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Broken Timing Gear

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Finally got round to opening up the timing cover on the old V8 out of Gemima to see what actually happened...looks like our hypothesis (from peering down the dizzy shaft) that one of the cogs had broken up was correct.





This was all we could reassemble of the camshaft cog. Guess the rest of it is in the sump.


As an aside, the quality of the timing cover casting was truly shocking. I'm amazed this was allowed down the production line...



As to why the timing gear broke up? No obvious reason. The hub of the broken cog is still securely in place, so it's not that it worked loose.

I did find a stray socket on the floor (you can see it in the second photo) - it's not from the set we were using, and it did make we wonder...I did the head gaskets on the engine shortly before its demise, and the dizzy had been out - maybe I dropped a socket in there and it had been lying in the bottom of the timing case just waiting to get thrown up into the gear? Tenuous, especially as there's a load of junk sitting on top of the engine so it probably fell out of that, but it makes me wonder... I'll never know, which is probably just as well - it'd be a bit of an embarassing way to finish an engine off... :blush:

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Oh Drat :(

Yep, its a common weak point on V8s.

For not much more than the std nylon gear on a steel insert rubbish you can get solid steel timing gears, 'real steel' and others do them plus duplex chain etc, some do complete kits

Fit and forget

Work the few quid extra


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  • 2 months later...

Well, it's been sat in the corner of my garage getting in the way for a few months, but finally got round to stripping the old 3.9 down today - along with a couple of mates, stripped it down completely, cleaned it up and stashed it in the loft in bits.

Amazingly, it was fine inside - couple of very minor valve strikes, no serious damage. There's a slight nick in one piston and two valves are chipped but not badly. Valve stems look to be okay, but we haven't removed the valves from the heads to be totally certain. The second piston had only had some carbon build up chipped off - no damage to the actual piston. Can't believe there was so little damage! :)

Cylinder 3 valves:


Cylinder 3 piston:


Cylinder 8 valves:


Cylinder 8 piston:


Photo's of the rest here, but they just look normal.

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