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beanpole
06-03-04, 05:26 PM
Been running my Sumo around now since SVA and noticed something odd..

When you pull away, from start or after slowing right down to pull out of a corner , there is a tapping , (like a loose tappet), noise which sounds like a slight exhaust blow at the manifold.

On tick over you can just hear a slight tapping which disappears when warmed up, if you stamp on the throttle you just hear it for a second. If you slowly open the revs there is no tapping at all, so in other words it only occurs under load and low revs, under load at high revs, no tapping.

At revs there is no noise at all and everything runs very smooth and quite.

Could this be a worn rocker/shaft, the cam and followers are new. I had to replace the rocker assembly on the other side as one rocker arm had seized and broken.

Regards

Steve

Barry Davolls
07-03-04, 07:56 AM
Steve,
Assuming you are using hydraulic followers, you could have a faulty unit. It is quite common to have hydraulic failures even on new followers. Sometimes changing oil viscosity solves the problem.
If I were you I would invest in a mechanics stethoscope which are very good at pin-pointing the source of noise problems.
Baldric

kirklillis
07-03-04, 10:33 AM
'Mechanics Stethoscope'?

In the first instance, try using the old screwdriver method.

Take a long screwdriver and rest the tip of it on the area you think the noise is coming from. Grip the handle with the lower part of your hand so that the upper part of your hand forms a sort of cup with a hole between the thumb and your curled fingers.

Place you ear against your hand and listen. Move around the engine resting the tip against various parts of the rocker box (in this instance). You'll obviously need someone to help to replicate the 'load' conditions as you listen.

This is a very cheap and quick way to find out where noise is coming from. Not foolproof, but will give some indication.

Kirk

osgood
07-03-04, 10:43 AM
Steve, have you checked the pre-load on the cam followers? It should be between 20 & 60 thou. Thats the distance between the snap ring & the inner lip of the lifter.

I have a diagram if you need it. You can also get a large screw driver & place on the rocker cover while Engine running and put your shell like too it, to Identify location of noises Eric.

Barry Davolls
07-03-04, 10:46 AM
Kirk,
Yes the old method is cheap & cheerful but frankly in lot of cases useless.
A stethoscope costs around 6.50 these days & at that price, I doubt you would have have a more useful tool in your collection.
Baldric

kirklillis
07-03-04, 12:50 PM
Baldric,

Nuff said!

Kirk

beanpole
07-03-04, 05:08 PM
Thanks lads, I now feel a complete prat..

Did as you all suggested to listen for the noise, while I had my head down, I noticed I had put one of the exhaust gaskets on the wrong way round, one edge was poking out from the flange, allowing a small blow past on the other edge.

Hence the reason it only seemed to be under load..

Go on then have agood laugh, I did..

Steve


:} :} :}

osgood
08-03-04, 06:19 PM
Never mind Steve we all make mistakes mate. Use TVR composite gasket next time from Real Steel the are in bunches of two with bigger holes. The secret is being able to define the noise too a particular part in the engine and it location without any assistance from Screw Drivers and Doctors stethoscopes! I have both and there ain't no difference between the two!

As a retired Motor Engineer having also served an Apprenticeship in Light Engineering and Sheet Metalwork & flat cap and several SD1's we all make mistakes mate, supposed DIY mechanic's I've sht em!

;-) Eric.

kirklillis
08-03-04, 06:47 PM
Baldric,

On reflection I thought: "The wand is only as good as the magician that wields it!"

Kirk

Barry Davolls
08-03-04, 08:16 PM
I was trying to help someone with a problem, what are you guy`s here to do?

Baldric

kirklillis
09-03-04, 06:59 PM
Baldric,

My response was intended to be in support of your's.
I agree. While some of us have the benefit of formal engineering training, it is true that many (by their own admission) on the site do not. They are grateful for any and all advice received from helpful souls. While we may debate the usefulness of some of the advice supplied I don't think it is helpful for others to denegrate the efforts or the capability of those who supply it.

Email can be a wonderful tool, but can fail to convey 'lightheartedness' if that is the writer's intention. Best to stick to the point. I shall in future.

I'll write nothing more on the matter. I will continue to assist others where I feel I have something useful to add.

Kirk

STEVE G
09-03-04, 07:09 PM
Now I understand the screwdriver reference.
Steve G {-}
GE427-Rover 281ci.(300+BHP)

Barry Davolls
09-03-04, 07:33 PM
Kirk,
If I have miss-understood your intentions, I apologise.
Baldric.

osgood
09-03-04, 08:08 PM
Steve, :) :) :) :) whilst your on, could you tell me what the BHP & torque figures are for a standard 4.6. I have the disc but cant seem to find it, just maximum power @ 4,750 rpm Eric :tu