K10 weird knocking

[Phil_the_Chill]

I can hear a new weird knocking noise on my K10.. it is more like a tapping.
Sounds like the left hand side of the engine. Not wheels.. it will do it when still. It seems to need to warm up before it starts... it is too slow to be a piston etc.. it is regular like a metronome and in proportion to the revs but like 1 tap per second.. it speeds up a little with revs.. then slows down again..
when the revs fall below a certain level.. it cuts out.. it is as if there is some engine management device that cuts in at low revs.. the engine drops suddenly lower then.... the tapping stops. I think the rev dropping is the normal car function.. but this tapping.. it's new!
I did rip out the radio aerial lead on the day it started and I wonder if I accidentally dislodged some other wire than may be involved? I like the K10 not least due to its lack of wonderful engine management rubbish .. I am aware of the an anti-run on valve? and maybe some rev booster linked to power usage.. but .. I just can't figure this noise out and how it could be related. Baffling.. it is quite a sharp mechanical tap.. like the starter motor trying to engage and getting flung back or something (one imagined scenario)..
I will have a close look under the hood and try see something moving...

help!!

Ta

actually I will make a recording for future reference!

 

[Phil_the_Chill]

I took it to local shop for mechanic to listen.. he simply pulled off the vacuum line and it stopped. He concluded that the advance mechanism is broken and I need a new distributor.
I don't want to question his expertise but it could also be that the timing is too advanced perhaps? When I got the car I found the thermostat was mangled out of all recognition.. permanently open.. the car ran cold. Maybe this was to prevent the pre-ignition when it heats up? The knocking comes from the distributor.. there is a big kick every now and then that seems to communicate itself down the camshaft to the distributor.
I could either visit the scrapyard for a distributor or get a new strobe timing light? My gut feeling is check the timing first ... plus.. I will need a timing tool in any case.

 

[Slim]

i had the very same problem. you can either replace the vacuum capsule, or replace the distributer. Either way, it was to come off. If your car has points, then this is a good oppurtunity to ditch them and get a later electronic distrubuter.

a word of advice though - if you get another distributer, check the vacuum unit works properly:- suck the end of it to build up a vacuum, then put your tongue over it to see that it holds the vacuum. When you let your tong off, you should hear everything return to normal position. If you cant hold a vacuum that means the unit is knackered.

When you've finaly found one that works, and i warn you that most K10 ones are duff, you'll need to set your timing back up anyway.

 

[Ed]

Good advice from slim except for mecahnical wear is usually worse than the vacume actuator failing. I have not myself come across a broken one. Another source for the noise could also be a loose rocker shaft under the rocker cover. This is quite common.


Ed

 

[Andrew]

The drive between the camshaft and distributor can tap as well, supposedly that is what the small piece of metal that goes missing is for.

 

[Slim]

but if it stops when the vacuum pipe is pulled off............it indicates to me that it's the capsule.

I can show you a handful of capsule's ed that have falied. The advance mechanism in the distributer still moves free enough, but the capsule is punctured to doesnt hold a vacuum. It's more comon than you think having a duff vacuum unit, however, not many of them click, although mine used to, and so did pete riste's on his K10.

If the vacuum was not mentioned, i'd personally have suggested that it sounds more like the main bearings knocking a bit. certainly not uncommon in higher mileage MA engines!

 

[Ed]

Im not saying its not possible slim, just not happend to me

 

[Phil_the_Chill]

In the end I retarded the timing a little and it went away.
I suspect it was overadvanced a tad.