Oh no ... valve and rocker damage

[Chris71]

Just when I thought the light was beginning to appear at the end of the tunnel ... Top end issues.

My dad's been reassembling the engine (unlike me he's a professional engineer with hands on experience of engine building) and earlier today he noticed some marking on the top of one of the valve stems.

As well as the damage to the valve, it turned out the hardened section of the associated rocker was completely gone. On closer inspection, another one of the rockers on the other side had deteriorated too. The rest appear to be okay.

Is this a common fault?

The engine suffered a major crankshaft failure, but it's hard to see how that would have had an impact on the head. Camshaft is more or less okay and there's no sign of damage to the pushrods.

We've got a couple of new valves on the way and obviously something will have to be done about the damaged rockers, but I'm pondering whether to replace the whole set as a precaution.

[BeastMaster]

Chris - the loss of the steel pad on the rocker is a common problem which allows the valve stem to drill into the soft aluminium of the rocker. This then allows the valve timing and lift to be lost and then the ticking sound as the lifter can no longer cope with the large increase in gap.

I have replaced a couple of rockers on mine, one which was missing and two which were cracked but without any valve stem damage. Two options for replacement are available, the standard LR aluminium with steel pad or a aftermarket all steel rocker.

I decided to keep LR original and inspect the rockers each service for signs of cracks on the steel pads. I was put off replacing with aftermarket parts as a production batch were in ciculation with out of tolerence oilways which was causing low oil pressure, besides which the cost of replacement ran into a few hundred pounds which seemed a little extreme when my problem could be solved at around forty pounds.

Andy

[spend]

Classic symptoms Chris... Just putting new rocker arms in is plain silly IMHO, shafts tend to get wear + ovals, valve stems turned into grinders... It is really just the effects you have to expect running tuned camshafts ~ they are working the valve train harder so you can't really expect the longevity of the std set up (which is fairly marginal to start with).

I tend to buy new valves, but I suppose you could get the stem tips refaced. The guides do seem to be fairly durable, and my mate Pete has an idiom that if guides & seats have stuck in place for so long why risk changing them - and he even makes his own guides If you mushroom the valve stem don't screw the guide ID removing it would be my concern.

One thing that always bothered me is the push-rods. I have never seen an engine without evidence of push-rod scoring, yet when turned over & checked they have reasonable clearance? I can only deduce that either the rods are bending/flexing or popping out of the cups, yet can't believe that the latter would result in anything but serious damage.

[Chris71]

Ah. Well, that's sort of comforting, I guess!

We've already got new valves on the way for the two which were damaged. So maybe the answer is just a couple of Land Rover aluminium rockers to go with them and regular inspections?

[spend]

If your dads methodically checking under a magnifying glass , I'd also ask him to have a careful look at the wear patterns on the rocker shafts & spring seats.

I've seen a lot of spring seats bashed into enough to seize the spring & cant it in use, which can't be good. Cutting them down and inserting replaceable shims always seems such an easy solution to future proof against wear.

If your rocker shafts are worn then you get into the trying to find a matched set of rockers & shafts... Remember oil fills the shafts & pressure is maintained by the fit of the arms and shafts... (potentially weaker on the right hand bank where the mains are solely fed from BTW?)

Funnily enough folks seem to be continually obsessed with lifter pre-load as an excuse for all these 'challenges'

[BeastMaster]

Chris - Spend mentioned it above, but thought I would say it again - be very carefull removing the old valves, it is so easy to damage the guide especially when the stems have issues - Andy

[Chris71]

BeastMaster said:

Chris - Spend mentioned it above, but thought I would say it again - be very carefull removing the old valves, it is so easy to damage the guide especially when the stems have issues - Andy

Thanks gents, noted.

[Chris71]

Here's the damage to the rockers:


And the resulting damage to the valves:

[Goaty Bill]

Chris71 said:

Here's the damage to the rockers:

And the resulting damage to the valves:

Dead

[Comadis]

"The engine suffered a major crankshaft failure, but it's hard to see how that would have had an impact on the head."

only as an idea:

was the bottom end failure a result of the top-end wear? (metal particles in the oil)

[spend]

I'd say you've been running for a while to get that top end damage, and the crank failure would have dead stopped any running at all.

There is precious little clearance for crank/bigend against the crank case, look for evidence of the miscreant rocker pad getting wedged v crankcase if you are trying to make a relationship between the two faults? ie fash will result in bearing failures, shrapnel jamming freedom of rotation might just be enough mechanical shock to snap crank?

[Comadis]

i had it once with a ford engine, a follower was wearing (due to hardening problems from manufacturing), 3 days later the oilpressure dropped a bit and the (new)oilpump was found to be worn and another 3 days later the engine went bang with a bottom end damage....all caused be the metal-particles from the worn follower.

[Chris71]

Possible I guess. Oh well, the oil pump etc. is now being stripped as well to make sure there's nothing lurking in there any longer.

Thank God I went in with a contingency fund.

[frenchie TVR]

Chris,

Good luck with the rest of teh rebuild ... there is light at the end of the tunel!

Frenchie

[Chris71]

frenchie TVR said:

Chris,

Good luck with the rest of teh rebuild ... there is light at the end of the tunel!

Frenchie

Cheers Frenchie. Although one might argue that by now there's damp winter weather, salted roads and the reality of sub-20mph again at the end of this particular tunnel.

I'm determined to do a thorough job on the rebuild, but I won't have the contingency fund for another after this, so not sure how much longer I'll be able to keep it once it's on the road. I don't want to be in the position where I couldn't cover a second mishap.