Hello All.

Was at a garage today & they had an XK140 FHC being restored. Having a quick glance at the engine block next to the car, noticed it had "3 1/2 Litre" embossed on the side! Took a closer look & it definately said "3 1/2 Litre" (the half written as a fraction, not ".5").
Just out of curiosity, did Jaguar make a 3.5 Ltr XK engine???

 

in the 1940's the Jaguar MK-4 had a 3.5 litre engine, but not the XK engine twin cam as we know it.

 

Ah yes!
Now I think of it, the cylinder head was quite narrow & tall. Central channel between the cam-shafts was only just wide enough for the row of spark plugs.
Thanks.

 

The Jaguar Mark 4 saloon and also the Mark V had the Standard Motor Co. 3.5 litre pushrod engine or the smaller 2.5 litre fitted. There was also a 1.7 litre 4-cylinder as well, up to 1948. Jaguar purchased the production machinery for the Standard engines after WW2, before that they were supplied by Standard. The XK engine started off as a 3.4, then came the 2.4, 3.8 and finally the 4.2. The XK was double overhead cam, of course, not pushrod, and very advanced for its year, as side valve engines were still in widespread use.

 

Early Jaguar "3.4" XK engines had 3 1/2 LITRE cast into the block. Actual Capacity 3442 cc.







XK140

 

😍😍😍

 

The blocks were cast by Leyland Motors up near Preston.

 

As Glyn stated the 3.4 was actually 3442cc .
The 3.8 was 3781cc.
The 2.4 was 2483cc
The 4.2 was 4235cc
It appears the rounded the figures up or down to the nearest point and then stamped that into the side of the block.

Question though when you rebore your engine from standard to +30, +60 or +90 thou pistons how much more CCs are you getting. Does anyone have the mathematical skills or access to a guide that would tell you what CC you now had. I had my 3.4 bored out to +90 and have always wondered what CC I now have?

 

Are you sure that's right, I've never heard (in any engine) a piston of no more then 40 thou over size ?

I suppose one could go to a jobber and request what ever one wants, but 40 thou is usually the max, if the engine is that worn, sleeving the bore is usually required.

 

Quick calcs suggest:

Cylinders bored out 20 thou = 3.48 Ltrs
Cylinders bored out 30 thou = 3.50 Ltrs
Cylinders bored out 40 thou = 3.53 Ltrs
Cylinders bored out 50 thou = 3.56 Ltrs
Cylinders bored out 90 thou = 3.63 Ltrs

(Assumes:
Nominal Stroke = 106 mm
Nominal Bore = 83mm,
Nominal Capacity = 3441 cc)

 

Thank you Cav very informative.

Yep +90 Jeff as it said it on the box and who am I to argue. I don't lie about these things you know just state the facts.

 

The 3.4 engine has tons of meat to rebore to +90 thou. You can't rebore a 3.8 to that extent. The 4.2 is a different block with siamesed bores & a narrower centre main bearing.

 

I would assume Glyn that you could bore a 3.4 out to a 3.8. The stoke is the same on both engines its just a question on how much metal is in the bore to remove.

 

The 3.8 is a 3.4 block with liners fitted. Jaguar found that there was not enough metal for just a straight bore-out, so fitted sleel liners to spread the load out more.

 

If you fit liners. Been done quite often. As Fraser mentions 3.8's have always had liners.

 

To amplify Frazer's point.

All production 3.8 XK engines came from the factory with cylinder liners made from Brivadium, an alloy developed by Bristol for its sleeve valve aircraft engines. It is one of their best features.

Maximum rebore permitted + 30 thou after which new liners should be fitted.

 

This is my 1968 340 engine I’ve rebuilt it also has 3 1/2 litre on the block.