New overhaul on a 350/350hp SBC after a cam lobe went flat, and some other lobes were "on the way": New bearings, new cam & lifters, new springs, rings...but old oil pump. I plasti-gauged all mains and rod bearings, and they were all in spec.

Run-in of the cam was done at 2500-2700 rpm for about 35 minutes. Oil pressure was at 40 psi. (Rotella 15-40 T + a pint of the Comp Cams break-in oil additive)

Today, I fired it again and let it run at about 1500 rpm until up to temp, and then set idle at about 1000 rpm to adjust the hydraulic valve lash. The under hood (aux oil pressure gauge) was reading about 17 psi. IF I blipped the throttle (just a quick "soomaaaah!") it would zip to about 35-40 and then down to just under 20.

No babbit anywhere - a good thing. But, what should the oil pressure be, keeping in mind the engine is "hot" and idling?

In any case, I bought a new Melling High-volume pump, and since dropping the pan doesn't look like a major undertaking on a '69, I'll prolly install it if for nothing else but peace-of-mind.

I know...A long way around the barn to get to my question: Is 17 PSI on an engine that is up to (approx) 170ºF normal for a SBC with a standard pump?

What do you think? I'm thinking I'll change the filter and then see what happens. If pressure doesn't come up, then it is time to drop the pan, I recon!!

P.

 

If the pump is a stock Chevy unit, then the 17 psi at idle is a bit higher than most. GM designed it with a "10 psi per 1000 rpm" concept. An idling engine doesn't need a lot of oil pressure (as long as it flows to all locations requiring it). But if you have significantly higher spring/tappet loads in the valve train, it won't hurt to install the Melling pump. It will use more HP than the Chevy unit, but it may also give you more 'peace of mind'.

 

BUT! It is U sir that gives me a bit of that peace of mind. Ya see I had failure on a new rebuild many moonz ago, and oil pressure was one clue I was in trouble. Course the babbit in the low spot and in the pan was a "hint" too. However, I drained the oil in preparation for putting on, as you say, a "piece of mind" Melling (high-volume) pump, and there is NO babbit or metal stuck to the magnetic oil plug (that surprises me some) either. I think I'm OK (as in it is a stock pump, far as I know), and there is no signs of the little beast chewing itself to pieces (a GOOD thing!). Thanks very much for your response.

P.

 

 

I dropped the pan (simple on a 69) this morning and changed the pump for a high volume (Melling) unit. Works like a charm. Now at 750 rpm idle it is running at almost 30 psi (up from 17 before).

BTW...It runs very well. Went out to seat the rings - did (4) 2k-4k 4th gear WOT pulls. It is going to be a very sweat L46 (350/350+).

Thanks for your help! I do now have that piece of mind you mentioned earlier, and that is a good thing!!!

P.