Exhaust valves again.

[djm16]

I had the head off the 3-litre for I hope the last time for a very long while. This was to replace the inlet valves and guides that had been b**gered up by another machine shop.

While I had the head off, I checked the exhaust valves for pitting (moderately heavy) and when I had cut back the pitting I was left with valve heads that were getting a little on the thin side, so I thought I had better replace them.

I ordered a set of new exhaust valves from Wadhams. Disappointingly, they are way out of spec, with the shafts being 3 thou smaller than the correct .343".

I have been here before, so perhaps it was a little naive to expect things to be different this time round, but in my defence the last time I bought a new exhaust valve (it was also way out of spec, so I didn't use it) it was for a P4 90, which uses a different valve.

Anyway, here is the email I have sent to Wadhams:

Dear Admin,

This order relates to a set of six 3-litre exhaust valves. They arrived here safely, but I am disappointed that they are considerably out of spec. The shaft dia should be .343 inches, it is instead .340 inches. This means that the new valves flop around in the valve guides to an unacceptable degree.

Is there any reason they have been machined like this?
Even allowing for the slightly higher coefficient of expansion of SS(304) for example, the valve would have to get to 2,000 degrees before it even reached a comparable clearance to a standard Rover original exhaust valve.

Regards
David

To be clear, I am not having a go at Wadhams, as I appreciate the service they provide to help us keep our cars on the road. I will post their response.

[djm16]

1) There was no reply from Wadhams. So I now have a set of new exhaust valves. They might be useable with new guides (not mine) so I will hang on to them. The other possibility is finding a set of guides for another vehicle that have .340 (+1) bores and fitting them.

2) Here are some pictures that explain why I needed to replace the existing exhaust valves. The top pictures shows clearly that the material of the mating surface is welded to the base metal of the valve. Excessive trimming of the valve has worn through to the base metal (see the colour change). The lower picture shows the base metal eroded away from under the harder mating surface, leaving it prone to chipping.

[djm16]

I am fortunate in that I live quite close to a friend who stockpiled used 3-litre parts, and when I told him about my valves, came over with three buckets of used exhaust valves (around 200 of them). Around half could be discarded immediately on the grounds of excess corrosion or wear, the rest I cleaned roughly and sorted by shaft diameter. The aim was to find a set of 6 that when put in my guides would still be in spec.

Two valves as they came out the bucket.

100 valves sorted by shaft dia, least wear on the L, and all the valves with more than a thou of wear put into a box elsewhere.

Attachment Deleted

For reference, the best valves had a shaft dia of 8.692mm (my micrometer is metric) which is 0.3422". The new valves from Wadhams are 0.340 or 8.636. Even the most worn valves in the discard bucket were more than 8.636 dia.

When I was done, I had several sets of useable valves, some of which I was able to pass on to another enthusiast restoring a LandRover 6c engine, plus a complete set for my P4.

Thank you P*** G*******.

[enigmas]

Why not simply use "Bronze K Liners" with your new exhaust valves from Wadhams?


Bronze K Liners

From the above link.
Below, a sample of sizes from an extensive list of "bronze valve guide liners."

Part No. Imperial size
KL1958ST 11/32 x 2.250 ID .343
KL1959ST 11/32 x 2.400 ID .343
KL1923ST 11/32 x 2.500 ID .343
KL1841ST 11/32 x 3.125 ID .343

[MK IA Norway Viking]

I have an MK IA engine with excessive noise from the valve train. I have renewed the cam, all cam followers, rocker shafts (all four of them), new bushes for the rockers. The valves are not original nor are the seats - many years ago I fitted hardened seats and valves from Roverpart London because of the disappearance of leaded petrol. I still have those valves and seats in the cylinder head. The noise is subdued when I put synthetic lead in the petrol. Any suggestions on how I can make my engine smooth and civilised ?

[Phil Nottingham]

All the Rover seats and valves were unleaded compatible - later replacements were not so good at one point.  The valve guides did wear and if seats are replaced the guides and valves must bereplaced as well

[djm16]

Hi Vince, thanks for the suggestion, but I was not going to pull the engine out again. It is possible to fit new guides with the engine in the car, but K-liners would be a problem. In any case, a .343 K-liner with a .340 valve stem is still 2 thou more play than Rover spec.

Re noisy engine quietened with lead substitute, sounds like your ignition may be a tad advanced, given that petrol additives cannot get to any part of the valve train except the valve heads. I suppose it is the valve train making the noise and not a small exhaust leak?

[enigmas]

Hi David, there is a link to the K liners in my post above.
Click on the blue "K Liner" term if wanting to peruse what is available.

Perhaps the sizes below are better suited to your needs. If not then disregard this post.

PART No. Imperial Size

KL1961ST 11/32 x 2.500 ID .339
KL1983ST 11/32 x 2.400 ID .341

[djm16]

Actually, thats a very good suggestion, thanks Vince.

But I sincerely hope I never have to replace the exhaust valves again!