The Stovebolt Site Forums The Shop Area Engine Shop oil pressure question v8

307 1970 in a 1/2tn truck,Has 25# at the gauge but no oil to the top end of engine.Could a cam bearing have spun and blocked an oil feed to the lifters or just a really sludged up engine? Ideas and suggestions.

25# hot or cold? Are your lifters making noise? Did this start out all at once? Give a little more information please.

All small block V8's have three full-length oil galleries that run the entire length of the engine, so cam bearings don't get into the mix on top end oiling. Each side gallery feeds one bank of lifters, and the lifters pump oil through hollow pushrods to each rocker arm individually. The center gallery feeds the cam bearings, main bearings, and connecting rods. Remove the pushrods and use a thin, stiff wire to clean out the hollow centers. You've probably got a massive case of sludge that's got the pushrods clogged up. Once you get a little flow to the top end, add a quart of kerosene or Diesel fuel to the oil and fast-idle the engine for about 20 minutes. DO NOT DRIVE THE VEHICLE! The thinned-out oil will flush the oil galleries but it won't have much load-bearing ability.
Jerry

It has been a few years since I studied the oiling on a small block.
I know from working on a 265 a number of years back that all the oil to the lifters and then push rods has to pass through the rear cam bearing.
265's do it through a flat spot in the rear journal, later engines have a groove in the block all the way around the rear bearing bore, so the oil passes behind the bearing to the lifter galleys. I would think the groove in the block could also become sludged up.
Start with the push rods first though as Jerry suggests.

Early 265's had a flat spot on the distributor housing. If it was not clocked properly oil to one cylinder bank would be restricted and the lifters would get noisy on one side only. That problem was corrected about 1958 or so buy putting a groove all the way around the distributor instead of a flat spot. On race engines with solid lifter cams we used to put restrictors into the side oil galleries to prevent filling the valve covers with oil from a high-volume oil pump. That also kept more oil going to the crankshaft through the center gallery.
Jerry

Thanks guys, now I know where to start looking. Don 25# when cold. A friend went through the engine 2yrs ago and put new rings main and rod bearings and cam bearings, then put the engine in a bag and sealed it up and it has sat since then. He gave it to me for a project el camino, I installed it and when running a drill with the primer for the oil never got oil to the lifters/top end of engine. Thought maybe just not enough drill motor, so I started the engine and it didn't get better turned it off.
Was thinking the oil galleys but was also wondering about a feed through the cam bearings. Will start with the pushrods and go from there.

Thanks for the input.

Badly out of adjustment hydraulic lifters will not pump oil through the pushrods. Sometimes it will take a couple of minutes of running to get a steady flow of oil through the pushrods. Be sure the valves are fully closed on each cylinder, then loosen the rocker arm nuts, let the lifters top out, take out the slack with the adjusting nut and continue to turn the nut 3/4-1 turn past the zero-clearance point. Repeat for all 16 valves, one compression stroke at a time.
Jerry

OK, todays exploration of the oil problem has begun. Removed intake manifold,
loosened all valves,removed pushrods and made certain they were clean and clear, all were. Reinstalled pushrods did not adjust valves, installed priming tool and ran drill motor, have #25 at the gauge can see good stream of oil to the gallery on driverside of engine . None on passenger side. Small amount of oil coming up and out of #7 intake pushrod, none anywhere else. Turned engine over several times and same result. I think it's time to begin disassembly of engine to find problem. Do the main and rod bearings get fed from the center gallery that feeds the cam? The little time That I ran the engine it did seem like it was getting tighter, probably good for a boat anchor.
Anymore thoughts?

Thanks

The center gallery has drilled passages that go to the cam bearings, and the oil follows a counterbore around the back of the cam bearings down to the mains. From the mains, drilled passages in the crankshaft lube the rods. I've seen individual rod journals lose lube because of a clogged passage between the cam and the main bearing. That causes one spun main, and failure of the two rod journals that main bearing supplies. The worst "OOPS" I saw involved a race engine crankshaft with a mud wasp nest in one crank passageway. The guy had all the pieces of his backup engine in the corner of his shop, covered up with a tarp. He blew up his engine one night, went back to the shop and assembled the spare in a hurry, and didn't check the oil galleries. The engine had good oil pressure on startup, so he ran it up to 2K RPM to break in the cam. Spun rod bearing! Scratch one $6K race engine!
Jerry

When priming rebuilt Pontiac V8's, I use a heavy duty 1/2 drill, and even it gets hot pretty quick, but it takes that big of a drill to get the oil up to 60 psi. 25 psi oil is not enough for a new engine, look for a missing plug at the galleys.

Joe

Tommy, do you have a distributor housing in place while you're spinning the oil pump? I use an old distributor with the teeth ground off the drive gear as a priming tool, since without it, the passenger's side lifter oil gallery will not pressurize. The housing intersects the oil gallery, and without it in place there will be a massive leak back into the oil pan.
Jerry

I'm using a priming tool that I've had for 20yrs. It's made for this not some cobbled up dist. housing. It has never been a problem before and I have done this many times before. I am using a 1/2 inch drill.I think the guy that gave me the engine has never been this deep inside of a block before ,He said he didn't take the gallery plugs out to clean the gallery. I think in the morning I will pull the engine and disassemble it to find out what the problem is. I really think that the crank journals will be damaged as the engine seemed to be getting tighter the little bit that I ran it. Will report back with my findings.

Since you know all about this, I'll drop out of the discussion.
Jerry