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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: dumbucket1 on November 30, 2007, 02:17:26 pm

Title: Low oil pressure, maybe cam bearings?
Post by: dumbucket1 on November 30, 2007, 02:17:26 pm

I bought a 350 from a guy he said he put new rings and rod/crank bearings in it. The only bearings he did not change were cam bearings. The motor still goes to zero oil pressure when the engine is warmed up. Do you think the cam bearing would cause this? Yes more than one oil pressure gauge was hooked up to verify the zero pressure reading. Thanks

Title: Re: Low oil pressure, maybe cam bearings?
Post by: d stroud on November 30, 2007, 04:12:37 pm

I don't think the cam bearings would cause zero oil pressure. 

What is the pressure at when cold?   I definatly would not run it again until I found the cause. 

Title: Re: Low oil pressure, maybe cam bearings?
Post by: VileZambonie on November 30, 2007, 04:13:15 pm

Well since you are certain the gauge reading is correct I would check the clearance in the pump. Does the engine knock? Where did you tap in for oil pressure? You have near the distributor and near the oil filter. Check at both places...

Title: Re: Low oil pressure, maybe cam bearings?
Post by: dumbucket1 on November 30, 2007, 04:34:21 pm

checked at near distributor. When the motor is cold pressure is at 40 psi the drops as it warms up. Pressure goes up and down with rpms after warmed up. There is an ever so faint knock starting or what sounds like a knock but its only there after warmed up.

Title: Re: Low oil pressure, maybe cam bearings?
Post by: DnStClr on December 01, 2007, 12:47:58 pm

Does the 'check engine light' come on? What weight oil are you using? A heavier weight oil may be needed, like 20w50. Unless the engine is knockin and smoking of course, which is a real bad sign.

Title: Re: Low oil pressure, maybe cam bearings?
Post by: VileZambonie on December 01, 2007, 01:02:58 pm

check at the lower oil galley tap too. The distributor body allows feed the oil to the upper galley. If you still have low oil pressure pull the pan and check the clearance in the pump and for all of your main and rod bearings. If it has high miles save yourself the aggrivation and just pull the engine and give it an overhaul.

Title: Re: Low oil pressure, maybe cam bearings?
Post by: dumbucket1 on December 01, 2007, 03:10:39 pm

Ville, I pulled the pan and guess what? the pickup tube was sitting on the bottom of the pan had fallen off the oil pump...kinda strange huh? Probably just ought to rebuild again as a precauction right? The motor is not in a daily driver.

Title: Re: Low oil pressure, maybe cam bearings?
Post by: VileZambonie on December 01, 2007, 09:23:14 pm

LOL deja vu! I just built had one the other day same deal. Yeah odds are the bearings are pretty beat. Pop the #1 main cap off and look at the bearing. If it looks beat just overhaul it. Once I set the pickup in place I always use a cold weld like JB weld to hold the pick up in place. Don't ever braze or weld it on. Good luck man

Title: Re: Low oil pressure, maybe cam bearings?
Post by: 1976Scottsdale on December 02, 2007, 05:06:17 pm

Did that too.  Same pressure reading.  Roll in new bearings and a new pickup tube.  Be good to go.