oil pressure in a BN6, too low or okay ?

[bighealeysource]

I know this is a common subject and I have posted questions about it before but still wondering about this subject.

I've read everything I can find out there about what is considered good oil pressure, concerns, worries,etc. Here's what I have going on with my 58 BN6, 6 port head, freshly rebuilt. ANd it's running like a champ, just got back from a two hour drive up and two hour drive back, running 60+ and down stuck in traffic. Temp at 190 with no over heating. Using 20w50 Castrol oil btw. Oil pressure relief valve spring checked and corrected length but have not re-checked it.

When I first start up oil pressure goes to 50+ lbs until it heats up and then will settle down to 40 for about 15 to 20 minutes and then settles down to 25 to 30 at speed and just over 20 stopped in traffic. Ran at the 25 to 30 for the 2+ hour drive back, again running great and sounding even better - who needs a radio with a Healey 6 to listen to! So,do I worry about what seems to be lower than ideal or since it is running great, just drive her ?
Thanks,Mike

 

[Keoke]

! So,do I worry about what seems to be lower than ideal or since it is running great, just drive her ?

Well I would not worry too much although it may be indicative of a slightly worn engine.
,
OTOH, you can boost the hot Idle pressure by shimming the pressure relief valve spring by placing a thin washer inside the cap to effectively "LENGETHEN" the spring.

Reducing the engine's running temperature with cooling system mods will also help-Fwiw--Keoke

 

[twas_brillig]

A bit concerned with the oil pressure in our BJ7 with 65000 miles since new (and about the last 35 years in storage) and a new oil pressure relief spring - just did a 5 day trip and pressure was running about 10 psi per 1000 rpm (eg about 30 psi at 3000 rpm) and would drop to 10 psi at idle; temperatures were in the high 80s and the water temperature about 190F, but cooler temperatures (170F to 180F) didn't really seem to make any difference to the oil pressure.
I think we'll just not worry too much about it, but keep an eye on it. The last 3 litres of added oil were Rotella 15-40; I'll pull the oil relief valve spring and measure it sometime this fall to see if it has shortened itself.
Doug

 

[Keoke]

Doug:

I Was talking to the late Geoff Healey some years ago and he indicated that they consistently ran the engines at 10 PSI per 1000 RPM when hot using UK oil and having it drop to 10 PSI at Idle with no detrimental effects to the engine at all.--Fwiw==Keoke

 

[Bob_Spidell]

FWIW, my BJ8 has always almost flatlined at idle on a hot day and, so far, I haven't had any problems. But, I only have about 90,000 miles on the engine since rebuild (170K total).

Try 20W-50 oil--it should get you a couple psi. There seems to be slight variance in brands due to the viscosity improvers used. I've used mostly Chevron Supreme 20W-50, but will probably switch to Valvoline when I run out of SL.

Also, make sure the rocker isn't spewing oil.

 

[bighealeysource]

Keoke's comment about Geoff Healey mentioning 10#/1000rpm with a warmed up engine works out to exactly what I was running today at 60+mph, about 2500 rpm in 4th gear with overdrive engaged. I'll take it back out tomorrow and check a couple of other comparisons to see how that equation works. If it was good enough for the Healey works, makes me feel good about it !!!
Regards,
Mike

 

[Randy Forbes]

Are you losing any oil through the rockerarm/rockershaft interference?

Anything more than a drip is too much.

My considerable experience with Healey engines has most wear occurring in the top end, not the main, rod or cam bearings.

Keoke: adding a shim to the spring effectively lengthens it :wink: In any event, it does work, but it doesn't take much (or you can burst a spin-on filter__very messy...).

 

[Keoke]

Keoke: adding a shim to the spring effectively lengthens it In any event, it does work,

:shocked:
You know what Randy? you just about right. :laugh:

 

[BobHorvath]

You know I started out with low pressure 10#s @ hot 800RPM and did everything stated above. Rocker re-build, new spring, shim behind the spring, replaced the rod bearings W/O a new oil pump, developed a rod knock, replaced the rod bearings again (this time with a new oil pump)NO CHANGE THROUGH ALL THIS. Finally pulled the engine and the crank and had it re-conditioned. WALA! oil pressure. I am not saying that your situation is the same but the mains is where my problem was. Now 65PSI cold 55PSI hot @ 2500RPM 40#s hot @ 800 RPM. You don't have to re-build the complete engine as I went after the crank with the head still on. I had honed the cylinders, replaced the rings and lapped the valves the year before. .

 

[TimK]

I am lacking understanding of the pressure relief spring function. When cold my engine pegs the gauge at 60 lbs. As the oil heats up (the engine coolant now stays around 175 with my recored radiator and 6 blade fan) the pressure drops to 40 lbs. My question is, why does the pressure relief allow 60 lbs. when cold? but allows 40 when hot? At what point then is pressure relieved? is it at some point above 60lbs? If so, then how can increasing the spring pressure achieve higher pressure than 40 lbs.?? I would think that increasing the pressure relief point would have no effect on a low pressure condition. I hope somebody understands my confusion...

 

[Keoke]

I am lacking understanding of the pressure relief spring function.

Well Tim, we can explain it as a kinda stand off.

We have the pressure from the oil pump which varies as a function of engine RPM pitted against a valve whose closed pressure is established by a spring and a valve seat.

At low engine RPM and low temperature the heavier oil viscosity is sent directly to the engine as the valve is closed
and no oil is bypassed to return to the sump.

At High engine Rpm the valve is forced to open by the higher pressure generated by the oil pump and the excess oil is bypassed by the valve and returned to the sump.

Now you can see the pressure exerted by the pressure relief valve can be modified by shortening the spring or lengthening it.

When we LENGETHEN it by adding a shim we cause the oil pressure in the system to rise at Idle or at higher engine speed because it takes more pressure to force the valve open.

---------OK NOW----Keoke

 

[twas_brillig]

When you first start the car on a coldish morning, the oil can be quite viscous and flow poorly. The pressure relief spring holds a metal relief spring cup up against a face within the block (a metal to metal seal) and if pressure exceeds a certain level (presumably 60 psi in your car), then the cup is lifted off the seat and enough oil bypasses the engine's lubrication system and bleeds back to the sump to prevent overpressuring the rest of the system. Where we seem to run into problems is that if the spring weakens, then that metal to metal seat passes more and more oil, at lower and lower pressures.
There's some discussion regards oil relief spring lengths etc. in these two threads: https://www.britishcarforum.com/bcforum/u...RING#Post519075 and https://www.britishcarforum.com/bcforum/u...f_Va#Post531756
Doug

 

[BobHorvath]

Here is another way of stating the significance of the relief spring. Cold oil is viscous and the sloppy clearances do not have quite the impact as when the oil is hot. The spring and buy-pass orifice are designed to relieve pressure over a certain amount of oil by-pass around bearing clearance. when the clearances go beyond the range of the spring/ orifice design the system has no affect (fully closed. Strengthen the spring insert a spacer, weld the by-pass shut if you like but the sloppy clearances provide so much by-pass with hot oil the result is low pressure period.

 

[TimK]

Thank you Bob. Your explanation makes sense to me. Thanks to Keoke and Doug for trying. I actually have a new spring, but didn't want to bother with trying to install it if I didn't understand why it would make a difference.

 

[Randy Forbes]

This is a quite worn spring and valve being removed from a BN4 block; the 3000 is identical. The wear on the valve cup is obvious, the wear on the spring is on the sides of the coils, from rubbing in operation, presumably.

The new valve will have to be lapped into the seat (dressing the seat) to function properly.

 

[nicko]

Hi all I think I may have the opposite problem oil pressure to height . From cold start I get 60PSI which after warming up settles down to 40PSI. On a run at 3000rpm I have about 60PSI but it will rise above this up to 80PSI .Is this normal? The car is running great at the moment and has had a fresh oil change this year (20W50) I don't use a lot of oil but still have to top it up regularly.If it is to height what could be the cause of this?
thanks nick

 

[Keoke]

Two things come to mind Nick:

1] the pressure relief valve spring may be hanging up in it's bore.
2] The oil pressure gauge may be defective.

---------------------------Fwiw--Keoke

 

[RonMacPherson]

My 2 and half cents worth(inflation, you know).

If you are not running 20w-50 and your pressure is lower than you like. first thing switch oil...

Smokey Yunick(who I consider to be one of the greatest auto engine men ever) stated oil pressure standards for him were 10 psi for every 1000 rpm.. Oil volume is much more important than oil pressure. Anything over 80 psi is basically excess pressure on a pushrod equipped engine.

There was a thread on one of the other forums(think it was MG0 asking about what to do, how to drive to get the car home. Advice was given to keep the rpm's up.. Actually what you want to do is keep the vacuum up.. That lessens the load on the bearings and other lubricated components.

So if you are ever in a situation when your oil pressure drops and you need to get home, if you have a vacuum gauge, drive it with the highest vacuum reading possible.

 

[TimK]

I'm surprised no one suggested an oil cooler. Wouldn't that be the answer for hot oil? Does anyone have any advice on a cooler?

 

[Randy Forbes]

On cue...