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#1449483 Tue Apr 26 2022 01:08 PM
Joined: Sep 2013
Posts: 1,416
M
'Bolter
The 1951 truck's 57k mile original 216 in my tagline is quiet. I run the valves at the Chevrolet min. clearance since it's not a real work truck the majority of the time and the just switched to summer 20w50 oil cushions the vast majority of normal sounds. Of late, as in the last 200 miles I've been hearing a low frequency very slight sound. Last evening after driving the four mile round trip to feed the horses I slowed the idle down to around 450 rpm, and did the following:

Pulled plug wires to try and isolate the sound to a cylinder. No change from pulling wires.

Used an old shovel handle as a stethoscope, the noise is in the front half of the engine. With the wood handle to ear, you can easily pick out the lower frequency noise from the tappets.

And then the new noise went away.

At this point I see one of two options, pull the pan and check main and rod clearances, last time I checked with Plastigauge about 15,000 miles ago everything was within specs.

Or, just let it go for a bit and see if it gets a little more noticeable, at the moment I'm likely the only one that would notice it.

One last question, anyone ever had a fuel pump make a noticeable knocking sound? I've had engines you could hear the mechanical pump working at idle, I'm thinking that "could" be what's going on. Of course why did it just start out the blue.

Thanks for any thoughts.

RonR


1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



Joined: Apr 2005
Posts: 10,782
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
Ticking sounds are almost always valve train related while knocking is lower down. Can’t recall a fuel pump making noise.


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2) “Emily”
‘39 Dodge Businessmans Coupe “Clarence”



"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)

Joined: Jul 2014
Posts: 342
1
'Bolter
I have encountered knocking fuel pumps. When the rocker-arm pivot pin gets loose they will knock, aside from leaking oil.

Twenty/fifty motor oil is a heck of a lot thicker as you pour it out of the bottle than is 20/20w. If you're not working the engine hard I would stick with the factory-recommended 20/20w, if you can find it; straight 20 is probably fine. You don't say where you are but unless it gets very hot I'd stick with SAE20. These old engines ran rather tight clearance on rods and mains and quite low oil pressure (15psi) hot and running. That's not enough to push much oil through if it's thick oil.

You say clearances were fine 15,000 miles ago and unless you've abused the engine in some way I wouldn't think it would have changed since then. I would just run it and see if the noise returns or gets worse.


51 3800 PU, 55 235 (w/cam, headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
Joined: Feb 2004
Posts: 24,540
H
Kettle Custodian (pot stirrer)
Rod knocks have a tendency to create a double-tap noise when a spark plug is disabled. Main bearings are more likely to cause a lower frequency "thump" type knock that doesn't change with or without spark. A main bearing knock will also make a "thump- thump- -thump" noise during acceleration that goes away or diminishes noticeably once a steady speed is achieved. I've seen several engines get an "in the frame" rebuild over a noisy fuel pump. A broomstick, dowel rod, or a long screwdriver held against the pump housing at idle will usually pinpoint the noise pretty reliably. Try removing the fuel pump, blocking off the hole in the block, and running the engine on a gravity fed fuel tank.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

WAG MORE- - - - - -BARK LESS!
Joined: Sep 2013
Posts: 1,416
M
'Bolter
A clue. The rogue sound is at half the engine rpm. I counted and got 44 in 10 seconds, or 264 in a minute. I didn't have a tach hooked up but that's going to be half speed. So, if my logic is sound and a cylinder fires once ever two revolutions, it's likely piston, or rod (big or little end) related. That said, I'm still surprised I didn't detect a change by pulling plug wires.

RonR


1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



Joined: Feb 2004
Posts: 24,540
H
Kettle Custodian (pot stirrer)
A fuel pump also operates at half crankshaft speed, since a lobe on the cam actuates it and camshafts turn at half speed.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

WAG MORE- - - - - -BARK LESS!
Joined: Sep 2013
Posts: 1,416
M
'Bolter
I used 3 different listening devices (1" dia. oak stick, 3' long 1/2" extension and short length of water hose, wood is best) to try and get a better handle on an exact location in the block. Not much luck, but I did pretty much rule out the fuel pump. Now that said, it's an easy thing to pull the pump and put a plate over the hole to do a real test. May very well add that to the list.

One odd observation I mentioned in the original post, after a bit at low rpm the knock goes away. Happened again today, however bring the rpm up to 1500 or so and it's back, let it idle for 10 minutes or so at low rpm and it goes away.

RonR


1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



Joined: Mar 2019
Posts: 1,379
G
'Bolter
Just a thought, did ya look for an exhaust manifold leak? Couldn't change the noise killing cylinders via spark plug wires, and seems repetitive. Not to mention, comes and goes?..

Joined: Feb 2004
Posts: 24,540
H
Kettle Custodian (pot stirrer)
Originally Posted by moparguy
One odd observation I mentioned in the original post, after a bit at low rpm the knock goes away. Happened again today, however bring the rpm up to 1500 or so and it's back, let it idle for 10 minutes or so at low rpm and it goes away.

You've probably got a misaligned oil spray tube that's starving a rod for oil at speeds above idle. I have an aiming fixture that's used with a water hose or a solvent tank pump to bend the nozzles for a correct squirt into the rod dippers at running speed.
Jerry


"Freedom's just another word for nothing left to lose"
Kris Kristofferson

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

WAG MORE- - - - - -BARK LESS!
Joined: Sep 2013
Posts: 1,416
M
'Bolter
Thanks all for the help. The Plan. I'm going to (in the next few days) pull the pan and use water to see if all the sprayers are spraying the same. I don't have a way to do a proper spray tube alignment adjustment, but perhaps I'll spot an anomaly if there's one spot. Then drop caps looking for obvious signs of distress. I'll also be breaking out some green plastagauge.

If an obvious issue isn't found and that includes the wiggle, push/pull rod test on the wristpins......we'll see what happens next.

I do have a purchased as good, 1959 261 that's cast in the 1954 mold setting in the shop. Before I do a serious amount of work on the 216, or actually anything beyond pulling the pan I'll go as far as necessary into the 261 to make sure it's ready to put back in service. Been needing a good excuse to put in on the engine stand and get it in the truck. Just didn't want to do it right now. Other projects on the top of the list need serious attention. Guess it's good to have a job though.

RonR


1951 3600 with Clark flatbed, T5, 4.10 rear
1970 340 Duster
1990 5.0 V8 Miata (1990 Mustang Gt Drivetrain)
1951 Farmall Super A



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