Oil Pressure/Clattering issues

[scoutcamper]

Hi All,

Some backstory: Steve Van Gent and I(his son) have been building up my 71 stepside for about 2 years now. I was able to track down a "donor" 72' long bed that had a working no-issues 350. When we pulled it out of that 72 we painted it, changed to edelbrock elite series valve covers, put a edelbrock 1406 performer carb on it, and new spark plugs and distributor cap(non-hei), we also picked up a 700r4 trannie that we had rebuilt by the local(reputable) trannie shop. Pics here: http://67-72chevytrucks.com/vboard/s...d.php?t=459267

The engine now in my truck has an interesting problem. When it is cold it has lots of oil pressure, but once it warms up the oil pressure drops to zero. You can get the oil pressure back up by stepping on the gas. The other odd issue is that when it is in Park or neutral(no load) and you rev the engine at all you can hear clattering.

Thoughts? I have been told that this is not a big deal and that the SBC will run forever anyways.

Thanks,
Matthew

[geezer#99]

What you got for a gauge?
Stock electric or mechanical!

[GMCJOE]

Usually when you have a oil pressure drop like that after it warms up, it means you either have a bad oil pump or the bearings are worn. If the oil pump is not pushing the oil after it warms up, the result will be engine clatter. If the main bearings are worn, loss of oil pressure and clattering. It could be a combination of bearings. Main bearings are the first place the oil passes thru before heading up thru the rest of the engine. The last place the oil passes thru before you get your oil pressure reading is your cam bearings. The rear cam bearing is what gives you the oil pressure reading via the sending unit. But if the oil fails to get that far, you won't get a reading.

Pull the oil pan and check to see if your main bearings are shot. If not, replace the oil pump before doing any damage to the engine if none has been caused yet. It sounds to me like the oil pump is failing and can't push the lower viscosity of the oil after warm up.

[shawno72]

I was told that is normal with a stock gauge.

[GMCJOE]

It might be normal on a stock gauge. But if the result of the drop in oil pressure is the engine clattering, that's not normal and will cause internal issue.

[geezer#99]

It might be normal with a stock gauge but get an accurate mechanical one to confirm no or low oil pressure.
And don't go tearing any motor apart without a bunch of diagnoses. Maybe his clattering isn't even oil pressure related. Saves time and especially money.

[GMCJOE]

That is true, assuming it is a stock gauge you should use other means to read the oil pressure. The oil pressure and clattering could be 2 separate issues.

[shawno72]

Originally Posted by GMCJOE

It might be normal on a stock gauge. But if the result of the drop in oil pressure is the engine clattering, that's not normal and will cause internal issue.

True at idle my engine purrs like a kitten with zero noise so mine is probably an inaccurate gauge....I hope

[GMCJOE]

Give us more information on what kind of gauge is used? Electric or mechanical? Does it clatter before the drop in oil pressure or after?

[scoutcamper]

The gauge is Mechanical Factory Stock. It clatters at any time high or low oil pressure when you apply throttle with no load(park or neutral)

[scoutcamper]

I did put straight 50W non-synthetic oil in about a month ago and still the problem's remain.

[GMCJOE]

The factory is electric. I suggest putting a oil pressure test gauge on and test it. Have you ever had the distributor out? Or have the rocker arms off?

Where does it seem that the clattering noise is coming from?

[scoutcamper]

I have had the distributor out. The clattering noise comes from the valve covers, im not brave enough to run the engine with the valve covers off.

[SnS C10]

My stock gauge works perfectly. I have never seen one do what your describing either. Sounds to me like your oil is not getting to the gauge due to worn bearings. Thats why u have a reading when its cold, the oil is thicker on startup. As for the noise.....low oil pressure and a clattering or knocking noise? I would bet that they are related and would check the bearings
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[GMCJOE]

Ok, I would check your timing with a timing light. Won't solve the oil pressure issue. If you aren't getting enough oil pressure to the rocker arms, you will have clattering. Check the pressure with a gauge and let us know what the pressure really is. You may be in need of a rocker arm adjustment if you got runnable oil pressure.

[scoutcamper]

I am beginning to wonder if this is all connected to the distributor, in theory if we did not plunge the distributor correctly the oil pump could not be properly connected and then the timing being off *could* cause the clattering, yes? I will check the timing but other than the obnoxious clattering the engine is running like a dream so it seems unlikely to be a timing issue.

[GMCJOE]

If your distributor is mounted flush with the intake, no gap, it is correctly lined up with the oil pump. Being out of time could cause valve lash. But I would definitely put a oil pressure gauge on and test it. If it runs at least 10psi idling and increases under throttle, it is acceptable and just means you have normal bearing wear. At that point I would suggest you do a rocker arm adjustment. You can do this without the engine running. I will look up a link and provide it to you. Pretty simple.

[geezer#99]

Clattering could be several things.
Detonation.
Broken rocker seat.
Collapsing lifter.
Rocker stud pulling out.
Rocker nut loose or backed off.
Before you pull the covers take a 3 foot long piece of old broom handle. Put one end behind your ear and put the other end on various spots on your motor. You'd be amazed how easy it is to narrow down the source of a noise.

[GMCJOE]

Alright, I can't find a good link for you, as I used a Chilton's manual to do mine. So I will just explain the adjustment for the rocker arms. First thing you should do is start the engine and let it warm up for a few minutes, so you get oil in the lifters. Then remove the valve covers and do this adjustment.

1. Turn engine over to TDC for compression on #1 Cylinder (timing mark on balancer should be lined up with the Zero mark). You can also tell by the valves on number 1 cylinder should be closed.

2. Adjust the following valves: the exhaust valves on cylinders 1, 3, 4 and 8, then the intake valves on cylinders 1, 2, 5 and 7. Adjust them by loosening the pivot nut in the center of the rocker arm until you can rotate the push rod between your fingers. Continue to rotate the push rod while you tighten down the nut. As soon as pressure stops the push rod from turning, tighten the nut an additional complete turn.

3. Rotate the engine clockwise one complete turn and line up the groove with the timing mark. Both valves on the number six cylinder should now be closed. Adjust the following valves: The exhaust valves on cylinders 2, 5, 6 and 7, then the intake valves on cylinders 3, 4, 6 and 8. Adjust these the same way as mentioned above.

That's the info on the adjustment if you need to do the valve/rocker arm adjustment.

[scoutcamper]

An update(sorry if it seems like i am rambling, just want to put down all the facts): I believe the oil pressure is related to the clattering. Yesterday at an autocross i wanted to show a friend the clattering, and the engine was cool at the time. No matter what i did it would not clatter. The oil pressure was high at the time because the engine was cold. The oil pressure was low by the time i got home and it clattered just fine. Also: On the freeway(in excess of 65 mph) when you first step on the gas after you have let off you can hear clattering that stops when you accelerate.

Also: I have hydraulic lifters in this engine so i am told the rocker alignment procedure might be different?

[GMCJOE]

Hydraulic or hydraulic roller lifters? All lifters are hydraulic. Flat tappet and hydraulic roller lifters are adjusted the same for pre-load . I am not sure on Roller Rocker Arms, if the adjustment is any different. Haven't installed any yet. Regular rocker arms are adjusted as I described before.

Still sounds to me that you have an oil pressure issue after it warms up. Excessive bearing wear, or bad oil pump. Doesn't sound to me that the oil is making it up to the rocker arms thru the push rod. The lifters are responsible for pushing the oil thru the push rods.

[scoutcamper]

New Symptom: Engine smokes on startup like it needs valve job. If i get a valve job that should fix all my issues, correct? Any guesses on how much a valve job should cost on a SBC 350?

[GMCJOE]

A valve job will not fix all your issues. And the smoking may not be related to the valves. There is a lot of factors to consider before jumping to that conclusion, but it is plausible since you probably haven't been getting enough oil to the heads to lubricate the valve train.

Honestly, in my opinion, I believe you should pull this motor out of the truck and rebuild it. Give it a new set of main bearings, replace the cam bearings, and put a new oil pump in. Check piston wear to see if you need to bore it, or just put new set of rings in. With the head, I would just say get the valves ground and new valve guides/seals.

[GRX]

Originally Posted by geezer#99

Before you pull the covers take a 3 foot long piece of old broom handle. Put one end behind your ear and put the other end on various spots on your motor. You'd be amazed how easy it is to narrow down the source of a noise.

broom handle, axe handle etc ... Agreed, that trick works very well. A red neck stethoscope of sorts. Think you'll find you have valve train problems. Hopefully the rockers haven't cut into the side of the press-in rocker studs. Replacing them can be a big job. And SBC don't run forever. That's the inline 6's.