Knocking V8

[denzil]

Hello again folks
 I ran the Disco up to temp on the drive  yesterday once its hot it starts to knock ,I think from mid/top of engine at tick over [750/800 revs] ,increase the revs to 1000/1200 the knocking appears to stop or perhaps I just cant hear it?. No problems when cold I changed the oil and filter made no difference .Do you think this is this the dreaded V8 liner problem ?.

[bogie]

Cam followers?????????????

[Range Rover Blues]

If it were the liners I'd expect it to be using water.  Like Bogie said I'd be looking at followers.

[denzil]

Hi warmed the car and let it tick over for a while yesterday[I am in the middle of changing the brakes],the engine now appears to be playing a tune it was a regular tap, then it stopped for a couple of seconds then started again.

Regards Doug

[JIMBOBLY]

if it keeps stopping the knocking noise now and then,i'd put money on it being the followers too.

[bogie]

The followers are turning mate.

[Range Rover Blues]

If you change them now the engine may be better for a while.  V8 followers are an odd thing, the cam lobe is ground non=parallel so that the follower is made to spin by the action of the cam lobe running off-centre.

The followers wear around the edges and rthe cam lobes wear along the edge, you can sometimes see a dirty mark where it wears.  This makes the follower contact patch move towards the middle of the follower.

Camshafts and followers wear together, a badly worn follower or followers almost certainly mean a worn cam too and often swapping followers is a false economy.

Talking of which, excessive fule consumption is often the first sign of cam wear!

Anyway, if your followers are sticking some of the time then spinning again you might be able to eek a year or so out of the existing cam by just swapping the followers, be warned though that the cheaper ones have a high fault rate, RPI now only supply OEM.


It is important that the follower spins because the spinning action makes it scoop up oil (apparently) which fills the follower making it expand to take up the valve clearence, not being full of oil makes the clearence too great and effects both valve lift and timing, hence the poor economy often experienced.

[denzil]

I think I will have to bite the bullet and strip the top end of my engine and see what has happend.I have a K&N cone filter to fit, when
I get a chance I intend to fit a sports exhaust with four branch manifolds. Suggestions as to the best cam to refit with this set up
would be appreciated.

Regards Doug

[MuddyMike]

How many miles has the engine done on the current cam? Has the oil been changed regularly? Both these questions are important because Rover V8s eat camshafts and followers if the oil is not regularly changed. If the cam has less than 60,000 on it and the oil has been changed regularly your problem may simply be sticky followers. This is quite common on Rover V8s that have stood idle for a while and can often be cured with a thorough flush.

For flushing add a liter of ATF to the engine oil (if the oil level is already high you should drain some off first) then take it for a steady run, at least 30 miles. Then change the oil and filter.

Does the engine have good oil pressure? Low oil pressure is another cause of noisy cam followers and can only be cured by re building the oil pump. These pumps use a pair of steel impellers in an aluminium  housing. Grit gets embedded into the aluminium  and wears the steel impellers, so both often need changing.

If new followers are needed you should change the cam and oil pump whilst the engine is stripped down, and if you are doing all that you might as well replace the timing gears and chain as well.

Mike

[denzil]

Hi Mike
Thanks for the reply, milage is about 118,000 I have got some service history not all , so its difficult to say how well its been looked after.I take your point I will change the oil pump and followers also take the heads off and regrind the valve seats.What cam do you
suggest I refit standard or other?.

[Range Rover Blues]

If you swap the camshaft for a performance one you need to chip the ECU.  Refit a stock 3.9 cam for about £70 or pay £350 for a performance one.

Cam followers can be done without stripping any further than the valley gaslet and rocker covers, depends hgow much money you want to spend.

[denzil]

Thank you Range Rover Blues,I will probably keep to a standard cam .I want to take the heads off and check the valves while I am
at it and for the cost of a oil pump I might as well change that as well.Should I use a genuine cam and followers or after market
ones?.

Regards Doug

[big tim]

Thank you Range Rover Blues,I will probably keep to a standard cam .I want to take the heads off and check the valves while I am
at it and for the cost of a oil pump I might as well change that as well.Should I use a genuine cam and followers or after market
ones?.

Regards Doug

Price of oil pump depends on which lump you have (i.e early or late spec) as later serp oil pumps are about 200quid i think for front housing or 75 for pump gears not sure on the price of early type. also might be worth checking your oil pick up pipe in the sump for either cracks or knackered gasket.

[Range Rover Blues]

RPI no longer supply after market follower because they have had trouble with them!

Also worth fitting an upgraded cam chain and gears, I think a pre-serpentine will take a duplex roller chain.  Not only can you then get the cam timing spot on but it will stay correct and not slip as soon as the chain wears.

Either way fit a decent chain.

Cam shaft, get a branded one or OEM, I'd ask RPI or someone what they use.

Whilst you have the heads  off get them skimmed.  An ali gasket is 0.5mm, the composite ones are 1.2mm so you can take quite a bit of head away if you refit with composite ones.

Also worth doing a bit of "fettling" within the head to improve gas flow, even if it's just a good clean up to restore performance.

Then fit new springs to the valves.

[big tim]

RPI supplied me with bearmach parts got them last september time had no probs up to now which is what we like.

[MuddyMike]

Hi Mike
Thanks for the reply, milage is about 118,000 I have got some service history not all , so its difficult to say how well its been looked after.I take your point I will change the oil pump and followers also take the heads off and regrind the valve seats.What cam do you
suggest I refit standard or other?.

I would stick with a good quality standard cam. At 118,000 if its not had the cam changed it will need one.

Mike

[Range Rover Blues]

RPI supplied me with bearmach parts got them last september time had no probs up to now which is what we like.

I don't think it was Bearmach they were refering to, more likely a certain brand we all probably know and avoid (I don't buy anything they make that has moving parts ;)).

[big tim]

RPI supplied me with bearmach parts got them last september time had no probs up to now which is what we like.

I don't think it was Bearmach they were refering to, more likely a certain brand we all probably know and avoid (I don't buy anything they make that has moving parts ;)).

Ahh i get you. You and me both RRB