I just got my 408 rolling again....sounds and runs great...only thing I'm a little concerned with is the 35psi-40psi Oil pressure at idle... how low would it need to go to make you (anyone on this message board) concerned?

Stroker2112

 

What kind of oil are you using? And what kind of pump? Are you sure you did not pinch the O-ring at all during the install? I have a Meling LS2 pump and my cammed car idles around 50psi

 

10w-30 synthetic....ls1 pump w/inlet ported...I forgot to port the outlet...but anyway, I'm sure the O-ring is in right....my previous oil pump idled at around 50psi too.....so the question remains....how low is too low?

 

Whats your idling rpm?

 

That is a good question. What is the pressure supposed to be what range?
Cold start? Idle and WOT
Warm? Idle and WOT

That would be some good info for people to know if the have to much or to little oil pressure.

 

When I rebuilt my 347 last summer on an engine stand with my bearings between .0025-.0030 and a new Katech ported oil pump, my hot idle pressure was ~25-30 using generic non-synthetic 10W30 break-in oil for the first 4-5 oil changes. When I changed to German Castrol 0W30, the hot oil pressure went up to ~35-40psi, and it's still like that through today. I was told idle psi is not as critical as when you're driving and not to worry about it being at 20 so long as normal cruise was around 40psi. Different opinions on how much is adequate at WOT, some say more is better, others say 50psi is sufficient. Others follow the generic rule of 10psi per 1000RPM, others follow the generic rule of 10psi per 100HP

 

I don't know about these new ls style engines, but I always thought the rules with SBC with 7 psi for every 1000 rpms

 

Type of oil can drastically change the pressure. Did you change oil types/brands/weights? Either way 35-40 is more than enough for idle. Also are you seeing 35-40 once its fully warmed up or is that still cold?

 

35-40 PSI at idle is ok. what are you getting at the higher RPM or WOT?.. I would expect at WOT that you should be in the 50+ range. (Warm)

Are you sure your Gauge is correct, are you using a aftermarket one or OEM. Could be the OEM sender is bad ?

 

35 to 40 psi at idle....goes up above 50 at WOT so I guess I'm okay.....thanks for all the feedback and consultation.

Stroker2112

 

Sorry for bringing back an old thread, but...

At idle hot mine is normally around 40 psi, but in stop and go traffic on the interstate for about 30 mins mine continued to drop to about 20 with the clutch in but when I gave it gas it umped back up to 40. After i going again it got back up to 40 at idle?

Any ideas?

 

Not the greatest but sufficient. If it contiues to go down I would try changing the sending unit. The 98's had pump issues so if your a 98 you may want to consider this also.

 

I plan on getting a new oil pump in april when I changed the cam, 99 btw. So as long as it las until then I will be happy.

 

Under 20 I would start to worry a little bit. It sounds like your oil is thinning out though. What weight and brand oil are you using? As long it continues to build as you give it some RPM's and it stays over 20 hot idle I wouldn't worry. Also remember the OEM gauges are not known for their accuracy.

 

buddy of mine drove for a year with 25 psi at warm at idle for a year until he spun bearing

 

60 psi cold start. 35 psi warm idle. 60+ psi freeway.
Edit: mobil 1 10w30

 

If your running mobil 1 oil, it is known to be on the low side of 30 if not the high side of 20. You might try running 0w-40 if you are running mobil 1.

 

mobil 1 fully syn 5w-30, 60 psi cold as well

Why would it dorp tho in stop and go driving?

 

because the engine runs hotter in stop and go.

 

Gm's recomendation that they have told us at service schools is 10Lbs, for every 1000K RPM