XK engine number identification!

[Phil5343]

Hi all,

I've been offered an XK engine, but its of unknown origin. It's an
early engine (pre XJ) looking at the casting and it has the
following numbers on it:

Block:

3 1/2 litre (this bit I can work out.. )
KJ5632-8

Cylinder Head:

R4682-9

Any help decoding the numbers would be of great help. My '68 Mk2 needs a heart transplant, and this might just be its saving.

Regards,

Phil

[lowdrag]

Mk2 3.4 so 1960 onwards

http://www.car-nection.com/jagbase/engines1.htm

Edit: seems have a different head since block indicates 8:1 compression and the head 9:1.

Edited by lowdrag on Friday 26th November 12:27

[Phil5343]

That sounds like it'll fit then! Is there any way of the head, i thought it wasnt original because of the compression number difference that you point out.

The head is the early type, with the screw in bolt style core plugs in between the plugs, and its painted red.

Im just trying to figure out if its worth buying!

Cheers,
Phil

[a8hex]

The R head should be from an E-Type so will be a straight port head. Mk2s normally have a B type head, although 240s and 340s had straight port ones. Does the engine come with the inlet manifold? B type and straight port heads need different inlets.

Red valleys indicate a C type head from an XK140, which would be a G series number.

[Phil5343]

The engine has no inlet or carbs, they were sold seperately, but i was told it had triple SU's on it. As well as R4682-9, which is stamped on the front of the engine near the timing chains, there is a flat block right at the back of the engine which has the number G170 on it.

Would i be right in assuming that this is a Mk2 3.4 block with a strait port C-type XK140 head then? And is that a good combination to have in my car? I have a set of triple 2" SU's to fit as well, so hopefully it'l be a good mix!

When you mention inlet manifolds, whats the difference? I have a manifold from a 420G, will that fit?

Cheers,
Phil

[jagracer]

Phil5343 said:

The engine has no inlet or carbs, they were sold seperately, but i was told it had triple SU's on it. As well as R4682-9, which is stamped on the front of the engine near the timing chains, there is a flat block right at the back of the engine which has the number G170 on it.

Would i be right in assuming that this is a Mk2 3.4 block with a strait port C-type XK140 head then? And is that a good combination to have in my car? I have a set of triple 2" SU's to fit as well, so hopefully it'l be a good mix!

When you mention inlet manifolds, whats the difference? I have a manifold from a 420G, will that fit?

Cheers,
Phil

You need to do some inner wing mods (and I think move some other stuff) to fit the triple SUs to a Mk2. You need to check the height that the carbs will sit at with the 420g manifold is the carb side is higher than other Jaguar-triple SU set-ups.

[jith]

Phil5343 said:

The engine has no inlet or carbs, they were sold seperately, but i was told it had triple SU's on it. As well as R4682-9, which is stamped on the front of the engine near the timing chains, there is a flat block right at the back of the engine which has the number G170 on it.

Would i be right in assuming that this is a Mk2 3.4 block with a strait port C-type XK140 head then? And is that a good combination to have in my car? I have a set of triple 2" SU's to fit as well, so hopefully it'l be a good mix!

When you mention inlet manifolds, whats the difference? I have a manifold from a 420G, will that fit?

Cheers,
Phil

The original red C-type head fitted to the XK 140 is NOT straight port Phil. Your E or 420 inlet manifolds will not fit.

By the way, the suffix 9, although it is stamped on the head, actually relates to the compression ratio dictated by the size of the dome on the piston crown, not the head.

Having said that , if you fit a green head from a 3.4 to a 3.8 block that would originally have a blue head, you will increase the compression, because there is a difference in the combustion chamber size, but the red heads were only fitted to 3.4 blocks from the factory, so they should have the same chamber as the standard green heads.

From memory, the difference between the green head and the red is the cam profile and the size of the inlet valves.

Edited by jith on Saturday 27th November 11:25

[richw_82]

jith said:

The original red C-type head fitted to the XK 140 is NOT straight port Phil. Your E or 420 inlet manifolds will not fit.

Why won't it fit? The exhaust ports are square/straight ports, the inlets are round ports. The inlet manifold has round ports at its mating surface. The stud spacing doesn't look to have changed.

Educate me please before we try something a bit daft and waste time!

If it turns out we can't use it, we've got a SIII XJ 4.2 head lying around amongst other bits.

Regards,

Rich

[jagracer]

richw_82 said:

If it turns out we can't use it, we've got a SIII XJ 4.2 head lying around amongst other bits.

Regards,

Rich

If you use the S3 head don't forget to blank off the two waterways at the back.

Edited by jagracer on Sunday 28th November 20:19

[richw_82]

Cheers mate! Already been warned about that one, but thanks anyway.

[a8hex]

richw_82 said:

jith said:

The original red C-type head fitted to the XK 140 is NOT straight port Phil. Your E or 420 inlet manifolds will not fit.

Why won't it fit? The exhaust ports are square/straight ports, the inlets are round ports. The inlet manifold has round ports at its mating surface. The stud spacing doesn't look to have changed.

Educate me please before we try something a bit daft and waste time!

If it turns out we can't use it, we've got a SIII XJ 4.2 head lying around amongst other bits.

Regards,

Rich

An original XK140 C type head would be numbered GXXXX/8 (normally 8, could be 7 8 or 9, the compression ratio).

This inlet port spacing is different to those used on the straight port head, the spacing is the reason a non straight port won't mate with a straight port inlet manifold.

The number at the front end of the valley on the vertical section is where the head number is usually found.

An R number would be from a 3.8L E-Type, which would explain the triple carbs. This is a straight port head.

The 3.8 and 4.2 heads differ in their water ways. The 3.8 inlet manifolds had 3 separate sections and a waterway that links them together. The 4.2 has extra waterways into the head so the whole inlet manifold is a single piece affair. The manifolds for the E-Type and the MkX/420G are different. The low bonnet of the E means the inlet manifold needs to drop the carbs down a bit whereas those from a MkX/420G the carbs are at the same height as the inlet ports.

Now I have no knowledge of fitting these to a Mk2.

On an XK150 then you can use the MkX/420G manifolds if you modify the inner wing to make space for the extra carb and you move the clutch fluid reservoir. You can't use the E-Types ones as they foul the steering column.

Mixing 3.8 and 4.2 parts is a matter of closing off water channels in either the head or the manifold depending on which way round you have it.

BTW, I've got a rebuilt Mk2 head sitting my garage I'd swap for either an E-Type or C-Type head.

[jith]

richw_82 said:

jith said:

The original red C-type head fitted to the XK 140 is NOT straight port Phil. Your E or 420 inlet manifolds will not fit.

Why won't it fit? The exhaust ports are square/straight ports, the inlets are round ports. The inlet manifold has round ports at its mating surface. The stud spacing doesn't look to have changed.

Educate me please before we try something a bit daft and waste time!

If it turns out we can't use it, we've got a SIII XJ 4.2 head lying around amongst other bits.

Regards,

Rich

As A8hex has explained, the inlet ports are differently spaced.

A further word of warning. The late S2s, early S3s were among the worst engines Jaguar ever produced in terms of quality control. They were seriously in the grip of the BL cutback scenario at that time.

I lost count of the number of warranty claims done on these engines. The two single most prevalent problems were the both the valve guides and the tappet guides working loose in the head. If you were lucky it would happen at very low speed, and the resultant clatter would alert the driver before serious damage occurred. At motorway speeds however, it was usually disastrous.

The obvious advantage with the S3 head is the much larger inlet valves, but if you are going to use one, I would replace all of the guides; at the correct tolerances!!

Edited by jith on Sunday 28th November 20:48

[richw_82]

Thanks guys, this was just the kind of info I was needing.

jith said:

A further word of warning. The late S2s, early S3s were among the worst engines Jaguar ever produced in terms of quality control. They were seriously in the grip of the BL cutback scenario at that time.

I lost count of the number of warranty claims done on these engines. The two single most prevalent problems were the both the valve guides and the tappet guides working loose in the head. If you were lucky it would happen at very low speed, and the resultant clatter would alert the driver before serious damage occurred. At motorway speeds however, it was usually disastrous.

The obvious advantage with the S3 head is the much larger inlet valves, but if you are going to use one, I would replace all of the guides; at the correct tolerances!!

I've had all the fun and games with early series 3 engines in the past. Cracked cylinder heads, cracks between bores in the block, and of course the tappet guides going walking and getting beaten into pieces by the cams.

The 4.2 head I have (that Phil might use) is a good one, prepared for one of my cars, but never used. It has the stake down kit and all the other work done. From memory, the valves on the series 3 are the same size as those on the D-type engine, although they're a different profile.

[a8hex]

If you want a well made SeriesIII head then you could look out for a J72 head. This is the military version. There are still NOS ones of these kicking round. I think SNG Barrat bought up a whole load last year (which is where my sump came from). The military engines were finished to a much higher standard.

[richw_82]

They had larger tappet guides and a stake down kit fitted as standard. The J72 was good in some areas and bad in others, crankshaft failures being common.

[Grantura2a]

Hello all,

I have a one owner 1951 Mark 7 sedan that has sat for 20 years. Many years ago, the head cracked, so we bought a replacement from a breakers. He said that it was a type c head. The number F2446-8 seems to point to a late 120. Anyone have any clue as to the value of the head?

Thanks,

Mike T