Top end rattle on Rover V8??

[AndyS2]

I've had an annoying top end rattle on my 3.9 V8 for a while now that I always thought was either a worn rocker shaft or rocker arms. But I've noticed recently ( mainly due to a broken CD player! ) that it noticably worse when it's cold and it gets worse under load. Now I would have thought that if it were rocker gear related then it would be constant regardless of temperature or load? So could it be something much worse like piston slap? It dosen't burn much oil and a compression check shows all is ok.
I dont want to fit all new rocker gear if it turns out it's not that, so has anybody got any ideas??

Andy

[greenv8s]

Are you sure it is a mechanical noise and not just a blowing exhaust gasket? They can produce a very metallic tapping noise.

[AndyS2]

I'm fairly certain it's mechanical, the exhaust was blowing a bit back and I spent ages sealing it up, so I know what that sounds like and it's not that sort of sound. The odd thing is, it really does only show up under load, I can rev the engine whilst holding a 'stethoscope' ( i.e. screwdriver! ) to the rocker cover and only just hear it, but as soon as I drive off its quite obvious.

[kevinday]

Silly question maybe, but is it pinking?

[wedg1e]

Leaking cam follower?

[2 sheds]

If it only produces the noise under load, i would say most likely to be exhaust gasket leaking, as Peter said it will sound very mechanical nothing like a normal exhaust blow.
Tim

[AndyS2]

Thanks for that, I'll check for leaks on the exhaust manifolds at the weekend but from what I can remember all the nuts that hold them on are really corroded so it should be a fun job!!

Andy

[Boosted LS1]

Is it a high mileage engine? If so it could be piston slap.

[rev-erend]

Or perhaps you should just fix the stereo...

[v8 racing]

Hi andy due to the pushrod design these engines can knock a lobe out of the cam and the sound travels up the pushrod and sounds like its a rocker arm, have you noticed a power drop off at all?? and also is your oil pressure still good? low oil pressure will not allow lifters to pump up properly, the load bit spooks me a bit though!!

[AndyS2]

Here's a bit more history on the engine, it's done 114,000miles and the cam, cam followers, timing chain and sprocket were all changed about 5000miles ago. judging by the state of the inside of the engine it's not had regular oil changes as it's fairly sludged up, but the mechanic who swapped the cam said it was about average for the age and mileage. The old cam had indeed had a couple of the lobes knocked off almost completely and it ran 100% better with the new cam. It hasen't got an oil pressure gauge so I can't check that but it's another thing on my list of things to fit.
I don't think the noise is pinking because it does that aswell!! but only at larger throttle openings, I've tried setting the timing by the book and 'by ear' and neither got rid of the pinking. The only way I got rid of it was to retard the timing so far that it was as flat as a fart, so I'm thinking it really needs a top de-coke. Really I just wanted to get rid of this rattle and sort the engine out properly in the summer when I won't be using it.
I'll start this weekend by checking for leaks on the inlet and exhaust side as that sound quite cheap.
I'll let you know how I get on and thanks for all the ideas

Andy

[AndyS2]

DOHH!!

I guess you guys were right, it was an air leak!! There was a slight leak from the exhaust, again, but more seriously there was a leak from around the base of the plenum chamber, so I took this off and also the inlet trumpets and re-sealed them both. It now runs 100% better, there is still a slight tick but I can live with that until I get round to doing a full top-end re-build. I never realised that an air leak could have sounded so metallic, if it wasn't for your helpfull sugestions I'd probably have half the engine in bits by now looking for worn parts!!
I bought a full set of rocker gear off of e-bay at the week-end for £36!! Only done 16K and looks like brand new, I'm keeping my eye on a few sets of heads at the moment so I can re-condition them and fit all the new bits at once.
Thanks for all you help

[Steve_D]

You can fit the individual exhaust manifold gaskets upside down. At first glance they look symetrical but they aren't. When upside down one side of the gasket is sticking into the port and only sealing the joint by about 1mm.
Ask me how I know.
The relultant blow has an incredably metalic sound to it. Search for it using a bit of hose pipe rather than a screwdriver as the screwdriver only 'hears' mechanical problems.
Steve