Engine knock but good oil pressure

[agtreves]

Hi Everyone and hopefully a Happy New Year! My 1970 2000 MkII Auto has developed an engine knock over the last two years. This happens until the engine has got really warm and also if pressed hard such as put into kickdown. Now the oil pressure is over 80 psi and drops down to about 50 psi on idling. Someone suggested that it could be the driveplate beginning to break up but I can't find any signs of cracking. Compression is good and even between cylinders so my thoughts would be a little end or piston slap. The question will I make it to the National this year or do I need someone to get the engine out and investigate?

[Dave B]

My money would be be on the autobox flexiplate, I think that's where I would start investigating. Its easier to drop the gearbox to have a look than take the engine out, the engine seems happy enough with good oil pressure and compression readings. Those driveplates can develop radial cracks from one or more of the four mounting holes and they do sound bad once that happens, but easily fixed with a new plate. I believe Chris Witor does an uprated one.
Hope you make it to the National, in fact I hope we all make it next year!

[agtreves]

Hi Many thanks for your prompt reply. I did not drop the gearbox out but I checked very carefully every bolt by taking out one of the plastic bottom covers and checking with a lamp and inspection mirror as I rotated the engine and there were no signs of any disturbance. Will this be enough?

[Dave B]

No, as far as I know, they usually crack from the bolts securing the flexiplate to the crankshaft, not the bolts fastening the plate to the torque converter.
If you Google image search "triumph cracked flexplate" you should get one two results to show what I mean!

[agtreves]

Hello again. Yes that is what I thought I was looking for. But I take your point that you can't see any cracks going towards the centre. It was also suggested that you could get a view by taking the starter motor out. The noise seems to come more from the front of the engine and not the bell housing.

[Sal]

Unrelated but related question.....

What’s ‘The National’ you talk about in this thread? I’m new to this forum and have a Triumph in bits but this could be a target for me to pull my finger out...

Is it a Triumph meet up? Where is it?

Cheers
Sal

[Dave B]

The "National" is a week long (or less if you wish) meeting of owners and people interested in the Triumph 2000/2500 range. Its not all car related though, plenty to do, day trips to local places of interest etc. The venue changes every year, but usually on a nice holiday park somewhere between Scotland and the south coast! Next years National is at St Audries bay in Somerset (Covid 19 permitting) in June/July 2021
You will get better info from the Register website https://triumph2000register.co.uk/ and https://triumph2000register.co.uk/gallery/
See you there.
Ps if you don't finish your car, you don't have to come in a Triumph!

[johnnydog]

The flexi plate on an auto produces a loud 'tinny' sounding noise which is normal whenever the starter motor is operated, but when the flexi plate develops cracks around the mounting bolts, this noise gets noticably worse. This noise can also develop into metallic 'cracking' sounds as the flexi plate moves / flexes during the operation of the starter motor.
As you say the engine has a 'knock' until warm, rather than a 'cracking' noise, I would be tempted to use the stethoscope method (a long handled screwdriver to your ear) on various areas of the engine block, cylinder head and gearbox whilst the engine is running to try and determine where the knock is coming from before you rip the gearbox out.