The Stovebolt Site Forums The Shop Area Engine Shop just rebuilt - now an engine knock

This is better drama than my wife's daytime soaps.
I'll bet that knock is the PO having sex in the bed (of the truck).

And you thought the drama was over already ?...OK, been out of town a week or so, but here's what I know...
Pulled the pan, removed that %$&#@ makeshift re-threaded bolt, nut and lock washer that was holding bearing cap on - which by the way, was very snug. Checked rod bearing clearances on two random rods....checked out to about 0.02 to 0.025, which I believe is acceptable. Checked and retorqued all rod caps and main bearing caps. Did not pull main caps to check clearance since the noise is not characteristic of a main bearing knock. Oil pan looks clean. No scoured bearings, crank OK. Put pan back on. Yesterday, I pulled the side cover to check lifter/rod area. No. 1 intake (or exhaust...can't remember which) solid lifter is broken - literally the top part has seperated from the main body of the lifter....clearance too much also. Pullled valve cover, pulled push rod and replaced old broken lifter with new lifter....Fellows, could this be the "knock" I was hearing ???? I sure wouldn't think that little hollow lifter could make such a deep thumping sound like I've been hearing.....Will put distributor back in (other problems over the weekend with this thing) and start her up today to see what she sounds like.

I'm sure that 0.02 to 0.025 rod clearance would be a noise problem. I'm sure that you mean't .002 to .0025.

I thought the noise was from the #4?

If one of your rods is bent, that could create some noise too.

dublenaught,

Things are looking up. You were searching for something wrong and you found something wrong. The odds are in your favor that this is the problem. Thanks for the update.

Stuart

I will bet its quiet when you get her running again. Check the other lifters, if ones bad, you could have more. Reset all the valve clearances while you are at it. Joe

The SAGA continues....the bad lifter apparantly wasn't the problem. the noise is still there...again, on acceleration, again, seemingly "deep" in the bottom of the engine. Just to re-cap, the engine shows great oil pressure at all times. I've pulled the pan and rod bearings are tight. NO broken lifters now....this isn't valve clearances either. It's not the fuel pump. It's not the water pump. I've checked everything....THIS IS KILLING ME.... It is only noticable when warmed up, and only does it on acceleration, guys. Very dull...thud, thud, thud sound. MY MAIN BEARINGS CHECKED OUT WHEN INSTALLED. Should I pull the darn pan again and re-check those??? The only logical thing left, accordiing to other posts I"ve read, is that the harmonic balancer is loose and/or making the noise. How can I check it out? Any more ideas???

What type of driveline does the truck have?

What does the oil pressure do with hot oil?
what weight of oil are you using?

Does it "knock" in each gear when accelerating?

Is the exhaust pipe close to anything?

If you lug the engine at low speed in high gear,des it really Knock hard?

Is the fan belt really tight?
try it really loose, what happens?

Had you driven the truck a lot before the rebuild?

Sorry if these have been asked already, I am just throughing them out. Its really hard to fix from a computor screen, I wish I was closer so I could hear it in person! Joe

Have you checked the flywheel bolts for the proper torque? Your symptoms sound like a classic main bearing knock. I drove a 1960 Rambler American flathead 6 from Central California to Nashville, TN. with a similar knock, and discovered the main bearings had about .002" too much clearance, after an in-frame rebuild before the trip started. That one also wore out a new set of piston rings in 2500 miles due to inadequate cleanup of the cylinder walls after a honing job. The last couple of fillups on that trip, I had to stop midway and add oil. It was using 3 quarts of oil to a tank of gas!
Jerry

I don't know if this is a possibility with your engine, but it came to mind. Maybe some of the others can tell you if this is possible with your engine or not.

Years ago, the mechanic in the stall next to me had a noisy situation after a top end overhaul. Not the same type of engine but I suppose it could happen...

He used the head gasket from a smaller motor with the same head bolt pattern. The piston was slapping the steel ring of the gasket that was smaller than the cylinder. Made a noise we were unfamiliar with and we checked a lot of things before tearing the head off and finding out the answer.

a deep dull thud sure sounds like a bad main to me. Builder, did he use a 305 gasket on a 350?-saw a guy do that once, only I saw it after the fire burned thru the gasket after some miles-had the "fire ring" from the gasket neatly on top of the piston like an extra ring.

I would be guessing a main bearing myself too. Sometimes when installing them, they don't snap in to place in the block right away and they can appear to be tight. Then after torquing and releasing the clearance changes. I would be tempted to use the plasigauge again and check them one by one.

I have been recently told by my mechanic that this is a bad wrist pin on No. 1 cylinder. I know what I said earlier. My diagnosis, I suppose was wrong. Let's re-cap.....plastiguage checks out tight with both 6 rod bearings and all 4 mains. With two of us working together this past saturday, he pulled plug wires with new plugs, and the noise went away upon pulling No. 1. Knock is just on acceleration. No other time. No noise when no. 1 plug wire is pulled. If this is a wrist pin, then I suppose "all I have to do"...is pull the head, pull botom pan, pull piston, and replace eithet the pin or the entire piston assembly. Any thoughts ???

A loose wristpin can usually be heard at idle. If the wristpin is loose on the rod, I wouldn't want to run the motor any more.

yes it is nice to be able to replace with out pulling motor i hope he was right

The wrist pin on that engine is clamped tight by the split end of the connecting rod with the clamp bolt in it. If there's actually a wrist pin knock, its caused by the pin being loose in the piston, not the rod. Replace the piston/pin assembly.

Another possibility is the piston being loose in the cylinder, creating a "piston slap". That's usually a much lighter-sounding noise, though, a ticking type of noise as the load comes off the piston after acceleration, not during. If you've got cast iron pistons, there used to be a spring steel expander available from Perfect Circle that was placed between the wrist pin boss and the piston skirt with a special set of installation pliers. I haven't seen a set of them in close to 40 years.
Jerry


Jerry

I wonder if the problem is a bent rod?

I chased an oddball knock on an Olds 350 through three teardowns. It turned out to be a twisted rod that was letting the piston do some strange things halfway up the stroke.
Jerry

No matter what. DON'T GIVE UP!! You'll get it figured out.
DJ