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MG MGA - Duplex Crank Gear

I wondered why the bottom of my 1800 engine at the front was getting oily despite having the later oil seal on the timing chain cover. Have a look at the image.

Steve

Steve Gyles

Looks ok to me!

Also think it was a great idea of yours to modify the sprocket with that extra aftermarket oil drainage slot.

I suppose the principal is that as soon as the oil stops dripping, you then knew that you were out of oil! (once the smoke clears!)

Seriously though, its a really good job you found it , I shudder to imagine what damage there could have been if it had broken in use.

Have you found the broken pieces in the sump or in the the sump strainer? May be worthwhile looking inside the oil filter for them or making sure the oil passages are clear.
(Sorry if this is obvious stuff but I wouldnt be able to forgive myself if the bits cropped up in the engine later and I hadnt said anything)

Let us know how the rest of the rebuild goes, I havent rebuilt an MGA engine since 1974 so your reports are bringing back memories.
All the best
Colyn
colyn firth

Looks ok to me!

Also think it was a great idea of yours to modify the sprocket with that extra aftermarket oil drainage slot.

I suppose the principal is that as soon as the oil stops dripping, you then knew that you were out of oil! (once the smoke clears!)

Seriously though, its a really good job you found it , I shudder to imagine what damage there could have been if it had broken in use.

Have you found the broken pieces in the sump or in the the sump strainer? May be worthwhile looking inside the oil filter for them or making sure the oil passages are clear.
(Sorry if this is obvious stuff but I wouldnt be able to forgive myself if the bits cropped up in the engine later and I hadnt said anything)

Let us know how the rest of the rebuild goes, I havent rebuilt an MGA engine since 1974 so your report are bringing back memories.
All the best
Colyn
colyn firth

Colyn

Like so many people have stated in the past, this was never intended to be a rebuild, just a clean-up and repaint. However, one just removes this bit and then that bit to make inspection, clean-up and painting easier and before long the whole engine is in pieces. Only things I have not dismantled are the crank, pistons and camshaft. I should have it all back together and running in just over a week. I have ordered the new crank gear.

No sign anywhere of the broken bit. Judging by the colour, it's been broken quite a while. It's probably been held in place by the seal and fallen on my garage floor during the dismantle. The seal shows slight asymmetric wear, probably caused by the fracture.

It was certainly there last time I rebuilt it in 2001 - honest.

Steve
Steve Gyles

Might just be the picture, but the teeth on that look awfully pointy.That means the chain and cam sprocket are also less than good.

"shudder to imagine what damage there could have been if it had broken in use."

Had a very modified 997 Cooper that broke the cam sprocket - it just quit running, no damage at all.

FRM
FR Millmore

FRM is right you need both gears and a new chain
R J Brown

Steve,
glad you found the problem without real trouble.
You can never "clean up and repaint". I had a late model turbo engine with 100,000 miles on it that got a blocked oil pressure sensor. No trouble with the engine at all. I had to remove the valve cover to replace the sensor. I found .011 inches wear on the camshaft. Pulled the head for rework, found loose valve inserts. I also found scoring in the cylinders. Tore the block down, found cylinders already bored .020 inches over. New pistons, rings and everything else later, it cost me $1700.
All this just for an oil pressure sending unit.
Mike Parker

I had exactly the same thoughts as FRM, is it ok to just change the cam sprocket?
Neil McGurk

FRM/Neil

You may well be right. I do not have the history on the parts other than they were in a used engine I bought at an auction. In the first instance I will do a comparison with the new crank sprocket when it arrives next week. Donning sensibility hat it is always better to err on the safe side, so I am pretty sure it will be a new chain and cam sprocket also.

Steve
Steve Gyles

Hi Steve, Glad you found the source of the oil leak but sorry to hear it turned out more expensive than anticipated. As a matter of interest - what method did you use to remove the crankshaft nut/starter dog? cheers Cam
Cam Cunningham

Cam

A spanner!

I already had the flywheel off so I locked the crankshaft using a jemmy geometrically locked on the 2 crankshaft dowels. the nut then came undone ok.

The prices do not seem that bad. I am glad I have taken the engine down this far. Lots of small issues to sort. I also had a very small water weep out the back of the head gasket and a blocked water drain gallery. Pulling the core plugs was interesting; they just would not shift. I ended up welding bolts to them and pulling them out with a slide hammer.

Steve
Steve Gyles

That damage is typical of reinstalling a wheel on a shaft with a woodruff key where the key is not level on the shaft - it then acts as a wedge and breaks the part off that you see here in the photos.
dominic clancy

Steve - Aha - the spanner method! Locking the crankshaft with the engine out sounds good. I am ready to put on the timing cover you kindly gave me - all painted up . Will use Barney's method of spanner cushioned with a block of wood and then using the starter - hope I don't find a broken sprocket - cheers Cam
Cam Cunningham

I have totally confused myself and probably everyone else with the breakage. Of course the broken bit faces inwards. It's the pulley hub that runs in the seal. Dominic is absolutely right about about the keyway. That said, mine are absolutely straight. I have just slid the offending item on with no problems (keys are still firmly installed in channels). I can only presume that the sprocket has weakened during its life and broke during its last installation. Still no sign of the missing bit. Had the wife search the floor and up to her wrist in the engine oil that I have just drained. She is a good ferret. She found a missing rocker box bolt within a minute, whereas I had been hunting along my workshop bench for about half an hour.

I have taken sound advice and ordered a complete new set of sprockets and timing train.

Steve
Steve Gyles

Just to close this post down. I fitted new sprockets and a duplex chain. Interestingly, when I dynamically timed the engine today the pulley timing mark was absolutely stationary against the cover TDC timing mark (timing light with built in advance feature). Previously there had always been a small amount of jitter. I am glad I took note of FRM's comment that the teeth looked worn and I should replace it all. Just goes to show how worn bits can cause the engine to run off tune. I had just assumed that the chain tensioner would take care of slackness and wear in the system.

Another lesson learnt.

Steve
Steve Gyles

This thread was discussed between 21/11/2009 and 21/12/2009

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