Mechanical OP gauges? Which make?

[Brit33]

Looking for a better OP gauge as mine appears to be non-linear at lower Oil pressures. (to be confirmed - suspected).
Orlan Rober current.



Would like a Racetech gauge but just a bit pricey.
Smiths?
Auto Meter?

Any recommendations for accurate mechanical gauges especially at low pressures?

 

[dparm]

Any reason you are set on mechanical? There are some pretty awesome digital "multi-purpose" gauges that can show you many things.

 

[Brit33]

Originally Posted By: dparm
Any reason you are set on mechanical? There are some pretty awesome digital "multi-purpose" gauges that can show you many things.


well just always been a believer in the mechanical gauges. got the tubes set up and as I have 'alfa romeo' electrical gremlins I try to steer away from anything electrical! lol

I had a cheapo electrical one from the same make here but I preferred how the mechanical needle responded also.

 

[440Magnum]

I also prefer mechanical gauges for OP. On the affordable end of things, I've had good results both with Sunpro and Equus. You can spend a lot on VDO liquid-filled with all the bells and whistles, but the pressure guage is an ancient technology- they can even mass-build them pretty decent in China these days ;-)

Here's a video of the Equus (made in China) I put in my Ram a year or so ago:

 

[Brit33]

Originally Posted By: 440Magnum
I also prefer mechanical gauges for OP. On the affordable end of things, I've had good results both with Sunpro and Equus. You can spend a lot on VDO liquid-filled with all the bells and whistles, but the pressure guage is an ancient technology- they can even mass-build them pretty decent in China these days ;-)

Here's a video of the Equus (made in China) I put in my Ram a year or so ago:





but in the older times they were all calibrated.
with such mass production there will be inevitably gauges with inaccurate readings.

mine will show 10 psi at 900m rpm hot idle
step on the gas to say 1200 rpm and it will shoot up to 30+ psi.
40 psi @ 2200 rpm
50 psi @ 3200 rpm

for me this is not linear under 30 psi
(maybe the design of the oil pump I don't know yet)

 

[440Magnum]

FWIW, use copper capillary. The plastic capillary tube is probably fine- when I was young and naive I used it for over 100k miles without a hitch. But copper is safer. Slide some slightly larger vacuum hose over the copper to keep it from rubbing/rattling, and also to prevent funny engine noises from being carried up the copper to the gauge.

 

[440Magnum]

Originally Posted By: Brit33
Originally Posted By: 440Magnum
I also prefer mechanical gauges for OP. On the affordable end of things, I've had good results both with Sunpro and Equus. You can spend a lot on VDO liquid-filled with all the bells and whistles, but the pressure guage is an ancient technology- they can even mass-build them pretty decent in China these days ;-)

Here's a video of the Equus (made in China) I put in my Ram a year or so ago:





but in the older times they were all calibrated.
with such mass production there will be inevitably gauges with inaccurate readings.

mine will show 10 psi at 900m rpm hot idle
step on the gas to say 1200 rpm and it will shoot up to 30+ psi.
40 psi @ 2200 rpm
50 psi @ 3200 rpm

for me this is not linear under 30 psi
(maybe the design of the oil pump I don't know yet)


Oh, engine oil pressure is DEFINITELY not linear with RPM. Don't ever expect that! At low RPM, the clearance leakage so totally dominates, then it goes through a transition where the pump keeps up or gets ahead and pressure is linear for a while, then it hits the pressure relief valve.

 

[Brit33]

Originally Posted By: 440Magnum
Originally Posted By: Brit33
Originally Posted By: 440Magnum
I also prefer mechanical gauges for OP. On the affordable end of things, I've had good results both with Sunpro and Equus. You can spend a lot on VDO liquid-filled with all the bells and whistles, but the pressure guage is an ancient technology- they can even mass-build them pretty decent in China these days ;-)

Here's a video of the Equus (made in China) I put in my Ram a year or so ago:





but in the older times they were all calibrated.
with such mass production there will be inevitably gauges with inaccurate readings.

mine will show 10 psi at 900m rpm hot idle
step on the gas to say 1200 rpm and it will shoot up to 30+ psi.
40 psi @ 2200 rpm
50 psi @ 3200 rpm

for me this is not linear under 30 psi
(maybe the design of the oil pump I don't know yet)


Oh, engine oil pressure is DEFINITELY not linear with RPM. Don't ever expect that! At low RPM, the clearance leakage so totally dominates, then it goes through a transition where the pump keeps up or gets ahead and pressure is linear for a while, then it hits the pressure relief valve.



ok good to know.
maybe due to the old alfa leakages we get this notoriously low pressure at idle.
the alfsud manual says 5 psi min! almost nothing.

future project is to have the crank reground for tighter clearances.

 

[Brit33]

I see the manual for the 16v version of my engine says 0.8 bar idle OP. around 11 psi.
Mine is the 8v version (2 cams and 8 tappets instead of 4 cams and 16 tappets).
Haven't found info on mine yet.

 

[Trav]

Originally Posted By: Brit33
future project is to have the crank reground for tighter clearances.


Don't go too tight though some of these old engines had a lot of crank/block flex, when you tighten them up the crank can hit the bearings when it flexes under high revs.
Oil volume is good even with the lower pressure, they don't need high oil pressure to stay together.

These engines sling a lot of oil all over the place like a small engine that uses no oil pump at all.

 

[Brit33]

Originally Posted By: Trav
Originally Posted By: Brit33
future project is to have the crank reground for tighter clearances.


Don't go too tight though some of these old engines had a lot of crank/block flex, when you tighten them up the crank can hit the bearings when it flexes under high revs.
Oil volume is good even with the lower pressure, they don't need high oil pressure to stay together.

These engines sling a lot of oil all over the place like a small engine that uses no oil pump at all.


Very true. I did hear that these boxer blocks do flex a lot.
Makes sense.

Reassuring what you say about the oil flow.
Thanks

 

[OVERKILL]

I've always had good luck with AutoMeter gauges and they aren't insanely expensive.

 

[default]

I've used the Summit Racing house brand gauges with success. Good suppport, got a bad temp gauge in a kit and they mailed out a whole new kit.

 

[Brit33]

Thanks for the advice guys.
Got some options there.

Maybe the auto meter but not sure if its going to be any better than the budget one I have now.

I will sleep on this one.
*just got stung by customs yesterday by importing a water pump and timing kit into the country! some get through some don't
60% import tax plus admin commission!!!!!!!

 

[440Magnum]

Originally Posted By: OVERKILL
I've always had good luck with AutoMeter gauges and they aren't insanely expensive.


Agreed- I forgot to mention them. I'd consider them "mid grade" gauges between stuff like Equus and Sunpro on the low end and VDO on the upper.