With regard to the frequency of the knocking, it is not constant but when it happens it is regular (ish). Having run the engine with the rocker covers off, trying to source the noise, it appears to be timed to valves opening on predominantly cylinder 5.
The noise completely goes away for a good period, but then returns.
The RR has just towed a large caravan 50 odd miles, with no problems and no noise to start with, but knock by the end of the journey.
The car is away at the moment, I will have another listen when it gets back.
Thanks for all the thoughts and suggestions so far.
Andy
Knocking on 4.2 in RR Classic Help!!!!!!!
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Could be a lazy cam follower which is not recharging after a lift cycle when to oil is hot and thinner.AR018 wrote:With regard to the frequency of the knocking, it is not constant but when it happens it is regular (ish). Having run the engine with the rocker covers off, trying to source the noise, it appears to be timed to valves opening on predominantly cylinder 5.
The noise completely goes away for a good period, but then returns.
The RR has just towed a large caravan 50 odd miles, with no problems and no noise to start with, but knock by the end of the journey.
The car is away at the moment, I will have another listen when it gets back.
Thanks for all the thoughts and suggestions so far.
Andy
On the subject of piston slap, I assume this engine has not been rebuilt recently. The RR 4.2 has offset piston pins and if a piston is in the wrong way round it will slap more. However any noise from piston slap would probably be worse when the engine is cold and change with load and unlikely to be intermittent.
Regards Denis
1950 A40 Devon Hotrod with 5.0 twin turbo RV8.
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!
I have just cured what I believe to have been a slipping liner on my 4.6.
It suddenly developed a heavy knock, checking the shells proved they were ok.
Stripped the engine completely and took the block down to Chesmans, where it was heated up, all the liners were checked and number 3 pulled straight out. As it was slipped back in quickly it made the exact noise I had witnessed.
Some of the other liners showed signs of rotation at some point ( the machining marks on the deck were not aligned with the marks on the deck), none of the liners were lower than the deck, but a couple of them were slightly proud (you could catch you nail on them)
I could find nothing else wrong with the engine upon inspection, and now its down around 150 miles since the rebuild it is so far so good!
Edited to add: The day after the knocking started, the engine was run and the knocking was not apparent. It started again after the engine got nice and hot.
It suddenly developed a heavy knock, checking the shells proved they were ok.
Stripped the engine completely and took the block down to Chesmans, where it was heated up, all the liners were checked and number 3 pulled straight out. As it was slipped back in quickly it made the exact noise I had witnessed.
Some of the other liners showed signs of rotation at some point ( the machining marks on the deck were not aligned with the marks on the deck), none of the liners were lower than the deck, but a couple of them were slightly proud (you could catch you nail on them)
I could find nothing else wrong with the engine upon inspection, and now its down around 150 miles since the rebuild it is so far so good!
Edited to add: The day after the knocking started, the engine was run and the knocking was not apparent. It started again after the engine got nice and hot.
