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MG MGB GT V8 Factory Originals Technical - blurred timing marks.

Hi all,
I have had this problem since i have had the car [5 years] i have just got round to trying to fix it [had more important things to fix first], my question is what causes blurred timing marks? i have fit a new drive gear on the bottom of the distributor, i have got the timing cover off at the moment to have a look at the drive gear, this looks ok but has slight wear on one side of the gears [but not bad] can i turn this gear round? the distributor does not seem to have too much wrong with it, it is old but it's not falling to bits.

I had a new electronic ignition fitted three years ago as the one that was built into the distributor burnt out, but that made no difference to the blurring, should i just leave it as the car runs ok?
Any help/advice would be apreciated.

Thanks Graham.
gt young

You ,like me, may have a very cheap timing light. I figure if it's slow to turn off (sure sign of a cheap light) then you should look at the beginning of the blurr as the actual mark. Actually, I have found with the RV8 style extractors you can actually hear when it starts to ping and adjust accordingly. A faint but quite distinct sound as though someone was tapping a thin peice of wire or pin etc rapidly on the exhaust.
Peter

Peter,
Thankyou for your reply, i must admit that the timing light is an old one, i will have to invest in a new one and give it a try, do you know whether i can turn the drive gear round that bolts onto the camshaft? just wondered what the groove that goes round the gear was for could it be for oil supply? if so i can't turn it round.
Thanks Graham.
gt young

I'm not that expert I'm afraid.
I've heard some mention made about dialing in a new cam, but this I've never done as I've not needed to. There is a possibility that your timing chain is streached a little (if old), but I would expect that would cause your timing to jump around, not just be blurred.
Peter

With mine changing the timing chain and gears as part of a top-end overhaul made the timing rock-steady even though it didn't seem to be wobbling much. The gears and chain didn't seem to be worn on inspection but since the old ones came off the shafts much easier than the new ones went on (had to keep the two gears in line or it would jam) I assume the chain had stretched and this was enough to cause timing wobble.

Another cause of blur can be the timing light 'firing' to HT pulkses on leads other than No.1, especially if it draped over them. In my case holding the pick-up lead away from the others cures that.
Paul Hunt

Pete, Paul.
I don't think that the timing chain is at fault as it has only done 7,000 mls.[duplex with metal gears]. I have not got round to getting another timing light yet as i will have to put it all back together just to try it, i am waiting just in case anybody else has any ideas that may involve taking it all back off again [timing cover].

Good point about the timing light lead being draped over the other leads Paul, now i think about it it has been every time i have used it, i will be more carefull in future.
Thanks Graham.
gt young

Graham
The problem can be the distributor drive spindle which in some set ups is attached to the drive with a split pin -
Roger
RMW

GT, does the light steady itself as you accelerate the throttle? If so, you may have a worn timing chain or chain tensioner. Uneven cylinder pressure can cause the same situation but would also include a less-than-smooth idle.
Jeff Schlemmer

Hi Roger, sorry been away for a couple of days, the drive gear that fits onto the bottom of the distributor shaft is a new one, but that did not solve the problem, so i took the timing cover off to have a look at the drive gear that bolts onto the end of the cam shaft, this looks ok except for a slight bit of wear on one side of the gear teeth so i was wondering if it could be turned around?

Jeff, the timing chain and gears are new [7,000 mls]and there is no timing chain tentioner fitted, to be honest i have never tried revving it up to see if the timing mark steadies up, i will give that a try when i put it all back together, just wondered if there was anything i could do before i did that.

Thanks Graham.
gt young

Graham, here's another possibility: if your distributor's mechanical advance springs are already engaging at your idle speed, your timing will be erratic. That will also steady in acceleration. It won't cause any driveablity issues, just a little less performance by having to decrease total timing to compensate.
Jeff Schlemmer

Jeff, thanks for the info. would that be a condition of weak or worn springs on the balance weights? what would be the best way to check?
Thanks Graham.
gt young

This thread was discussed between 15/03/2004 and 21/03/2004

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