Big Dawg

I have not yet checked bearings this time around. I installed a newly turned crank .10 under and appropriate bearings last round. I didnt like the look of the last crank.
I still dont think my timming is the problem I'm looking toward the by-pass valve in the oil remote filter adapter I sure hope an 12 dollar part didnt cause me all this trouble.

phughes69

we had a similar problem on a guys car. It was a sbc with a remote mounted oil filter with braided steel aeroquip lines going to it. we had a mobil one oil filter on it and used straight 30 weight for break in on the motor. After running the motor for about 1 hour still using the 30 weight oil the oil pressure dropped to nothing. we changed the oil and filter several times and the same thing happened. What we eventually found was the braided steel lines going to the remote filter were swelling inside. Some kind of reaction between the inner rubber and the oil. we put new lines on it and the problem never came back. So maybe check your oil lines for swelling.

B38

Ditto whats Gary says. I had to cut all big ends and 10/10 crank, my new fricken crank!. resize main caps. Was I stupid. B3

paradigm shift

I would have everthing checked just to be sure. I will probably get slammed for this but the old plastic gage on bearings just to double check clearances has always worked for me in a pinch. Make sure the crank is straight and journals are not out of round. Cam bearings on GenIV can cause low oil pressure. I still do not get why pressure would drop after run a while. Wish I new oil temp. Did you run after letting it sit a while and if so did oil pressure come back up for a while?

I have run with oil by-pass blocked for ever it seems. Just make sure you get some heat in your oil before you zing the throttle if you decide to block the by-pass.

I have seen moisture in the oil cause certain brand filters to clog causing LOW oil pressure but usually not zero after running for a short time.

Let us know what you find out. Good Luck.

SmallPP

I bet you somehow got dirt in your bearings when you put them in. I saw this before on a Pontiac 400 Ram Air III. Oil pressure was good for 2 hours, then only good when cold after that. For oil pressure to be good with a hot motor, the bearing clearances have to be just right. Sounds like hot oil is finding it's way out through the bearings or distributor neck. I say it is not detonation, because that should break pistons and rings first.

Krumbsnatcher

Here is my guess, when you installed the main caps one of them was installed out of the original sequence when they were re-installed thus creating wear and producing heat. Either way those bearings are now toast.

Good Luck.

robyw1

this is what I think it is. you probably have so much air in your oil the pump can't pick it up. there is also a relief spring in the oil pump itself. Perhaps it is hanging open? I don't see any bearing issues here unless you hot tanked the block with the cam bearings in and reusing them. Do you have any oil control or windage device mounted in the pan? you should.. perhaps the engine is tilted in a way that oil runs to the front?

Let me ask you this incase i missed it. Does the pressure ever return after a shut-down and cool-off?

Roby

Big Dawg

Actually I went to the boat this weekend, I removed the dist. and manually spun the shaft to the oil pump. With a manual guage hooked up i got 40 PSI so the oil pump is not clogged and did not fail. so then I start the engine to my suprise I now have oil pressure. 40 psi. but I heard a little knock sounded like a rod pin or sometheng so I pulled the motor did not tear it down yet but when I drained the oil it looked a little dirty for only haveing 2-3 hours on it. could I actually be boiling the oil and losing pressure? why would it take so long to boil and fail 1.5 hrs. running ?
I also replaced the oil cooler at the end of last season could this be the culprit?

B38

Answere is in the teardown, please reply with results.