TR2/3/3A Noise seemingly from Distributor drive gear

[LBCpoor]

Turning to the Jedi for thoughts..... I have a recently rebuilt engine, all new...89mm pistons/jugs, main & rod bearings, wrist pins, oil pump innards, distributor pedestal bushing, crank turned 10 under, 270 cam w new cam bearings, new timing chain and sprockets, push rods, tappets and rebuilt rocker assembly (not rollers).. if I could find it I replaced it. I'm chasing a tapping noise that seems to be coming from the distributor/oil pump area. Steady, fast tapping that will disappear at 1500 to 2000 rpm. Distributor was mounted with end play determined using washer method in manual (yes, washer was removed after calculation)...needed a .004 paper gasket to achieve desire clearances. I've found that if I loosen the distributor pedestal and shim the pedestal .100 (yes that is a lot)on the outboard side (pushing it inboard - toward the block) the noise is all but eliminated. With the shim in place it sometimes taps (almost a rattle) for a second or two at start up and shut down....but other than that no unusual noise. Compression is good and even in all cylinders, have pulled plug wires to check for changes..none noted. Exchanged distributor..no change. Exchanged pedestal...no change. Exchanged distro drive gear...no change. Have removed fan belt...no change. Valves have been adjusted...checked and rechecked. Engine runs strong with no unusual noise under load. New cam/old drive gear....but no evidence of unusual wear on gear. Stethoscope inspection indicates sound from distro pedestal area. Definitely loudest at base. Nothing uusual noted at timing cover or high on distributor itself. Have visually inspected valve train while running with valve cover removed.....all oiling well, nothing remarkable noted. Dropped sump, inspected for interference, took a look at inners of oil pump, noting obvious
I suspect some issue with distributor drive gear/cam gear lash up or issue in oil pump or drive shaft. But I am out of ideas....turning to the Masters for your thoughts....hoping one of you may have faced a similar issue.

 

[Alfred E. Neuman]

Is the tapping at engine RPM (crank) or 1/2 engine RPM (cam)? From your description it's probably cam speed, but never hurts to check.
Maybe the oil pump drive shaft is just a fraction bent, creating a little wobble?

 

[Sarastro]

Maybe in the tachometer drive? Would be nice if it were that simple. Maybe just remove it and see what happens.

I think I'd want to eliminate a chipped gear in the camshaft or the distributor drive gear. It seems like it'd be simple to pull the pedestal and check the gear; you could then look down the hole and inspect the camshaft gear. Sorry if I worry too much about this, but it's what killed the engine in my MG TD: broke the gears, lost oil pressure, and the PO didn't notice until it was too late. (I realize that can't happen in the TR, as both the distributor and oil pump run from the same gear, but you still want to avoid it.)

 

[LBCpoor]

Thanks for the reply. Seems to be at cam speed. It’s not a deep knock. If it wasn’t for the stethoscope pinpointing the sound at the distro pedestal I would suspect timing chain noise or something interfering with it or the cam sprocket. I have purchased a new pump drive shaft and will install to eliminate that possibility. Also have new innards for the pump but don’t want to drop the sump again until I’ve exhausted other possibilities.

 

[LBCpoor]

Thanks. Have pulled the tach drive....no change. Have pulled the distro and gear more times than I can count. No unusual wear or chips on cam gear or distro drive gear. Understand worrying......trying to figure this out without causing any real damage to a fresh rebuild.

 

[bobhustead]

Do you have another dist. to try?
Bob

 

[LBCpoor]

Thanks Bob. Did that also....no change.

 

[CJD]

One very common source of knocking is the bushing for the oil pump drive shaft. A worn bushing and/or shaft will cause a knock that comes nad goes. It also wastes a lot of oil pressure at idle too.

 

[LBCpoor]

One very common source of knocking is the bushing for the oil pump drive shaft. A worn bushing and/or shaft will cause a knock that comes nad goes. It also wastes a lot of oil pressure at idle too.

Thanks for the response. I replaced the bushing thinking that it might have been worn.....no change. I will replace the drive shaft with recent purchase and see if that helps. I replaced the moving parts of the oil pump during rebuild but thinking I while troubleshooting and exchanging parts I may have tightened pedestal when drive shaft slot not engaged (at least fully) into pump shaft. May have caused some type of issue there.

 

[LBCpoor]

In the process of installing the new oil pump drive shaft. When shaft is installed into a drive gear with new woodruff key the shaft is loose in/out of gear. it will slide right out. Tried on a spare drive gear with same results. I can't find any mention of the correct condition of this assembly (loose or tight) in manual. I think some heavy grease inserted would hold it for assembly into oil pump. The drive shaft currently in the pump is tight enough that it has to be lightly tapped out of the gear. Thoughts please?

 

[sp53]

Could it be the oil pump has play?

 

[LBCpoor]

Could it be the oil pump has play?

Thanks. Possibly.....hoping to exhaust other possibilities before dropping the sump again. I have a spare pump assembly if need to go that route.

 

[LBCpoor]

So....after several months and several iterations of attempts to solve my noise issue. I finally decided to pull the nose and check timing chain and cam. Immediately found that cam gear was interfering with timing chain cover. Upon further investigation I decided to pull the cam gear to have a look at the cam. Upon removing the lock tabs I found that the cam gear to cam bolts had not been torqued allowing the cam gear to wobble ever so slightly. I learned a lesson......can’t blame the PO on this one since I was the guy who got in a hurry and evidently failed to torque those two bolts. All is now quiet on the western front! Thanks to all who responded with thoughts and suggestions!

 

[sp53]

So those little tabs keep everything together and saved the day? Without the tabs do you thing the cam gear would have come off?

 

[LBCpoor]

Yes. The locking tabs did their job! Gear come off? Most likely......yes.....but not before the noise got much worse.....or the gear cut a hole in the timing chain cover.

 

[Sarastro]

Actually, the bolts may have come loose because of the lock plates. Those things are not a good idea. The plates have to be soft enough for the tabs to be bendable, so the bolts can compress them, over time, and lose axial tension. Then, the tabs are not strong enough to keep the bolts in place very long, and they come loose. You are lucky that you found the problem before the bolts came loose completely.

I've stopped using them. Instead, I use Belleville or Nord-Lock washers, in combination with thread locker. The Nord-Locks, in particular, show a high degree of resistance to loosening in Junker tests. They can't be used for extremely high temperatures (cam gear should be OK) and the base metal cannot be too hard, as the ridges need to bite into it a bit (again, cam gear is OK).

Also, it's a good idea to read the instructions from Loctite on the use of thread lockers. Getting a good lock requires more than just dripping it on and torquing the bolt. The threads have to be clean, the locker should be applied to both M & F threads, and a primer should be used on nonferrous metals.

Google "Junker tests of fasteners" and you will find all sorts of info on this. Also, Carrol Smiths book (which I have been reading, recommended by John "CJD"), is openly contemptuous of lock plates, calling them an "idiot device."