1850 Large Exhaust Valve Heads - Date?

[Edin Dundee]

Does anyone know roughly what date the larger exhaust valve heads were fitted to 1850s?

[Henk]

And an additional question from me: can anyone tell the difference in size?

[Jon Tilson]

Not totally certain but I always thought this coincided with the 75 revamp to single rail box, exhaust on the right and
dustbin style hub caps.

Jonners

[Edin Dundee]

And an additional question from me: can anyone tell the difference in size?

IMG_2612 by edindundee, on Flickr
Here's a photo of my head after skim and valve guide replacement if it helps.

Jonners, thanks, the head in the photo is the original from my car, which is a transition model just before HL.

[Toledo Man]

I've been looking through my early 1850 parts catalogue and there was a change of part number for the valves at engine number WF55000. This was presumably before the Dolomite range was rationalized in 1976 because all the 1850HLs used the same valves. My best guess would be around 1975 because the exhaust system was changed at commission number WF55000 I would imagine that roughly the same number of bodyshells and engines will have been manufactured during production. I know that having an 1850 with matching numbers in 1975 would be an impossibility but it should give us an idea of when the change occurred.

[Jon Tilson]

The numbers pretty much agree with what I said then.

The only real difference between a "transition" car and an 1850HL is the badges...

Jonners

[sprint95m]

The early 1850 head is based on the Stag LH head
(the slot under the cyl.3 & 4 ports is for coolant transfer through the inlet manifold on the Stag).

The later 1850(HL) head is based on the TR7 head.


By the mid seventies BL had decided to discontinue the slow selling Stag (although it soldiered on until 1977), the TR7 had been introduced
with a new version of the cylinder head (without the Stag's coolant slot),
so rather than have types of slant four 8 valve head in production, it made sense to adopt the new TR7 head for the 1850, which is what they did.




Ian.

[MIG Wielder]

I think the exhaust valves 155524 were the same throughout production. There was a change on the inlet valves from 145662 to UKC181 in "1976 " according to Rimmers catalogue. It looks like it co-incided with a change from a 4-gallery head water jacket to a 3-gallery water jacket. The rear-of-head plate changed at the same time, which may be another way of telling the larger valved head.
Tony.

[Toledo Man]

This is what my parts catalogues say:

Inlet valve
145662 to engine number WF55000 (which we reckon is somewhere in 1975)
UKC181 from engine number WF55001 (including the later 1850HL)

Exhaust valve
155524 for all 1850s