Cam wear advice

[LewG]

Hello,
Currently in a bit of a dilemma as to whether to replace my cam. The car is a standard 4 litre, double valve springs but no pocketed pistons, has done 72k and as far as I can tell has never been cracked open before. The bores etc. are in superb condition with no 'lip' and hone marks clearly visible.
I got a DTI directly onto the cam lobes this afternoon and am getting pretty universal readings with no abnormal results, all between 6mm to 7mm. Does anyone have any experience of this? I had a quick chat with Rob at V8 Developments and he was very honest in saying that sounds about right, obviously I'm limited in cam choice with my engine spec anyway but I thought I'd put it to the collective knowledge of PH before putting it all back together.

[ch427]

I suppose it all boils down to how much you want to spend, the only cam i would probably consider is the MC1 and thats only because its the one that has the most positive feedback from owners.
The standard cam which im guessing is a fast road from kent must be fairly hard to beat, TVR couldnt have got it that wrong surely?
I like the characteristics of the standard cam and paying out over £500 just to gain a few bhp here and there does not make much sense to me, if its not worn and your not chasing every little bit of extra performance then leave alone.

[fausTVR]

Forgive my ignorance here, but is 6-7mm deflection down to wear, I was expecting 12-13ish.

[phazed]

I'm not sure what the 6-7mm is measuring but would have thought that whatever the measurement is, it should be precise oh within a few thousands of an inch, (or millimetres).

[J400GED]

Bobby Shaftoe said:

The rockers multiply the cam lift by a 1.6:1 ratio, so 6to7mm at the cam is 9.6to 11.2mm valve lift.

Also 12-13mm lift is generally reserved for high duration high overlap camshafts, which for the most part you can't run without piston cutouts.

^^^^^ What he said.
Your cam is not worn out.
Don't waste your money replacing the cam for another standard 400 cam.

[fausTVR]

Bobby Shaftoe said:

fausTVR said:

Forgive my ignorance here, but is 6-7mm deflection down to wear, I was expecting 12-13ish.

The rockers multiply the cam lift by a 1.6:1 ratio, so 6to7mm at the cam is 9.6to 11.2mm valve lift.

Also 12-13mm lift is generally reserved for high duration high overlap camshafts, which for the most part you can't run without piston cutouts.

Ah, I did wonder of the rockers multiplied it. Every day is a school day around here.

[LewG]

Bobby put that into words far better than I could! These were my thoughts going by that ratio it really isn't worn at all which is a pleasant surprise. Just a chassis clean up and the new clutch to put on and I'll be back to V8 fun again in no time

[QBee]

My last few daily drivers have all done around 200,000 miles on the original cam(s).
You have an under stressed Range Rover engine. Nothing to worry about.


Of course, your clutch is probably knackered. Mine was at 73,000......and the car was a 4 litre then.

[LewG]

That's impressive! I've had people claim 72k is high mileage but as you say it's proven parts, particularly that wonderful V8, all pulling around not a great deal of weight!
I have a clutch here for it, the old one was giving an incredibly heavy pedal and riding high so it's well due.

[J400GED]

LewG said:

That's impressive! I've had people claim 72k is high mileage but as you say it's proven parts, particularly that wonderful V8, all pulling around not a great deal of weight!
I have a clutch here for it, the old one was giving an incredibly heavy pedal and riding high so it's well due.

Before replacing the clutch, why not check for weeping at the rear of the master cylinder, along the shaft at the top of the clutch pedal and also check the slave cylinder is dry as well, then check the fluid level and bleed the system to see if that makes any difference?

It's a lot easier than replacing the clutch only to find a leaky clutch master/slave cylinder

[LewG]

It's okay the engine is out and on the bench haha. I will have a look at master and slave too to ensure all is well. The friction material still had life in it but the springs inside the friction plate were worryingly loose and rattling around so caught in good time I suspect. On a previous car I've owned I had a friction plate spring part company with the rest of it, wedge behind the pressure plate diaphragm spring and upon depressing the clutch snapped several of the spring 'fingers' and forced the release bearing round on the clutch fork. Not a pretty sight

[J400GED]

LewG said:

It's okay the engine is out and on the bench haha. I will have a look at master and slave too to ensure all is well. The friction material still had life in it but the springs inside the friction plate were worryingly loose and rattling around so caught in good time I suspect. On a previous car I've owned I had a friction plate spring part company with the rest of it, wedge behind the pressure plate diaphragm spring and upon depressing the clutch snapped several of the spring 'fingers' and forced the release bearing round on the clutch fork. Not a pretty sight

[carsy]

If the engine is out on the bench, its a quick job to replace the cam. I wouldnt dream of retaining the original cam or timing gear if its done 72K miles especially if the engine is already half undressed. If it aint gone yet it probably wont be far off.

[LewG]

Sorry perhaps I should've made myself more clear, this is where I'm at:

As you say it's a tempting prospect!