Valve Shims

Its cheaper to have the valves ends done. You can have the shims ground - they hold them on a magnetic chuck and surface grind.

Whats caused the need for thinner shims? have the valves sunk into the seats? Unleaded petrol, in a leaded engine?

If its the SAAB also Triumph and think Marina for shims. There is still a limited size range.

r

...but this would require the head to be removed?

It actually needs thicker shims than it's got but still slimmer than the available range.

I suspect the valve seats have been over cut at some point in its 45 year life and 'homemade' undersize shims have been fitted as a result.

I believe XK heads are ok on unleaded and the valves don't seem to have receded as the tappet gaps haven't closed up - quite the opposite, hence the need for new shims. It's a healthy engine, good compression and it returns 24mpg (good for an S type!).

From my research the SAAB shims are available in the sizes I require but I need to confirm the diameter - does anyone know the diameter of the Triumph (which model?) or Marina ones?

You need to check that diameter which I don't recognise. As far as I'm aware most of the old Imperial engines like the Jag, Lotus, Imp etc used 5/8" (15.875mm, 0.625") diameter shims. Aftermarket suppliers then made these as

15.55mm diameter shims to allow them to also fit other engines including the Saab 99 and 900, Maestro and Montego 1.7 and 2.0, and Rover 2.3, 2.6 engines.

The Saab ones are available down to 1.77mm. However if yours really are

17.5mm diameter these would very loose in the valve cap, not that this would actually stop them functioning.

Shims can be ground thinner within certain limits. They are generally case hardened with a case thickness of about 10 to 15 thou which you don't want to grind right through. That means you can take about 5 thou a side off.

0.25mm total.

Your other two options are shortening the valve tip which is fine as all OE valves are through hardened right down to below the collet grooves and using lash cap shims which fit over the top of the valve stem and don't use the valve cap for location purposes.

or if you are a real animal you can take a little grinder and grind the end of the valve in situ. I saw this several times in the early days of the Suzuki GS engine which had shims. Even worse is that the owners claimed it had been done by a motorcycle shop.

If you need them ground, we have several precision surface grinders with mag chucks in our toolroom at work. Drop me an email if you want them done. cheers, JB

jmbyrne_AT_greenyonder.co.uk (changing colour to BLUE obviously).

The Triumph Dolomite ones available are 090" to 114" can't find my bucket full or I would have measured the diameter. (Saab is the same motor)

What you have to watch is the the edges, some have square edges whilst others ( I thing marina???) have rounded edges. The round edge type tend to sometimes jump out of the cap.

Your cheapest way is the measure what your requirements are then have them ground.

I would measure the clearance - remove them - measure the shim - and see if you can swap any around.

then have the rest modified to suit. or source new ones.

BTW have you asked at a JAG place if they have any to swap at a charge?

r

"sweller" gurgled happily, sounding much like they were saying:

The "B-engine" in earlier 99s was developed from the Dolomite lump - but heavily so in all bar the very earliest 99s - and by the time the 900 had come along it was even more heavily so.

sweller said the following on 03/04/2010 16:11:

Hi,

A bit late ... I found the sims from my 8v 900 heads + spares bought at the time.

Measuring the diameter of a couple (with calipers not micrometer), I get

15.6 and 15.65mm.

I remember me grinding them with my fingers (and my fingers too) on emery paper till they got to the right thickness. Anyhoo, they lasted another 8 years in the car (sold by then) when the flies took the body-work away.

Charles

Cheers JB - local engine recon place sourced and ground some XK shims for me. For the same price as the usual suppliers ?3 ea.

Put it all back together today - look out for posts on how to straighten bent valves....

I couldn't find any of these in the UK - could you point me in the right direction - thanks!

XK engines have larger shims but the general view is the smaller dia ones will be ok.

I managed to source and have ground, cheaply, XK shims - which was handy.