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Heavy Tapping low in the Engine

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RAC68

RAC68

Darth Vader
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Hi All,

A friend has just learned that the knocking within his '67 BJ8 P2 engine could be caused by a warn connecting rod bearing. This is an area I have little experience and would like suggestions on how to identify the faulty connecting rod bearing (if that is what it turns out to be) and how to correct the issue without removing the engine and/or entering into a full engine rebuilding.

To locate the knocking/ticking noise, a stethoscope was placed along the valve cover showing no good indication that the noise was emanating from the Valve Train. However, a stronger indication seem to indicate that the sound was emanating from the lower end of the engine block in the area of the cam or crank shaft. So, what could create a knocking noise in a regular rhythm within that space?

Locally, the consensus of a few Healey-owner friends suggests that since the engine pulls strongly with good oil pressure increasing with RPMs, the knock is not emanating from a main bearing but could be coming from a single cylinder. Although it was hoped that the knock would disappear when the problem cylinder spark plug was disconnected, this did not happen and the knock continued through the deactivation of all cylinders, one-by-one.

So, what could cause this knocking noise and how should it be addressed for identification and resolution? Your suggestions would be appreciated.

Ray(64BJ8P1)
 
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HI Ray:

Sometimes pulling the spark plug wires one at a time can locate a rod knock in the engine
, if so the knock will disappear when the correct cylinder wire is puled.

What ever the cause it must be located and corrected.
 
Hi Keoke,

Thank you for your response. We performed that test and found no obvious difference as the knocking continued after pulling each spark plug wire with no change in sound volume or rhythm. Is there an additional test that would identify the location of the knocking noise?

Thanks again,
Ray(64BJ8P1)
 
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sticking lifter? pulling the valve cover and spinning the engine by hand might show you something.

if it is in the lower end of the engine for sure, i think i would pull the oil pan. take a look at the bottom end. something loose hitting the crank or laying in the pan? also you can see the cam from there as well. check rod bolts, nuts, etc.
 
My noise was a broken piston ring with pieces smashed into the top of the piston. The noise was heard at #1 cylinder, but it was #6 that was bad.
 
It's probably not your issue but make sure there is not interference between the oil pan and the crankshaft.

Some years ago I was driving my now-ex wife's BN7 and ran over some small object which bounced into the oil pan. Immediately I heard a tapping sound that varied directly with engine RPM's. I drove home, jacked up the car and saw that the front left corner of the pan was pushed in about 1/2" and when I started the engine I could feel the interference from the front-most crank web and the pan. It was easy to pound out the dent, backing up the pan with a sandbag, and the noise disappeared.
 
Thanks All,

I had originally suspected a valve train issue but others have indicated the problem was more in line with a warn connecting rod bearing. Since this has only been suggested as being a much more dramatic issue then a valve train issue, we have not pulled anything as yet. However, when pulling the pan, other then an obvious loose or broken part laying in the pan, how would we identify a warn connecting rod bearing? I am assuming one as the sound seems to be a singular regular tapping.

We performed the test to identify the cylinder with the warn connecting rod bearing as our friends and Keoke suggested (pulling each spark plug wire and listen for the diminished knock) but the knock never seemed to diminish in volume or regularity. Although we will perform this test prior to dropping the pan, if the results are the same, what should we look for at the connecting rod journals that would validate that this is our problem?

I was thinking that, if the above test rerun showed no noticeable change in results, prior to dropping the pan it seems good logic to pursue Drone Dog's suggestion of the possibility that it is a valve train/lifter issue. This would be facilitated by removal of the valve cover and observation of the valve train followed by the removal of the side covers to pull and examine the lifters. A compression had been performed prior and compression was normal in all cylinders. Any suggestions/thoughts as to tests or observations in this area?

Thank you All for your responses,
Ray(64BJ8P1)
 
I suggest dropping the pan (easy to do) and plastigage all rod bearings - then you will know if they are within tolerance and you will also have a chance for a visual examination of the bearing shells and crankshaft to look for scoring/galling etc.
Dave
 
Hi Dave,

Yes, that makes good sense and will follow your suggestion. For some reason, I can't seem to find the torque specs for the connecting rod end cap bolts in my manual. Could you give me direction on where to look for this specification?

Thanks again and all the best,
Ray(64BJ8P1)
 
When you drop the pan and remove the big end caps, paint mark the parts for orientation and remove the caps one at a time. Put the parts back together as you exclude them from being the culprit.

Pick the bearing shells out of the rods and caps. If the engine has been running fine before, bearing damage is likely to be visually noticeable. Look for worn through spots, smeared material, and score lines. When/if you find any, take a very good, critical look at the crank journal. If the crank journals shows signs of damage, stop your detective work and plan to remove the engine to address the crank.

Though the noise may seem to be coming from the big ends, be prepared to examine the main bearings if you don't find big end bearing damage.
 
Hi all,

Does 50 ft Lbs sound correct for the torque setting of the big end cap bolts on the connecting rods?

Ray(64BJ8P1)
 
Hi Steve,

I can't imagine a screw on the connecting rod that would be beefy enough to take 50Lbs of torque. I agree, it must be for the connecting rod bolt.

Thanks,
Ray(64BJ8P1)
 
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A set screw in Brit talk is generally a bolt that is threaded all the way to the head and clamps two components without using a nut.

I have seen set screw in US speak used to describe what is usually called a grub screw in UK. Just different terminology.

Danny
 
I suggest the time you are going to spend removing and checking items with the engine in situ is a waste. Ultimately if you find something wrong you will end up removing the engine anyway, there should not be any knocking from a normally operating engine, remove the engine and inspect it properly then rebuild as required it will save you time and money in the long run.
 
Dandare said:
A set screw in Brit talk is generally a bolt that is threaded all the way to the head and clamps two components without using a nut.

I have seen set screw in US speak used to describe what is usually called a grub screw in UK. Just different terminology.

Danny
Click to expand...

Danny - Thank you for clarifying this. I guess here it's referring to a bolt that clamps two components together. There's no other screw on the later connecting rods.
 
Low end thunk is not good. If it's a rod bearing, chances are very good the crank throw is also bad (now).

Mains, rods, interference, loose flywheel, all sort of things.

Pull the engine, take measurements as you tear it down, inspect, if pistons and bore are good, hone and new rings anyway.

Seen to many half-arsed jobs that you end up doing again. (why is there never enough time to do the job right the first time, but always enough time to do it again?)
 
Well TOC:

On this side of the pond you don't just run out to the detach N pull the engine.
 
Really? Well, you can jack it up, drop the sump, play around understanding torques and plastigage readings......and still not find it.

Buy new bearings, figure it must be the pickup tube hitting the crank and order one of those.....and somebody had an issue once with a muffler bearing...so replace the exhaust....and still end up yanking the motor after you spent a pile of money and a load of time.

Of course, it could be the coil.....it's ALWAYS the coil, right?


Collapsed skirt. Broken rings. Cracked piston, Wrist pin (gudgeon pin) come adrift. Broken crank (had one of those once), flywheel loose, broken pressure plate whacking the inside of the bell housing...loose front damper/pulley, water pump bearing, timing chain slap.....keep after it, it will be easy to pull because all that will be left is the bare block and crankshaft.

Having the engine out and on a stand in good light is a WHOLE lot better than underneath with a torch.

I had to yank the engine/trans on my MK2 Jag...in a garage with a six foot six top header....and no hoist or pit...and that was fun, but necessary.
 
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