Here is my dilemma. I just finished rebuilding a SBC 350 from a 1977 Vette. The original engine was pretty clean and did not need to be machined as well as the crankshaft did not need any machining. So I used standard bearings, pistons and rings. Used plastiguage on the bearings and all were within specs. I put in a mild cam with new bearings as well. The holes on all the bearings were aligned and everything was torqued and re-torqued. Now I am getting OK oil pressure at the start when the oil is at room temp, some oil comes through the rods with oil priming with the correct priming tool and a good drill, and now as the engine runs, but not much oil. Pressure at start up is over forty on the in car gauge and close to forty on a mechanical gauge on the block by the distributor. As the engine warms, the pressure will state near forty at 2000 rpm's in the car, but drops on the mechanical gauge. At idle the pressure is low around 10. The lifters get noisy as the temp warms as well. The valves were set at zero lash one cylinder at a time, then tuned by listening as the engine ran. The oil pump is new as well. I am thinking three things. One, the bearings have too much clearance, two, the oil pump is bad some how or has issues with the pick up, or 3, one of the welch plugs in the front is leaking. Some how my pressure is not what it should be and the top is not getting enough oil. I am looking to see what other opinions you folks may have, and what step would you take next if you were me.

Here is my dilemma. I just finished rebuilding a SBC 350 from a 1977 Vette. The original engine was pretty clean and did not need to be machined as well as the crankshaft did not need any machining. So I used standard bearings, pistons and rings. Used plastiguage on the bearings and all were within specs. I put in a mild cam with new bearings as well. The holes on all the bearings were aligned and everything was torqued and re-torqued. Now I am getting OK oil pressure at the start when the oil is at room temp, some oil comes through the rods with oil priming with the correct priming tool and a good drill, and now as the engine runs, but not much oil. Pressure at start up is over forty on the in car gauge and close to forty on a mechanical gauge on the block by the distributor. As the engine warms, the pressure will state near forty at 2000 rpm's in the car, but drops on the mechanical gauge. At idle the pressure is low around 10. The lifters get noisy as the temp warms as well. The valves were set at zero lash one cylinder at a time, then tuned by listening as the engine ran. The oil pump is new as well. I am thinking three things. One, the bearings have too much clearance, two, the oil pump is bad some how or has issues with the pick up, or 3, one of the welch plugs in the front is leaking. Some how my pressure is not what it should be and the top is not getting enough oil. I am looking to see what other opinions you folks may have, and what step would you take next if you were me.


Try checking your oil pressure with another mechanical gauge first before you do anything else. You say everything plasti-gauged ok? The clearance on the rods and mains should have been around .0015" to .002". If so, then the low oil pressure is being caused by something else. Are the 3 little 1/2" diameter drive-in plugs at the front of the camshaft in and properly staked so they can't come out? From what you're describing to us, it sounds like one of those little 1/2" diameter plugs behind the cam sprocket has blown out. When I rebuilt my engine in my '82, I tapped those 3 holes for 1/4" NPT pipe plugs so I wouldn't have to rely on those cheap little drive-in plugs. Then I put real short allen head pipe plugs inthe holes.

Try checking it with another mechanical gauge first; your mechanical gauge might be bad (I had it happen to me many years ago).

Try a differant gauge. If your running real thin wt oil like 5w30 running stright 40 or 50 it will help and drill the oil filter adapter by pass for 1/4 n.p.t and plug it that helps a little. You can get the oil pan off C-3s with just lowering the cener steering and ram. I would put a H.V pump in. It will give you like 70 to 80 max and idle at about 40 even after fully warmed up.

sounds like cam bearings to me.did you have new ones intalled? did they put the oil hole up or down? the oil hole should be at the bottom of the cam or oil pressure can change a lot as you described when the engine warms up.

sounds like cam bearings to me.did you have new ones intalled? did they put the oil hole up or down? the oil hole should be at the bottom of the cam or oil pressure can change a lot as you described when the engine warms up.


As the block didn't need any machining, I doubt the cam bearings were changed. Because you normally only change cam bearings when the engine is completely rebuilt. I'm wondering if his oil pump may be shot. It doesn't take very much wear in an oil pump for it to fail in it's job when the oil warms up some.

I recently repaired a 454" engine in my '68. It's oil pressure was very good on startup, but as the engine warmed up, the oil pressure dopped considerably. On teardown I found the inside of the oil pump looked like it had been pumping gravel. Just wiped out inside. I replaced the pump ((about $65) and that cured the problem.

By chance, was the 1/2 inch plug under the rear main bearing cap removed, and not replaced. This cap missing will cause the exact symptoms you describe.