www.jec.org.uk

There was a series of different engine block blues used to denote the compression ratio on the 3.8L series available for Mks VII, VIIM, VIII, and IX. Unless my memories playing tricks AFAICR

Did this blue colour scheming also apply to Daimler Sovereign 4.2L? I believe my 4.2L was a mid-80s version, but have no idea what its compression ratio is (was) The engine number is 7A35393-8 (8 = 8:1?). Heritage could only confirm that it was an 80's Sovereign

Thanks to anyone with clearer memory and or some lists to refer to

Mid eighties 4.2 litre cars had a standard compression ratio of 8.7:1. Earlier XJ numbering nomenclature was to add a suffix (L = low & S = standard) to the engine number to indicate the ratio. Hence, being unsure when that arrangement ceased, I wonder whether your last digit is an S and not an 8. Mike.

After several log-in attempts I've finally managed to get to reply

Thanks for the reply
This is what's stamped on the block -- but could this be the cylinder head number?
[URL=http://s1361.photobucket.com/user/ ... jpeg[/img][/url]

Here's a pic of what my 4.2L looks like now...
[URL=http://s1361.photobucket.com/user/ ... .jpg[/img][/url]

Since the lump is coming out, might as well get the colour correct before it goes back

That looks like an engine number. Early emission versions (USA etc) of the fuel injected 6 cylinder engine did use an 8:1 compression ratio. I would have expected a standard UK car to carry a "9" after the engine number since the stamped numbers were always rounded to the nearest whole number. Could the engine have been replaced? Does the log book engine number match the photo? Could the engine have been changed? Or, could the car have been destined originally for a non UK existence? Mike.

Mike...

This lump is in a Mk IX -- I was told by Heritage it was ex-Daimler Sovereign of the 80s but they couldn't tell me anymore
Yes that number is not on the V5C although that does show engine capacity as 4200, number shown is Z4268.
Not an engine numbering series I know about. But heck, what do I know?

Now I better understand the issue, a little! From what I recall, the engine block should have 4.2 on the casting which should settle its capacity. The engine number isn't an XJ series 1 or 2 number so looks to be later although of similar nomenclature. It also occurs to me that Daimler DS420 saloons of the eighties continued with carburettors and a low compression ratio. Hence, my best guess is that is what you have. Mike.

Well done every one, I dare not pursue this topic further but there are still unanswered questions.
Mike , you will have to appear on Master Mind, And your specialist subject is Jaguar engine colouring and numbering !

Aha! That makes sense.
When Heritage said Daimler Sovereign I automatically jumped to thinking XJ6 series,
not the 420
Not good as that puts the lump back to 1966/69 manufacture
283bhp without ancillaries and an 8:1 compression ratio.

I'd better get my Gunton out

Thanks due to all who scratched their brains

Think Daimler limousine which continued production through the eighties and the low compression engine (7.5:1, rounded to 8 after the engine number), still on carbs, makes sense for a low volume machine designed to waft gently. BHP wasn't important so less than 200bhp was perfectly adequate for the task. To go back to the original query on engine colours, I think you will find that Jaguar abandoned colour coding when it started employing accountants (with suitable apologies to any such qualified readers, including one of my daughters!). Mike.

Thanks again for all the replies. Doesn't look as if (from the photos I've got) that this 420 range Daimler Sovereign 4.2L cylinder head's been blue colour coded. Unlike the 3.8L lump in my previous '59MY Mk IX.

So I'll just do the outside of the block in Hammerlite black -- does it matter which one or is there something specific in Hammerlite's range I should use?

Accountants are useful, especially in Belize, etc.

Richard ,
I have used Hammerite smooth, tin and aerosol which works and looks OK