Valve train noise

[Marty68]

I have a 51 GMC. it has a 1964 283 believed to be un rebuilt. But decent shape. It has (if the guage is right) about 45psi oil pressure going down the road. It develops NASTY valve train clatter seems one cylinder. When it is a half quart low..
Ease post your opinions experiences.

[vince1]

Maybe start with a compression check? See if the valves are loose at all in their guides? Do those valves on that cylinder open as far as the others? If it doesn't leak oil yet necessitating an overhaul, maybe you could get by with just changing a couple of lifters?

If it were me though I would suspect it needs; rings, bearings, seals, cam, chain, lifters and possibly a head job. A great backyard overhaul project. Others may suggest a professional overhaul or a new engine as it could be less expensive than the overhaul.

[jayoldschool]

On my 65 C10, I had a rocker nut that kept backing off. Tighten, lash properly, a few days of driving it would back off. Fixed with new nut.

However, if it only happens when the oil is getting low, it must be an oil delivery problem. Once you have the valve cover off, start with checking the lash correctly. Inspect for broken springs, too. If all ok, run the engine with the cover off. It won't be messy unless you rev it. Watch for oil coming out the top of the pushrods/rockers. Figure out which cylinder, and troubleshoot from there.

[AussieinNC]

Can almost guarantee the pickup screen on the oil pump has fallen out of the oil pump....adding more oil brings the sump oil level up over the inlet hole and oil pressure comes good again.

One cylinder noisy could also be a bad lifter leaking down and opening up the vale lash setting...this is what you hear as noise...

When its noisy, remove the valve cover where the noise is coming from and check the valve lash on each valve....just turn the nut in middle of each rocker down 1/4 turn while engine running...the noisy one will quiet down immediately.

45 going down the road on a dash gauge seems low...can you check the oil pressure with a different gauge?

Let us know how you go...

[Marty68]

I have no idea of the history of this engine it has rear main leak. I have changed oil twice. I have owned it for a year and likely 3500 to 4000 miles. Here is a picture of heads. Seems very clean to be 55 years old.

[Marty68]

it has only made this noise on 3 occasions. next time it does it I will gently get it home and tweak rocker nut. I have never rebuilt an engine. I do like the thought and look of the old school 283. date code is august 64. hard to say if it has been apart I had fuel pump rod out last weekend it looked worn on cam but not worn out. seemingly clean inside.

[AussieinNC]

The block is a 283, early series with rear block breather...road tube style block.

The heads look like common 3737775 castings...see if you can find a casting number on the head surface....also post a pic of the front end of the head....

You said you have changed the oil twice...did you use a synthetic detergent oil ?

If you used a late model synthetic oil, did you add ZDDP (zinc additive) to the oil as flat tappet cams need this protection....

The cleanliness of the engine in general points to it being overhauled and or repaired sometime in its past....

Did you identify the cylinder that was causing the rattling noise?

[vince1]

If that is the case that the pick up screen fell out of its oil pump socket you could check for that possibly by looking through the oil drain plug hole. Borescopes are becoming cheaper everyday too so that you could get a real good look. Or rent one.

[burnin oil]

being the noise is intermittent i would call this a candidate for Murphys mystery oil. Probably a lifter starting to go bad. 45 psi of oil pressure is fine hot. The old thumb rule was 10lbs of oil pressure per 1k rpm for race motors. My built motor runs 45 also.

[Marty68]

Originally Posted by burnin oil

being the noise is intermittent i would call this a candidate for Murphys mystery oil. Probably a lifter starting to go bad. 45 psi of oil pressure is fine hot. The old thumb rule was 10lbs of oil pressure per 1k rpm for race motors. My built motor runs 45 also.

this is my thought.

no I have not determined which cylinder. it IS on the passenger side 2 4 0r 6

engine casting # is 3849852
bellhousing # is 6263756
old intake 3840905
head cast date h 294 =aug 29 64 so 65 model year

my GUESS, because large hole in bellhousing, and rams horn. (passenger side, driver side changed to create room for old steering) is this came from a 65 truck. I could be way wrong.

[sweetk30]

worked on a 283 one time with aftermarket chrome dip stick . had lifter tapping like crazy . noticed oil was nasty so i did a oil change and filter . just to check things i drained the oil in a clean tub and found just over 2qt was all that was in it and the canister filter body drained also and the dip stick said FULL

i finished the job and added 4 qt of oil and fired it up and she was SO MUCH BETTER sounding . i then marked the dip stick for 4qt low and added a 5th qt and marked it for high . i then cut off almost 3 " of length of the dip stick tip .

not saying this is your problem but could be .

[AcampoDave]

I know it seems obvious, but could it be something else? Like an exhaust leak, or even a plug wire jumping spark. The plug wire thing happened to me once and I thought it was a slight tappet noise. Even checked my valve lash and all that stuff before my buddy caught the spark jump which suprised me because I thought it ran fine.

[gvw5400]

I know it seems obvious, but could it be something else? Like an exhaust leak, or even a plug wire jumping spark. The plug wire thing happened to me once and I thought it was a slight tappet noise. Even checked my valve lash and all that stuff before my buddy caught the spark jump which suprised me because I thought it ran fine. I had this happen to me on my dad's 77 K-10, he was complaining about a sticking lifter. I drove it home and you could hear it click. but in the shop I found a bad plug wire that would occasionally fire a 3" spark from the boot on the cap
to the firewall. Big cap HEI can really crank out the voltage !! I am sure the module life
has hammered by doing this.
Hope you find the problem! All the Best, Dirk

[Marty68]

[QUOTE=gvw5400;8748777]I know it seems obvious, but could it be something else? Like an exhaust leak, or even a plug wire jumping spark. The plug wire thing happened to me once and I thought it was a slight tappet noise. Even checked my valve lash and all that stuff before my buddy caught the spark jump which suprised me because I thought it ran fine. I had this happen to me on my dad's 77 K-10, he was complaining about a sticking lifter. I drove it home and you could hear it click. but in the shop I found a bad plug wire that would occasionally fire a 3" spark from the boot on the cap
to the firewall. Big cap HEI can really crank out the voltage !! I am sure the module life
has hammered by doing this.
Hope you find the problem! All the Best, Dirk[/QUOTE

it is definitely not a tick or a misfire.

[gvw5400]

Any luck on the diagnoses ?

all the best,

Dirk

[Marty68]

runs great and quiet as a mouse unless low on oil.

[toolboxchev]

First of all oil is not oil. There are hundreds of brands out there.

You could have a lifter collapsing. It is leaking down when the engine, and oil gets warm. You have a pretty significant issue, In my mind, If it were mine, I would immediately also look into what Leon is saying also.

As far as motor oil, this stuff:https://www.valvoline.com/our-produc...vr1-racing-oil

It is specifically designed for our flat tappet motors.

I have close to 100K on a top end rebuild that was not supposed to work due to the lower end needing help also.

I am starting to become their trumpet in the industry, not paid!

Take a paint pen and mark a line on each one of the pushrods near the rocker arm when you get done doing what your doing. When running each push rod should spin in relationship to their hydraulic lifter. It is how these motors work. Make sure they are all spinning, some will spin differently to their 15 other brothers.