i would check the cam ,timming gears,chain,tentioner,key in gear
front pully

i too would inspect the timing chain assembly. maybe worn tensioner.

Yeah I'll have to pull it all down again I guess.


Have a spare flat top A12 ready to go in that I might throw in until I can be motivated enough to pull the noisey one down again

check the compressed height of your valve springs for coil bind (shaved head, high lift cam- srings can't compress enough?)??

Springs are good. Comp ratio is quite mild so although there is a high lift they're lifting well and clearing well.

Ran into another dilemma but I'll keep that one quite that was due to my stupidity rather than the part failing on it's own (I broke it).

Cam lobes are fine.

Pushrods are straight.

Cam sprocket is fine.

Timing chain looks fine.

When I said the noise comes and goes I meant it comes and goes through the rev range as opposed to coming and going on separate running occasions. After speaking with sikyne, we both agreed it has to be the crank/main bearings/excess clearance.

Thanks Simon for the help & sorry to bug you!

Because I'm so broke after Christmas I'm measuring everything myself and if the clearances are suspect I'm replacing the crank with a stock factory item and ditching the knife edged crank, it'd probably help with driveability anyway.

Should finally have a confirmation on the cause tomorrow.

if it twer' the crank couldn't you just chuck a set of nice fat oversized bearings to go in there once it's been spun up into spec

Yeah sorry I've muddled it all up.

Turned out to be a conrod (big-end), and at the same time I didn't like the look of the shells that came out of the main caps, looks like things were a little too spacious.

Started the car last night after the knife-edged (now in need of some professional care) crankshaft was replaced with the factory item. It was good to feel a little more inertia/momentum with the heavier crank.

So it was a con-rod all along, I feel a little stupid! The last con-rod knock I had was much more obvious and loud so I guess that why I didn't consider it initially. Thanks for all your input guys. Managed to salvage the shells before they were about to spin and become molten metal in my engine.

So I guess the cause is still a little vague as the engine was pretty fresh. When it was dummy assembled professionally the word was that the measurements were all good.

The oil was a little while to come up last time and this time I ran it for many, many revolutions (no comp just starter motor) to get everything nice and lubricated, pressure was once again reading well. I guess I wasn;t as nice to the engine when I got it on the road either, the breaking in period wasn't really adhered to.

So I took it out this morning, had a slight exhaust rattle so I fixed that. Took it out this arvo with everything seemingly running nice. Went round a corner, paused to let the traffic clear and then started off again nice and carefully. Sudden 'snap' noise and I'm at a standstill with the engine spinning but no drive.....all gears gone.

So now I've managed to #OOPS# my gearbox. When does it stop?!?! God I love Datsuns

lucky some parts are cheap
wot are u doing with old crank?

Melting it down and casting it into little sinkers to use when I go fishing


Nah, seriously? I'm not too sure. It's just sitting there at the moment. Send me a PM if you were interested in it. Could take some pics etc.

Chris

pm sent