Crankshaft and Journal question

[brimis]

My 84 L83 started to "knock" about two weeks ago. Upon getting the car home I noticed the damper had split. Hoping this was the problem I removed the belt and damper and started the car only to here the same "knock". I should mention as I increase throttle the "knock" becomes faster and not louder. Oil pressure is fine, steady at 47 or so while parked in the driveway. I pulled the vavle covers and the pushrods and rocker arms appear to be fine, meaning the pushrods are moving and the rocker arms are moving freely, not to mention the "knock" did not get louder after removing the covers. I dropped the oil pan to check the connecting rods, caps, mains and journals. The mains appear to be fine. My questoin is how much if any should the connecting rods/caps move.
I can grab the caps, 1/2, 3/4, 5/6 and 7/8 and move them ever so slightly left to right, but not up and down. How much "play" should there be on each journal?

 

[WhalePirot]

I would listen for the knock while BRIEFLY running the engine with the serpentine belt off. The knock might not be internal.

 

[G Winter]

If your talking about end play, front to rear, then there would be just enough that you could feel it. Might want to check a manual for specs on
the end play. What type of knock is it? hard knock , light knock, single or a double knock? Maybe a broken piston ? Is this by chance an auto. sometimes the flex plate will break. usually a light sounding knock .

 

[Ken]

...ever so slightly

Is that like "just a tad"? :L

The rod bearing clearance should be .0013-.0035" from the factory, with service recommended at .0035" max, and a rod side clearance of .006-.014".

 

[G Winter]

Wow, Ken , .0035 seems lose to me. I think in the old days it was more like .0025 btw how you make that quote thing work ?

 

[Ken]

.0035 is straight from the 1987 L-98 service manual. The 1990 L-98 was the same animal.

Man, I hate it when I have to get back up from my chair, retrieve the book and look it up again, just to allay my fears that I mis-typed, transposed, or perhaps mis-read the numbers. I am so full of self-doubt.

 

[G Winter]

:L I wasn't doubting what you posted , just alluding to the fact that they are building that part of the engine loser. Maybe for gasmilage ?

I will be more carefull on how I state things in the future, don't want you getting out of your chair for no reason.

 

[motorman]

My 84 L83 started to "knock" about two weeks ago. Upon getting the car home I noticed the damper had split. Hoping this was the problem I removed the belt and damper and started the car only to here the same "knock". I should mention as I increase throttle the "knock" becomes faster and not louder. Oil pressure is fine, steady at 47 or so while parked in the driveway. I pulled the vavle covers and the pushrods and rocker arms appear to be fine, meaning the pushrods are moving and the rocker arms are moving freely, not to mention the "knock" did not get louder after removing the covers. I dropped the oil pan to check the connecting rods, caps, mains and journals. The mains appear to be fine. My questoin is how much if any should the connecting rods/caps move.
I can grab the caps, 1/2, 3/4, 5/6 and 7/8 and move them ever so slightly left to right, but not up and down. How much "play" should there be on each journal?

the split damper is a sign that the crank "MAY" be cracked. you also could have something on top of a piston. check your plugs for any sign of something hitting them. the side to side movement on a pair of rod should be .015 to.020

 

[SSTibet]

Same here...

Man, I hate it when I have to get back up from my chair, retrieve the book and look it up again, just to allay my fears that I mis-typed, transposed, or perhaps mis-read the numbers. I am so full of self-doubt.

Ken, do not hate this habit of yours; same personality here... I review my messages at least a few times before posting them and still edit the post once or twice... I have accepted the fact that this is my personality trait, and I think I like perfection. Perfection brings some stress but a lot of quality to the way we live. Our types plan to the finest detail before execution and likes avoiding surprising outcomes.

And I am not going to give up my habits, they are what makes me who I am.

Cheers buddy,

Selim

 

[brimis]

I did check for noise with the belt off and it is present. I pulled the plugs and they are white, very clean.

 

[tnovot]

I think it would be a good idea to get a stethescope (or piece of rubber hose/tubing) to listen while the engine is running in order to more precisely locate the noise. Whale made a good point, the noise may not be internal.
Is the oil pan still off? If so, maybe a good idea to pull the rod caps and visually inspect the bearing inserts. When you drained the oil, was there evidence of small metallic flakes in the oil or in the bottom of the pan?

 

[jmccloud]

My sister-in-law once had a Nova small block (automatic trans) that developed a knock. Turned out to be a crack in the splice plate (the plate that connects the crank to the torque converter). Took us days and a stethescope (actually a piece of garden hose stuck in one ear) to locate the source.
Sounded a lot like what you describe.

 

[Rufus1050]

I'm with jmccloud on this one...if you did the belt thing and the cap checks, go for the flywheel. Several weeks ago, I bought a ford pickup that had a bad knock in it that drove me crazy for a day or two. My son seemed to think that the noise was comming from the tranny and we checked it. Now this was an automatic and we were able to pull the inspection plate...when I put the wrench on the first nut I was surprised that I could move the flywheel without loosening the nuts. Turns out that the flywheel was cracked and this was my problem. I later learned that those Ford 300's are bad about that. Give that a try...just might be your problem.

 

[vette-dude]

I'm with jmccloud on this one...if you did the belt thing and the cap checks, go for the flywheel. Several weeks ago, I bought a ford pickup that had a bad knock in it that drove me crazy for a day or two. My son seemed to think that the noise was comming from the tranny and we checked it. Now this was an automatic and we were able to pull the inspection plate...when I put the wrench on the first nut I was surprised that I could move the flywheel without loosening the nuts. Turns out that the flywheel was cracked and this was my problem. I later learned that those Ford 300's are bad about that. Give that a try...just might be your problem.

That would be my guess too!!!!!!!!!!! Cracked Flexplate (flywheel) or loose crank to flexpalte bolts. (That is if it is an automatic trans.)

Randy

 

[jmccloud]

If it's a manual transmission, a worn pilot bearing can give some bad noises, often when the clutch is disengaged. Sounds just like a loose rod bearing.

 

[G Winter]

Something I had forgotten about. I have seen the converter to flexplate bolts work lose also.

 

[brimis]

The oil pan is still off the car. Inside I did see small pieces of plastic, but believe it to be from the oil pump. There is no sign of metal shavings in the oil, looked clean.
I will check the flexplate and splice plate over the weekend. I did try the hose to ear, but still had a tough time locating the noise.
After the flexplate and splice plate I will remove the caps and check the cap bearings. Thanks for all the help, I'll keep you posted.

 

[jmccloud]

Noise source

One of my kids replaced his oil pan gasket years ago and afterwards got a severe knock. Turned out that he'd jacked the engine up with a board across the lowest part of the oil pan and dented the center of the pan ever so slightly. The oil pump was rattling against the pan and making an awful thump. We took the pan off and pushed it back out (less than 1/8") and the knock was gone.
Take a close look at the pan's shape.

 

[G Winter]

The oil pan is still off the car. Inside I did see small pieces of plastic, but believe it to be from the oil pump. There is no sign of metal shavings in the oil, looked clean.
I will check the flexplate and splice plate over the weekend. I did try the hose to ear, but still had a tough time locating the noise.
After the flexplate and splice plate I will remove the caps and check the cap bearings. Thanks for all the help, I'll keep you posted.

Plastic in the oil pan? now or at sometime the timing gear may have failed , if they didn't use the plastic coated timing gears in the vettes then someone please jump in a correct me. If the plastic broke on the cam gear it is possible that the knock is the chain on the gear. Thoughts from someone else on this ?

 

[brimis]

Scav, you've given me hope. I've heard the cam gear may be plastic. I will pull the waterpump and timng cover and cross my fingers. I'll keep you posted.