The MKVI Saloon continued

Hi guys,

I received an email from Patrick Coombs the other day relating to information stored on the old site about the MKVI:

http://jag-lovers.org/saloons/prc/xkengine.html

"This vehicle really did exist and my Father was the 3rd owner after George Hack, in Bristol.

My father was an ex RAF regiment soldier and did a lot of voluntary service at Filton Aerodrome that was still partly a military base. There he met George Hack, who coincidentally was about to sell the jaguar. My Dad used his military pension to buy it and owned it for about 2 years, before selling it on to the owner of a string of butcher shops, who operated out of Thornbury. After that, I was not able to trace any further history, until I received a phone call in the middle of the night from a very excited American guy, who wanted to know everything there was to know about the car.

I realised the other day when I was looking at it again, that the thread I had found was on your old website, so I thought I would contact you and give you a photo of the car!!

Tony Otelo owned back in 1999, does anyone know where it is today?"

Hi Nick,

I have seen other photos of it, possibly here on JagLovers. The radiator was moved forward and a longer bonnet fitted unlike the odd MkIV that has had an XK engine fitted by cutting into the scuttle.It appears in Allan Crouch’s book on pages 131-133.

Peter

Hello Peter,

Do you know if it was fitted with a gearbox from the XK120? That would have given it quite an apreciable top speed.

Tim

Hi Tim,

Reading Allan’s text HRW488 (not JVC 441) was tested and gave:
0-60 16 sec, 0-70 23.3 sec, Standing Quarter 20 sec, Top speed 90 mph although the car had not quite reached its maximum. The XK engine was of 3442 cc but gave 160 bhp. The MkVII with the same power reached 100mph and this was put down to the “much more efficient body design”.

Peter

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The last I heard 623053 (JVC 441) is still in the hands of Tony Otolo near Boston in Massachusetts USA. This is the one that William Lyons drove regularly.

The other one 620004 (HRW 488) was the factory test mule and was broken up by the factory, not sold, presumably not saleable due to numerous mule modifications.

The registration HRW 488 was transferred to another car 623173. It is not clear whether this last one had an XK engine or a standard pushrod engine, or both (reports vary). It has not been located, presumed lost.

The SH/JH gearbox is exactly the same for Mark V and XK120 (up to '52), no difference in ratios there, but certainly different rear axle ratios could have been tried in the test mule.

Okay, now you’ve peaked my interest Rob. What was the axle ratio in the 120 compared to the MKV?

Trust you are well?

Tim

Yes, keeping busy here with car restoration, and I’m the facilities engineer at my church, which means I install emergency lights and big screen projectors, repair holes in walls and fix leaky plumbing and fix the lawn mowing tractor and any other broken stuff.

With the ENV axle in the XK120, 5 ratios were offered: 3.27, 3.64 (standard in 120), 3.92, 4.30 (standard in Mark V) and 4.56. AFAIK any of these could be put in a Mark V with an ENV.

With the Salisbury type 2HA axle there were 3 ratios: 3.77 (standard in 120), 4.09 and 4.27 (standard in Mark V), and again any of these could go in a Mark V with Salisbury 2HA.

Later on the 120 got the type 4HA (as did the Mark VII) which offered 6 ratios: 2.93, 3.31, 3.54 (standard in 120), 3.77, 4.09 and 4.27 (standard in Mark VII).

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Hi Rob,

Good to know you are okay and busy.

How would installing a 3.92 ratio in a MKV with an ENV diff affect the performance of the car?

Tim

Hi Tim,

It would give 8% higher speed in each gear and reduce acceleration a bit. In top gear that is if the engine has enough HP to overcome the rolling and wind redistance.

So 8% to 90 mph would result in 97 mph.

Cheers!

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Hi Tim,

As Pekka points out, you need the horsepower and so to achieve maximum top speed you need to arrange for the peak power to correspond. If you have too high a gearing then wind resistance will prevent you from even getting up your to your engine’s peak.

Many years ago I plotted the power and speed graphs for our cars here. You can probably assume the drag factor of the MkV is similar to the SS Saloon as the actual top speeds from the road tests are very similar.

Peter

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Hi Peter,

Yes, very informative and most likely very true. So the 125 bhp achieved by the 3 1/2 Litre (I would say easily with good fuel and the right advance) should be good for 90+ mph in a Saloon (and DHC) and the claimed 100mph in the SS100. The XK120 with ca 160 bhp could easily top the claimed 120mph, I recall a standard XK120 in Finland in the 1950’s on our terrible roads was recorded to exceed 200km/h (125mph).

Once and if I get it all sorted out and get my “running in” completed on the MKV DHC I will take her to a dyno just out of curiosity AND to be able to adjust the AFR to something reasonable under load, so I will know I am not running lean at 100-120km/h

I did the same for both my E-types before driving through Europe as I would hate to blow a hole in a piston on the German Autobahn at 200km/h+! (125 mph+)

FWIW I never got to test how fast they would go. I sold the Series 1 4.2L 2+2 that showed (100% stock) 228 HP (DIN) at the dyno and the best I got was slightly above 220km/h (137 mph), but that was with three passengers and luggage back in 2002. That was with the O/D engaged just above 4.200 rpm and a 3.31 final drive.

Three years ago when we were coming back from Europe (via Denmark and Sweden) with my at the time 15 year old son, we hit 229km/h (142 mph) on the GPS near Celle in Germany in the evening when suddenly there was no traffic. The problem was that we were very soon at our exit from the Autobahn to our hotel. :smiley:

That was with the 1972 Euro spec, 100% standard V12 OTS #1S20183 at the time still with it’s original OPUS ignition etc. Final drive 3.54. IIRC in 2015 the dyno showed 233.1 HP (DIN) @5.375 rpm on the second run (35 deg overall advance) and the factory stated 272 HP (DIN) @5.850 rpm so I was missing a few ponies, maybe they could be found with careful tuning. :wink: (376Nm @ 3.710 rpm)
(US Spec was officially 250 HP (DIN) @ 6.000 rpm.)

That’s an unrestored car and not-rebuilt engine in any way, with just a bit over 100.000kms on the dial. Top up of course, very noisy above 5.000rpm in top gear, but not as much engine noise IMO as with the XK engine.

The MKV / MKIV engine is fine IMO until 4.000rpm, but unlike with the V12 I don’t feel comfortable taking it higher. Maybe I should think about changing the final drive (diff) some day if the dyno numbers look good! :smiley: It’s not my car’s original rear axle anyways, when I bought the car it had the rear axle and rear brakes from a Ford Fairlane or something and therefore the spare wheel well (and the fuel tank inside it! :open_mouth: ) had been “reformed” with a sledge hammer! :hushed:

It would be interesting to find out what had been done to that one MKIV DHC that allowed it to achieve the 140+ mph on the salt flat. :wink:

Cheers!

Ps. Also really good to know that if we want to take a Saloon to 150mph, we need about 500 HP! :laughing: :+1:

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Hello Peter,

Thank you very much for all that wonderful information. I was merely interested in what might happen with the different ‘diff’ ratios? I am not likely to make such changes as it’s expensive and very time consuming. I’d much rather explore adding an overdrive to the drivetrain as a few people seem to have done, successfully. Putting the car on a dynamometer might be an interesting exercise to determine and set optimum timing and mixture for the car.

Tim

My SS wasn’t very happy above 4000 rpm either but after balancing the engine it’s much happier now that it isn’t wasting its energy trying to shake itself apart.

I don’t know the story of the MkIV on the salt. Do you have a link?

Peter

Hi Tim,

You might also like another bit of comparison fun here.

Peter

Hi,

Here it is:

And sorry, I remembered a few things wrong.

  1. It wasn’t in Nevada, but in Lompoc, California, I guess some sort of speed trials.
    (There are air bases nearby, those where the places were a lot of races took place in the 1940’s and 1950’s)

  2. It wasn’t 140mph, but only 117.5 mph (on May 9th 1949) which is FAST for a pushrod DHC. Almost 190km/h and that was back in 1949, almost exactly 72 years ago.

That car (# 637196 / #SL3208) was registered just as my MKV DHC (#647194 / #Z2453)) with the engine number and not the chassis number which seems to have been the normal procedure in CA up to the early / mid-fifties.

Cheers!

Hmmm! If I believe in my power/speed chart it would need at least 220 bhp. Perhaps there was 30 mph tail wind that day.

Peter :thinking:

Hi,

I think it may be more that they removed the headlamps and the windshield and used some kind of tonneau cover over the passenger area, like we were guessing five years ago in that discussion.

Also removing the side panels from engine bay would reduce engine bay air resistance and like we can see in many pics form the old speed trials, taping over door gaps etc can also help reduce drag quite a bit and smooth hubcaps like @Wiggles on his Jee-type. :wink:

Cheers!

Hi,

That reminded me that the last time we flew back home form Florida, the Finnair flight had a 300+ mph tail wind, we had a ground speed of over 1380km/h = over 850 mph. The flight crew was really excited as they made a record and MIA → HEL in less than seven hours when it normally could take about ten hours.

Cheers!

Full Moons, baby!

Probably will jump the Jeep’s top speed to ludicrous…:stuck_out_tongue::stuck_out_tongue_closed_eyes::stuck_out_tongue_winking_eye:

So you are thinking from Snail to caterpillar?

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