Thread: new noise after V8 cam install

i have a friend with a 96 Discovery, 3.9

at idle it has a destintive knocking sound,
when i asked how long this noise had been there, the responce was, it's always been there, they have had the vehicle for over 8 yrs!
I thought straight away it was a slipped liner for sure,
but the noise goes away when the engine is revved, and runs like a clock, uses very little coolant.
It was diagnosed by a fairly cluey mechanic as excess end float on the cam.

Originally Posted by mike 90 RR

Just start the motor in the morning and let it idle to warm ... Don't Rev it at all .. just let it idle...

let it idle for 15 minutes from cold start - initially noise did not appear to be present at all. after few minutes had just the slighest hint.

after 15 minutes revved it a few times and let it idle and the noise is there. not as loud as after been driving.

so guess that answers part of the question. (though what does it mean i dare ask?)

if crank is turning 700rpm then one revolution is 11.6 times a second
if cam is turning 350 rpm then one revolution is 5.8 times a second.


if it was going to be either of these i would opt for the cam frequency but even that would be faster than what i'm picking up.

if this problem/noise is something that was a direct result of the work done then i would have to take it to a mechanic for a professional opinion so would take it in to JC next week. although there is an incredibly high correlation between the noise starting and the work which was done it is not guaranteed the two are related. i would like to say it is still interesting trying to diagnose it but at this point in time i'm over it. (hence my thoughts turning to a new vehicle with 5 years 200k warranty in an earlier post) though, what usually happens, you end up getting over it and accepting the things that go along with owning an older land rover though i'm getting closer to not holding up my end of the arrangement. ie the car provides the problem and i provide the solution and fix it! i view a car as a tool and if you end up spending too much time working on the tool then it takes away from the time you are meant to be using the tool to do things with......aaaaaargh. my two discos before this one were great.

milld - good idea. i've got a wireless broadband connection so not much chance of listening to video without it taking too long no matter what speed they reckon you get. if i can still be bothered will go into library next week and use their online machines.

[QUOTE=pibby;1467796]let it idle for 15 minutes from cold start - initially noise did not appear to be present at all. after few minutes had just the slighest hint.

after 15 minutes revved it a few times and let it idle and the noise is there. not as loud as after been driving.


Don`t know what this tells , other than heat doesn`t have alot to do with it .

Though my interpretation may differ , be interested to see .

I`d suggest .... and i understand you dont think the noise is as high up .

You say it`s a slow hollow knock , thats 1 for cam knock .

When the noise is present , run the engine slowly up past 1500 rpm , i understand it`s not easy to hear but if the noise disappears and is not just ovecome , thats 2 from cam knock .

With the noise`s not present ( but if there , still may show as stronger ) , not moving , at idle , load the engine lightly , if your able to make the noise or make it stronger , that`s 3 for cam knock .

The reverse of the above is you rule out cam knock .

Your description of the 4.6`s history says it may be that the cam retainer that is factory for a 4.6 was not used because it was a new engine and one of the reasons for my Question about its history .

There other way cam movement can be limited is by used of special bolt with a nylon button on its head , if the place that fitted the cam used one they would have invoiced it , i`d think .

The 4.0 in our 85 RR has a cam that came from the same place as yours , it also was new crated , has roll master set and is not retained as was intended factory .

It differs in that it uses the old style timing cover and oil pump but has never had any knocks .

been listening to it again this morning - i just can't hear anywhere near 5.8 'knocks' per second at idle. at times it can be down to 3 'knocks' per 2 seconds or even once per second.

i had a listen to a vid which was purported to be cam knock. it was on a twin cam motor and the sound was very similar to mine.

so rechecked the points PLR wrote :

"You say it`s a slow hollow knock , thats 1 for cam knock ."

yep, definitely a slow hollow knock.

"When the noise is present , run the engine slowly up past 1500 rpm , i understand it`s not easy to hear but if the noise disappears and is not just ovecome , thats 2 from cam knock ."

in the main this is correct. a couple of times could hear it up to 1600/1650 rpm but when revving it is weaker and i would say disappears and is not just swallowed up by the increasing engine sound.

"With the noise`s not present ( but if there , still may show as stronger ) , not moving , at idle , load the engine lightly , if your able to make the noise or make it stronger , that`s 3 for cam knock ."

at idle the noise is there just about all of the time. i put a figure of 90% on it earlier, but i reckon i'll up that to 95% of the time. give it an ever so light increase of rpm and the sound is definitely still there. it's frequency will generally increase marginally when doing this. i wouldn't say it gets louder - it seems to be at its loudest either just sitting there idling or when doing this testing when you come off the accelerator pedal to let the revs drop.


it really is an omnipresent sound. now a bit of narrative has been built up i will offer the following interpretation so please feel free to say ‘that’s bollocks”. when listening underneath with the hose on the intersection of the sump and the bellhousing the noise seems to move distant then come back. the frequency and other attributes remain the same but the immediacy to the point where the hose is being held lessens and then returns. so if there was some type of thrust washer or retaining plate absent can this give grounds to reading this sound as the camshaft bumping (thrusting??) up against one end of the motor till it hits something then likewise in the opposite direction.


well, it is seemingly likely that it is the cam knocking. so the obvious question then becomes has this caused any damage and what rectification would normally be required?

so shall pop off to see jc during the week after as i think he said he's back on the 5th when i was chatting to him the other day.


PLR - the motor has the 3.9 timing cover so i took the old cam in to the camshop to ensure they supplied the correct replacement cam. i remember there being possible confusion around the nose of the cam and whether it was the 4.6 nose or the earlier nose etc. this was after the guy who owned the worskhop spoke to the cam guy, I didn’t want a stuff up. as it eventuated, they reground the cam so that eliminated any confusion. what cam did you end up going with? there was one cam underneath the grind i got wrt duration and the bloke at the the camshaft place said he has supplied plenty to a land rover worskhop in melbourne. from memory, it was one more notch up on being a torque cam than the one i got (mines a 259b from memory). i'm waiting for a cable to get fabricated so i can connect my kickdown and be able to put the boot in. having to drive like an old lady till that gets done but with the cam and the thor manifold i've put on i couldn't ask for any more go and this is on injected lpg. the reality is i rarely go over 3k rpm hence my question about which cam you went for as my understanding is the lower the duration it pulls the torque lower. the old plenum i believe had peak torque around 3k whereas the thor has it around 2.7k. so with the cam i've got in currently i'd imagine it's even lower and lower is better as she's got plenty of go and just doesn't need to rev out.

G`day ,

I`m only suggesting it may be cam knock .

If you feel it could be then you should really remove the serpy belt and run it for a short time and listen . If it goes it`s not the cam .

There was a LR tech service bulletin in 1995 for 1994/5 3.9 Disco and RRC with serpentine belts it was about the fitting of the nylon button bolt for cam knock . These vehicles one would consider wouldn`t have do many ks .


Keith is , i would think , the same bloke i spoke with in 2004 when i fitted a 259a ( i think yours is a 328B ) back then there was nowhere near the easily obtained information that is about now . He explained which of their cams were for torque and which were for horses . I went through all the off the shelf cams and their figures as well as Wade and Tighe and compaired as well as i could with the factory figures i could find ( which weren`t easily found ) and decided that the 259a was what suited . As well as what you compaired i also compaired the open/close time of the valve because this also has an effect on what , when and where things happen .
I wouldn`t do a comparision again but i think if i ever have the front of it i will advance the timing a couple or more degrees .

plr - no worries. thanks for your input. i know you're only having a stab at what the prob could be based on the symptoms i have offered.

Originally Posted by PLR

If you feel it could be then you should really remove the serpy belt and run it for a short time and listen . If it goes it`s not the cam .

please excuse my lack of knowledge on this, how does the belt contribute to the knocking (if that's what the noise is)?

Originally Posted by PLR

Keith is , i would think , the same bloke i spoke with in 2004 when i fitted a 259a ( i think yours is a 328B )

i reckon you're right, i went and rechecked a post i made at the time. i think the 259 keeps sticking in my head as i was going to go that one then at the last moment went the 328. i thought they are both moving in the right direction away from the pc216 (which was in the motor) so go midway. i remember after the exercise of choosing a cam that duration and lift were about the only things that i could draw a line from to how they would impact the motor. i never could get my head around the exact impact of slight changes in the degrees at which the valves opened and closed. i remember the bloke who owns the workshop where the cam was installed used to work with holden and was involved with cam testing. he said it would be day in day out of changing cams multiple times during a day to see how they performed/compared. so if those guys with all that money and computer modelling still had to keep playing around with cams to see how theory related to real world then it was a bit of a black art in my mind and i was never going to understand it in any detail.

Originally Posted by PLR

if i ever have the front of it i will advance the timing a couple or more degrees .

is there something to be gained or something to be overcome in doing this? i ask about the 259 as i'm assuming if the cam is knocking that it has to all come out again so if that's the case then i may as well go the next cam along which is the 259a. as keith said at the time, he has supplied a lot of them over the years.



philipA - has your noise gone and disappeared on you again and everything's apples?

philipA - has your noise gone and disappeared on you again and everything's apples?

I don't drive it much but the next and most recent time I drove it, it was fine.
The cam knock sounds correct as we both have experienced it after changing the cam. So by twisted logic it's the cam, and cam knock is harmless but annoying.
It can be fixed in mine with a cam button and lots of patience to adjust it, but I for one am not spending hours to do it. Your motor has provision for a guide plate on the front of the block, but the cam may have to have a surface machined on the front to match.
Regards Philip A

Originally Posted by PhilipA

but the cam may have to have a surface machined on the front to match.

Interesting quote that, Phillip ....


.... Just to add to the Cam knock subject ....Funnily enough, at the same time Pilbby posted this thread, I was doing the below .....



I've got this D1 that starts up from cold and is quiet as a mouse.
As it gets to running temp a "knock knock" sound appears.
I used my screwdriver to ear method, and tracked it to the front of the crank, at the sump level.

It sounds like a conrod bearing and is in tune with the Cam cycle, I was even thinking the slipped liner thing

A test found the cam chain was stretched 9 degrees ..... sounds feasible
So I changed the cam chain

Finished the job and started it up .... As usual, Quiet as a mouse from cold ... but as soon as it gets to running temp ..... No knock noise from the crank area ....



Instead, it's been replaced with a slight knock near the top of the motor



A listen through the screwdriver, gets me to the lower middle of the intake valley ..... I believe it's Cam knock ....
..... I had disregarded checking the end float while the timing cover was off ....

Cheers
Mike