Hi all,
would it be possible to replace a small end con-rod shell bearing from the sump end of a CVH engine? My engine\'s making a bit of a knocking noise on tick over.
I\'m not sure what the throw of this engine type is, therefor not sure if the crank pin will provide sufficent clearance for this job. If not I guess it\'ll be a head removal and piston/conrod removal from the head side after taking the sump and conrod cap off.
If the latter, is it worth renewing the piston rings on one piston whilst I\'m at it?
M.T.I.A AGB
|
Only the big ends / crankshaft have shell bearings. These can be replaced without removing the head.
To replace a small end means removing the sump and head and replacing the piston. A new piston comes complete with rings anyway. Can't remember if the CVH engine has press fit gudgeon pins, if they do, the best bet is to take the con rod and piston to an engineering shop to be fitted.
It should be ok to fit fit just one piston, although a purist or pedant might argue otherwise.
The only engine I've come across where the pistons can be removed downwards is the old Renault 1.4 as fitted to Volvo 340's. The big end cap was too big to pass through the bore, and the lower part of the bore was tapered to facilitate ring compression on re-assembly.
|
Thanks for the reply 'none'.
I guess you could call the bearing in the small end of the con-rod a 'bush' and not a shell bearing.
The company I work for bore's the small end bush to a ±0,0125mm tolerance for an almost transision fit to the gudgeon pin. I might find this an issue as you say. This didn't cross my mind, and I will now firsty find out if the blokes in the works tool room could bore my con-rod out accordingly.
I would not expect to have to replace a piston. The gudgeon pin will either be held in by internal cir-clips or if an interference fit, this would be removable and re-pressable.
In any case, if the piston will not pass the crank in this engine design, I'll be having a major job on my hands.
Many thanks
TonyBee..
|
Tony, if the gudgeon pin is a press fit, it'll be pressed into the con rod, the piston will be a sliding fit on the pin. I can't see the interference fit loosening but if it has it means a new con rod and piston. If it's the piston loose on the pin, both will have to be replaced. If the con rod small end is a pressed in replaceable bush - just remove and replace. (A fairly skilled job that might entail a bit of reamering). I wouldn't consider machining the con rod.
|
|
|
|
You certain it isnt tappets or camshaft. These. including non turbo models suffered this. not personaly known one to get small end knock
big end yes. Just wondered?
--
Was mech1
|
|
|
>>If the latter, is it worth renewing the piston rings on one piston whilst I'm at it?
Not from any purist point of view, just laziness; I would have just thought that having got it all apart then you might as well do all of them - I'd consider the big-end shells and have a close look at the valve guides as well.
I'd also be amazed if you can do it from below.
|
|
|
Its unlikely to have one small end being gone.
Unless oil hasnt been changed as often as needed. But this usually affects all parts.unless oil pump faulty/blockage. I cannot see why small ends would cause a prob.It isnt a good idea to replace piston rings on one piston only.as it will cause an imballance between other cylinders depending on wear between them. Ie it will run rough. Just my thoughts
--
Was mech1
|
Was mech1,
how about the big end bearings or even the main bearings haven gone? Can these go one at a time? If so can I replace them individually or does the whole set need doing?
AdyBee..
|
Mostly the reason for big end/main bearing failure was because engine revs where taken to rev limit/ on RS most thought the oil pump would cope with continuous high revs/ mistake made was that without mods ie higher oil pressure pump.in continuous mode wasnt able to cope.starvation of oil supply caused big end failure/mains. Both will cause loss of oil pressure.what you mentioned didnt make this point.What I need to know is. is the noise from head or lower down ie cylinder block/bottom off block?. to answer your point if you take sump of after jacking up. and making safe.you will have full access.use a manual to be sure.But its unlikely one big end/main bearing will pack up
--
Was mech1
|
|
|
|
