Single tap/knock noise

[STEVECHIM]

Hi

I wonder if anybody can help- I am in the process of buying a 1994 Chimera HC with 39K on the clock. THere is a single knock/tap on applying hard revs at tick-over as the revs pick up.
A (non-TVR) garage say it is "normal" for a TVR of that age, and is a lazy lifter- whatever that is! Could it be this ot ? timing chain.

Is this likely, is it serious?

I would appreciate help- I am very keen to be a Chimera owner.

Steve

[paulathome]

Sounds like you may have a leaking exhaust maniflod gasket.
When driven in a fairly high gear and you put your foot down you should hear a tick-tick
noise as the gas escapes past the leaky gasket.

You could also have cam or associated components on their way out.
If the engine is started from cold the hydraulic tappets can be noisey for a few seconds
until the oil gets the tappets pumped up. If this continues then the cam could be shot.
You really do need a second opinion from a specialist on the Rover V8.
If the cam is shot, it can get very expensive to fix. (new cam, followers,rockers etc, etc.)

Tread carefully and good luck.
Cheers,
Paul

[GreenV8S]

A single knock sounds (sorry) strange - are you sure it's coming from inside the engine, or could it be something external like the exhaust tapping something when the engine moves? Odd tapping noises aren't necessarily a problem, but this sort of one-off tap doesn't seem normal to me.

[STEVECHIM]

can anybody suggest somebody who could take a look? A home inspection of some sort.
the car is in wokingham.

[paulathome]

Sorry, well spotted GreenV8s a single knock.
Wonder if the engine mounts are knackered and the engines banging on something when reved?

[tahiti450]

paulathome said:

.... a single knock.
Wonder if the engine mounts are knackered and the engines banging on something when reved?

That sounds very plausible, have a look from inside the front wheel arches and check the clearance between the upper chassis rail / shock mount bracket and the collector of the exhaust manifold, there may be signs of contact between the two which indicates failed or sagging mountings, if the LH mount has sheared then you will get a thump during hard acceleration as the engine lifts itself of the mounting and then thuds back into position as the torque drops off. Also you will be able to see or at least feel the gear lever twitch as the engine and gearbox move. The mounts are not easy to get at but with decent long extensions etc I changed one of mine in about 40 minutes, by removing it complete with the bracket from the cylinder block and refitting as an assembly.

[STEVECHIM]

Thanks for your suggestions. Somebody suggested a hydraulic tappet or lifter as a possibility.
I think the engine mounts have been checked and are OK. I supppose the best thing would be to remove the cam covers and take a look at the cams/lifters etc?

Steve

[GreenV8S]

STEVECHIM said:

I supppose the best thing would be to remove the cam covers and take a look at the cams/lifters etc?

That's unlikely to show you anything useful. I think your next step should be either to go round the engine with a stethoscope and try to locate the noise, or ignore it on the basis that either it's harmless, or it will eventually become obvious what the problem is.

[M@H]

GreenV8S said:

That's unlikely to show you anything useful. I think your next step should be either to go round the engine with a stethoscope and try to locate the noise, or ignore it on the basis that either it's harmless, or it will eventually become obvious what the problem is and rob your wallet, savings account, and make you sell your children accordingly.

Agreed.