Metallic rattle opinions please

[JON1D]

Its good that you have someone local to you that has the experience of our vehicles. Its usually an old school garage which has been going for some time or set up with experienced older mechanics.
If they ask to plug into the diagnostic port walk away lol.
A garage that does maintenance on older Jaguars is always a good start.

[Paul H]

Sorry I haven't been on the forum for a while .

As the gearbox leak got worse and I don't have a lift, I took the car to Vince Gibbs classic cars near Banbury, who has worked on several cobra replicas over the years and happens to own a Southern Roadcraft cobra with exactly the same engine and carburettor as my setup, (he was the guy who diagnosed why my timing was all over the place about 5 years ago. (Rotating sensor mechanism was intermittently slipping on the distributor shaft)

Anyway he replaced the input and output shaft seals on the gearbox. He also replaced the thrust bearing and checked the clutch and sure enough my cobra does have a centrifugal dual friction clutch ,which increases clamping force ,while retaining a reasonably light clutch action .It has a circular  wire  ring with dozens of bent weights which use the wire as a hinge  and these are quite loose which must rattle when the engine is just ticking over. Once the clutch spins faster , the weights move out outward ,  applying pressure to the clutch plate . I discovered that if I park the car at an angle on the pavement , the rattle is noticeably louder ,but if I blip the throttle ,the weights slide outwards and the rattle goes. I hope that all made sense .
So as we couldn't find any other cause for the noise, we figured it must be that .

[chris27_blue]

Was this noise clarified?

Something similar myself. Not had a good look yet. Am gonna check for anything loose first, then thinking gearbox oil as have minor leak but noise doesnt sound pertinent, then thinking timing chain.

As per OP the rattle (tinny sound on start up) goes away when engine warmed up. relatively short lived - like couple mins or so. Sounds like a normal vehicle exhaust rattle.(I have no heat shields)  Concerned it may be timing chain. Only 8500 miles on chevvy engine.

[Paul H]

Manifold bolts were all tight, so I borrowed my "daughters friends Dads"  pit again and I stood underneath while he revved the engine and first thing I noticed was oil dripping out of the gear box , where it mates with the adaptor plate ,at the rate of one drop every 3 seconds, so a new rear oil seal needs fitting .

Still underneath the car, the rattle or grunching sound , is a bit like nuts and bolts going round and round inside a washing machine , although not as loud , appears to be coming from the clutch area ,but is I noticed  disappearing when the clutch is depressed  .

While I was at the Malvern show on the Saturday , I had a word with various people about the noise I was getting and one suggestion was to make sure the   adjustment on the hydraulic clutch slave cylinder was correct.
 
The other possible cause for the noise depends on what type of clutch I have on my 6.3 SBC/ Jaguar Getrag gear box setup. As I didn't build my AK, I don't know what type I have , but if it has a "Centreforce Centrifugal type ,the weights on the spring diaphragm may be the cause i was told .Having googled these clutches , as  the clutch spins, centrifugal force is applied to the weights, transferring through to the diaphragm to the pressure plate. This is how the Centerforce weight system increases clutch plate clamp load in respect to the RPM.
So for those guys who know about this stuff, is my setup likely to have one of these clutches and could this be my issue and if so, do I just put up with it as the clutch seems to operate fine or do I need to have the clutch out?

[Paul H]

Will do ,thanks Tommy.

[Tommy-boy]

Have you checked your exhaust manifolds are good and tight?

Even just a slight weep will sound very metallic and almost like someone tapping spanner off the block as such. It is a very metallic sound however it wouldn't explain why it sounds from under the car but it would explain when its hot only as the expansions from the heat.

Get them hot hot and give them a nip... fingers crossed it will be the problem.

[Paul H]

Julesdm,

I have a mechanical pump located low down on the drivers side at the front of the engine, which has a heat shield between it and the manifold, and i am fairly sure the noise is not coming from there, but thanks for trying to help .
I am using a neighbours pit tomorrow night , so i can get underneath it while its running to see if i can pin point the noise.

[Julesdm]

Where is your fuel pump?? When my red top gets hot, in a long traffic queue or after having parked up to get fuel, until cold fuel gets into it, it sometimes makes a metallic rattle sound!! Most annoying......it is located by the bell housing/below exhaust manifold, the only place i could secure it. And before anyone says it needs to be within 15 inches of the tank, it works fine and dumps enough fuel into my Double Pumper under extreme acceleration...

[Paul H]

I have hydraulic lifters which do rattle a bit until the oil pressure starts to build, which is normal ,but this noise is different ,louder underneath the car near the gearbox area ,like metal hitting metal .

Noise is still there with clutch up or down. This doesn't sound like the rumble of a worn thrust bearing Chris . I could do with finding someone local with a pit or ramp and get underneath while its rattling to pin point source of noise .

As you say ,maybe someone at the show might be able to identify the noise.

[ChrisP]

It could be the thrust bearing maybe? Is it the same with clutch peddle up and down?

Or, a loose sidepipe cover screw or cover? I've certainly had that rattling.

If it not solved by the time we are all at Malvern you can get 60 different opinions!

[Chris]

I have Rhoads hydraulics on my RV8 and sometimes get the slight metallic rattle at low rpm,
more so on hot days that have been > 35 deg C .
The noise seems to be exaggerated due to my side pipe setup .
May not be anything to worry about in your case, oil viscosity does tend to effect things in
this kind of way .
Chris.

[Paul H]

I recently took the Wife down to Dorset in the cobra on a four day road trip covering around 650 miles in all and it behaved perfectly. The weather was dry and hot the whole time, and we had a great time, except I noticed a reasonably loud metallic rattle developing while the car was ticking over, especially in long traffic jams. The rattle comes and goes and I can hear the noise in the engine bay, but it's more noticeable underneath the car, around the gearbox/clutch area and only occurs once the engine is hot. I cannot hear it if I raise the revs or while cruising and I cannot  see anything loose or moving .The clutch is working fine and engages all gears smoothly.
I have a 6.3 ltr SBC, coupled to a Jag Getrag 5 speed box.
Could this just be just noisy clutch springs or something more sinister.