that was one of the first modifications that I did.
 
Alpine 1789

Alpine 1789

SAOCA President
Diamond Level Sponsor
Tom: I am fairly certain the valve with the brass tube is the next-to-last design, the one that was replaced late in the SV line. The problem is that the steel piston can score the inside of the brass, which is what leads to the sticking. The other designs were all steel.
 
R

RootesRacer

Donation Time
Tom H said:
Here's the specific detailed article on making the adjustable PRV:

http://www.team.net/www/rootes/sunbeam/alpine/mk1-5/techtips/prvalve.html

But I'm still looking for an answer to my question :

Is my PRV, with threads just under the hex head, with brass body and steel piston the latest SV design? And is it the least likely to stick?

Tom
Click to expand...

Thats my writeup, it used to have my name on it but looks like it was dropped.

Personally I think all the years pressure valves are flawed in that they used a steel bucket instead of a brass or softer metal one.

If I had a better lathe (one that cut threads) I would make a bunch of valves for us all.

In any case Any of the relief valves can have the mod done to them and if you carefully deburr and hone the ID of the case, you can have a bucket made that is a close fit and wont batter the inside bore and eventually hang on a burr of its own making.

Just sayin...
 
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