bearing knock and good oil pressure

[Walter F.]

Can you have a bearing knock and GM acceptable oil pressure at 10 pounds for every 1,000 RPMs.

[Joe R.]

Re: bearing knock and good oil pressure

Yes, but has the pressure dropped from what it was before the knock. If it's a rod bearing and you continue to run the engine it will drop to zero.
Don't wait!

JR

[Terry D.]

Re: bearing knock and good oil pressure

I've had a wrist pin knock that sounded like a bearing knock, but whatever it is it needs fixed sooner than later! Are you sure it is coming from the bottom end?

[Phillip M.]

Re: bearing knock and good oil pressure

I bought a new 1969 Chevelle Malibu equipped with the 307 engine & auto. trans. Had to have GM replace the block at 3,000 miles due to main bearing knock. Problem developed slowly and was particularly noticeable pulling up a hill under low rpm load. Never had the oil pressure idiot light come on. So, to answer Walter's question, yes it is possible.

[Tom L.]

Re: bearing knock and good oil pressure

I had a knock a few years ago, turned out to be a bad lifter. Twice, fortunately no damage to the cam.

[Duke W.]

Re: bearing knock and good oil pressure

Could be a bearing, wrist pin, or piston slap. More info is needed. Is it more noticeable hot? Cold? Load sensitive? Engine speed sensitive?

Duke

[Leif A.]

Re: bearing knock and good oil pressure

What is your oil pressure at 3000 RPM under load??

[Walter F.]

Re: bearing knock and good oil pressure

Mostly when first started. i would say it has been doing this for about 6,000 miles or more. Never gets any louder. Oil pressure at 30 mph is about 30 pounds or more. At 50, 50 pounds. It never goes over 50 pounds, ever This is a 84, so it has the digital dash which was just rebuilt so it is accurate. car has 153,000 miles, all original. It also has a new oil sender. On hot days it drops to 11 in drive and the knock is not heard. Using 10-30 Mobil 1.

[Duke W.]

Re: bearing knock and good oil pressure

If you are saying the noise goes away as the engine warms up (The circumstances are still not clear to me.), then it's likely piston slap. As long as you warm it up easy and don't place the engine under heavy load until the noise goes away, it likely will cause no harm.

Normal oil pressure is a function of engine speed, regardless of load, not road speed. Check the AMA specs. Most sixties small blocks are speced at 40-45 psi @ 2000 hot other than late '63 and later mechanical lifter engines, which are about 55-60. GM did not specify idle oil pressure, but SHP engines usually show higher idle oil pressure due to the higher idle speeds than base engines.

In later years some GM engines have lower volume oil pumps that usually reduced idle oil pressure, but anything over about 10 psi at 500-700 should be okay as long as the hot spec at 2000, or whatever, is achieved.

Unless your engine has a roller cam (The first year for OE roller cams slips my mind, but I think it was '87.) I suggest you ditch the SN-spec 10W-30 Mobil 1 and use 15W-40 CK-4, It's best for any vintage engine with a sliding surface valve train.

Duke