Hello, I daily a series and have been having a knocking problem for a few months now and can't seem to find the problem. The noise it the worst when cold and it vibrates the gearstick and make a very quick knocking. I have replaced the whole ignition system and timed the car to tdc which is factory spec for a 1979 3 main bearing peteol. Please could I have some advice on what else could be causing it thanks
steve2286w
Well-Known Member
Some times it helps to record it on you tube so peeps can hear , also useful to work out its frequency ie once per rev twice per rev etc
Is tappet gaps correct
Thanks will do the tappets soon. What would cause piston slap? But it seems like the worn main bearing from what it says on that list, is there a test or any other sign that it could be that
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steve2286w
Well-Known Member
On my diesel it was faulty injector spray pattern not sure on a petrol
Yeah I haven't cleaned my carb in a while I guess it could be fuel related
steve2286w
Well-Known Member
Just been googling it , it is the pistons rocking sideways hitting the bore due to excess clearance
steve2286w
Well-Known Member
You can whip,the sump off and remove main bearing cap to inspect bearing shells I think I did that at the time as I thought it was mains
Normally a nice white metal colour if worn you will see copper showing through
Cheers for all the help I'll be sure the next time I do an oil change to do that which won't be too long now
Check the engine mounts and gearbox mounts. I doubt its worn pistons, they don't knock, its more a rattle sound, same with little ends. Most knocks from bottom end wear get worse when the temp goes up as the gaps get bigger and the oil gets thinner. Wear on top end can go the other way as heat expands the pistons and valve gear and it reduces clearances. Check water pump and fan too.
Colthebrummie
Well-Known Member
How many miles has your engine done?
Col
Col
It's done 98,000 only been doing around 400 miles a year for the past 15-20 years till now
Colthebrummie
Well-Known Member
With kind of mileage on an old engine there is likely to be some significant wear in virtually all moving parts, especially the bores/pistons and big ends. When you rev the engine, does the knocking noise quicken in respect of the revs? If so, I'd suspect the big ends.
Col
Col
No the engine knock noise doesn't quicken, it's more constant at full throttle, but does get louder uphills. Doesn't knock on flat or downhill.
Colthebrummie
Well-Known Member
When you turn the engine off after a long run, do you get any sign of pre ignition?
Col
Col
No the car is fine just turns right off no signs of pre ignition
Colthebrummie
Well-Known Member
Stretch
Well-Known Member
So let me get this straight:-
Rythmic noise not engine or road speed related?
Noise does get louder with engine speed?
Messing about with timing has made some sort of effect?
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^^^^^^^^^^^If that is correct^^^^^^^^^^^
I would be considering something like a hole / crack in the exhaust system / manifold.
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As for timing there are kinda "two types" to consider. You've got spark timing and camshaft timing.
If you look in the workshop manual there is a section on checking the valve timing => This often gets ignored / overlooked - and to be fair is more often than not on a petrol engine less of a problem than it is on a diesel engine but worn cogs and chains do happen...
Rythmic noise not engine or road speed related?
Noise does get louder with engine speed?
Messing about with timing has made some sort of effect?
####
^^^^^^^^^^^If that is correct^^^^^^^^^^^
I would be considering something like a hole / crack in the exhaust system / manifold.
#######
As for timing there are kinda "two types" to consider. You've got spark timing and camshaft timing.
If you look in the workshop manual there is a section on checking the valve timing => This often gets ignored / overlooked - and to be fair is more often than not on a petrol engine less of a problem than it is on a diesel engine but worn cogs and chains do happen...
