1850 Cylinder Head skim

[Magenta Auto Sprint]

I picked up a spare head for my 1850 Auto sometime last year. The guy bought it as a spare for his stag until he was told it wouldn't be suitable.
it has been sat around for many years.

I finally dismantled it and have taken it in for a minimal skim. today the machine shop says that the skim will come very close to the inlet valve seats and the head may have been skimmed before.

I know that the sprint head has an approximate dimension of 120.5mm I was interested to know if a similar dimension existed for the 1850 head.

Malcolm

[soe8m]

In one of my posts start of another new project you can see a high milage head that was skimmed to the seat. It doesn't matter when the skim is just touching the seat. When it's for more compression what really benefits an 1850 you can skim the head on an angle to have a smaller chamber.

Jeroen

[DOLOMITE 135]

Sprint heads are measured between the face and the base of the cam journal I think?
I have roughly measured my NOS (early) head in the same manner, and the measurement came out about 112.6mm.

[new to this]

You can buy head savers for the stag ( stainless steel gasket) to go between the head gasket and the head one of them mite fit the dolomite

Dave

[tony g]

I think the 120.5 measurement comes from the cam cover gasket face to the head gasket face. (on a sprint)

Tony

Sprint heads are measured between the face and the base of the cam journal I think?
I have roughly measured my NOS (early) head in the same manner, and the measurement came out about 112.6mm.

[xvivalve]

No, it’s cam journal Tony, the cam gasket to head gasket dimension tapers!

[MIG Wielder]

Sprint heads are measured between the face and the base of the cam journal I think?
I have roughly measured my NOS (early) head in the same manner, and the measurement came out about 112.6mm.

That looks like a good measurement. I have an 1850 head here on loan and also measuring from the rear cam journal to the face of the block by the rear cover lower bolt hole with a Mitutoyo set of callipers I get 112.81 mm.
So since your head is NOS it looks like this one has never been skimmed !
Goody !
Tony.

[Magenta Auto Sprint]

Excellant, many thanks to everyone for their replies.

I'll ask the machine shop to measure the head to see if it has been skimmed before.

I have also found the head saver gasket, it is 0.5mm thick and needs to be bonded to the head with silicone sealant. I am guessing that this is done just before the head is fitted. it costs about £40.

malcolm

[xvivalve]

As I understand it, the measurement was a factory minimum dimension; most therefore would have been in excess of that dimension.

[Magenta Auto Sprint]

I spoke to a very help guy at Gosnays Ltd who make the head saver shim, they make three thicknesses; 20, 40 & 60 thou shims. he also mentioned that Tony Hart Racing, LDParts and James paddock also make a thicker head gasket for the Stag, gaskets can be bought individually as well.

so more options should I need them

Malcolm

[soe8m]

Stag shims and gaskets etc don't fit a 1850 head.

Jeroen

[tony g]

Yes of course lol

Tony

No, it’s cam journal Tony, the cam gasket to head gasket dimension tapers!

[Magenta Auto Sprint]

My cylinder head has returned from the machine shop (Head Line Mk Milton Keynes) £38 +VAT.

I am not sure if this is an 1850 head or a TR7 head, perhaps somebody could advise?

The 1850 head in the Haynes manual seems to show a 3 - 4mm step from the gasket face to the valves and this head doesn't have that but it may be a later design as it has the larger valves.

If it is a TR7 head will it fit the 1850 or are there piston cutout issues, compression problems etc?

Many thanks

Malcolm

[xvivalve]

Jeroen posted pics of the various heads in a thread a while ago...

[DOLOMITE 135]

Previous thread on 1850 heads here:
http://forum.triumphdolomite.co.uk/vie ... 4&t=32449