Engine Knocking - Bad!

[Gduplock]

Need recommendations for someone to carry out diagnosis and engine rebuild for 1968 911L Sporto preferably in South East UK. 118K miles but top end was rebuilt in 2012 at 106K. Now deep knocking on idle . Not alternator bearings. DSD Motorworks did top end. How do people rate them? PM me if you like. Graham

[911hillclimber]

Did they replace the chain tensioners? Should be on the rebuild list.
When these fail the noise is very loud and very disturbing and not a knocking like a big end bearing that changes frequency with engine speed.
The rattle is truly gut wrenching (personal experience) and best to not drive the engine at all.

A good specialist will be able to say if the tensioners are suspect if you put your phone to the noise and let him listen.
You have old people in your general area. google is your best friend.
If the tensioners are collapsed then they can be changed with the engine in place, could be £1000 if pressure fed tensioners fitted as replacements.

If the deep knocking changes with the engine speed then it is a total engine strip exercise.
Good luck with it, let us know how it works out.
Hope this helps.

[Mike911scrs]

HI Graham (top post)

is the noise just at idle when hot-hot and the oil pressure is 4 bar at 4,000 rpm,

if so there could be some wear in the Ally inter-gear gear that drives the timing chains, if the Ally gear has some wear on it or the inter- gear bearings have some wear, you can get a dull constant knock at idle and it is not there in the upper RPM, where as a B/E bearing wear would be more notisable with more RPM and a quick blip of the throttle

if it had the later oil fed pressure tensioners fitted at the top end work , the extra load could have worn the Ally gear some more, was the chain drive wheels inside the engine inspected when the top end was done, also the Ally gear can also could have been checked at the same time

if you get the engine hot and making the noise, switch it off and take the key out, then take a 19mm long spanner a turning the engine onto TDC/Z1, then move the crank pully back-forwards and feel the play/clunk between the crank and the inter-gear Ally gear, if any?

if you still think it is a B/E bearing, then get a new oil filter, take the old one OFF the tank and with a small hacksaw cut the top off and inspect the filter inside for and bearing material.

let us know how you get on

regards mike

[911hillclimber]

Hello Mike! (Second Graham), hope you are well.
First Graham, now you know where to send your engine to.

[MikeB]

I had a tappet come loose on me once, which also makes a reasonably worrying clatter, as JWhillracer may remember. That would be the easiest to diagnose ( slip the rocker covers off and look for a loose locking nut) and cheapest to fix.

[Gduplock]

Thanks for your thoughts everyone.

The noise starts gradually a few seconds after the engine starts from cold, quicker i think from warm start. It increases in frequency as engine revs increase until it is continuous.

I think I have managed to load a clip of the idling sound below. Apologies if it doesn't work.
Graham

https://www.flickr.com/photos/165485618 ... ted-public

[DarthMJH]

I think mine sounded similar when the cam tensioner broke away.

[911hillclimber]

Yes, personally I would remove the cam chain covers and look at the tensioners, look at the rockers too esp on that side.
All easy if you are ok with spanners. All gaskets needed are available from type911 separately too.

Reset all rocker clearances.

Let us know.

[Mike911scrs]

HI Graham

I see from your (not working) Vid link that you have a early Ally case engine in your car, is it the original engine?

the noise could be the inter-gear not been or needs the adjustment checking, while you have the chain case covers off checking the chain tensioners, just check the end float on the inter gear, as it may need adjusting, if someone has fitted a Std gasket in there not realising

have you had the Dist cap off and checked that the insides of the dist have not come apart and making the noise, as you have the Vid starting on the that side of the engine?

regards mike

[Gduplock]

Thanks for all the advice, I am not confident enough to take chain covers off.

Sorry about vid, if you are patient you can get it to work.

Graham

[Gduplock]

Thanks for all the advice guys.
Failed chain tensioner on 1-3 bank was the problem. Luckily Chain locks had been fitted at last engine works so chain did not come off cauing valve/piston damage. No need for engine out as said above.
Picking up car tomorrow.

[KS]

Phew! Lucky escape...