How much oil press is too much?

[jchris]

I recently replaced the cam oil line restrictors with the later small orifice restrictors on my 83 SC per Wayne's engine book. When warm the idle press is about 2 bar and shoots to 4+ when off idle. Is this a typical result? I understand that the 83 SC has 2 high pressure bypasses in the case plus one on the engine mounted cooler, so I believe it is well protected. The oil level is more stable as the engine book said as well as no more chocolate mousse on the oil cap. My question is how much is too much? Additionally I have a case of 20-50 ready for the warmer months, but I'm now a little hesitant to go that heavy (10-40 in it now).

Thanks

Chris
83 SC undergoing the Chinese water torture of restorations.

[schumicat]

the rule of thumb is 1 bar pressure per 1k rpm when oil is warm, so yours is a little high. I would check pressure with a mechanical gauge or put in new sender as 30 year older may not be that accurate. my pressure read little low but totally normal once I replaced sender.

[KTL]

The pressure increase is indeed a direct result of the smaller restrictors. They cut down the oil delivery to the cam spray bars. Just upstream from the restrictor is your oil pressure sender (small can atop your right side cam oil supply line) and that's how it's able to detect the higher pressure.

What the restrictors also do is increase low rpm pressure at the crankshaft part of the circuit, thereby opening the piston jets sooner. This is a good thing because it cools the pistons at lower rpms as compared to them coming on-line at only much higher rpms and somewhat reducing their effectiveness.

The argument against the restrictors is that the cam housing area, including the heads, is receiving less oil. Which is believed to be a bad thing since the heads are the area most in need of oil cooling.

Your oil pressure bypass and relief valves are not engaged until 80 psi (bypass) and ~113 psi (safety valve) so you're not seeing too much pressure at 2 bar (28 psi) or 4 bar (56 psi)

There was a good topic on pressure relief recently posted on the engine forum by 304065

Ultimate Oil Pressure Relief Valve Thread

And when the oil is cold, pressure is much higher. When I fire up my racecar that has previously used a mechanical pressure gauge, it easily hits 100psi and I have to be careful to not work the throttle too hard during warmup (pesky carbs).

[jchris]

Thanks! I'll check it out.

[HawgRyder]

I prefer mechanical guages that are fed by fairly large tubes to sense the pressure.
The result is a guage that responds quicker to changes.
It may upset someone to see the guage acting almost like a tach...but this is what I am used to.
Also..the pressure indication can show you if you have dips in the readings on hard turns (oil starvation) or braking.
Bob