No problem. Does not really change anything. No 6 also suffers manifold issues. I still believe this to be a classic heat seize caused by lean running.

All this discussion really points out is reality vs. theory. So often the case in my chosen career.

 

The way I see it Jaguar had a lot of very clever people in their design team. They had years of development and testing in racing and production. They had a massive, in relative terms, budget to sort out the problems. What they came up with was a world beating engine that lasted over 40 in production. During that 40 years they further tweaked the design and made it better. They tried things like different heads. Different fuel management. Different gearboxes.Different blocks. Different materials. Different pistons. Different gas flows. Eventually they realised that no amount of money or design work was going to improve on the original XK engine design, improve on power, improve on economy and so they stopped production and designed another engine.

So anyone who comes along with an idea that with a limited budget, working by themselves in a single garage, a couple of nights a week, who can take a fuel injection system attach it to an XK engine to get more power and more economy has about the same chance of designing perpetual motion or cold fusion.

Want a better engine than the 2.4? Buy a 3.4 or a 3.8 or even a 4.2. Want an even fast better car than an original 3.8 Mk2 Jaguar go buy a modern car with all the electronics and sensors that come with modern cars but do not expect to work on it in a single garage late at night. When it goes in to limp mode take it to a garage where a parts swapper will plug it into a computer before he can tell you what is wrong, then give you a bill for £150 an hour labour,

Rant over.

 

Well, yes and no. Yes to the very clever people. We've had a lot of brilliant engineers in the UK and certainly in Jaguar. Though Jaguar engineering was more than a man in shed, it wasn't much more than a bunch of clever, enthusiastic men in a shed working on a very limited budget. That's why Jaguar survived when most of their UK competition disappeared through lack of cash. As such, aren't the latter day fiddlers and improvisers carrying on the Jaguar tradition?

 

Certainly Jaguar & Bill Heynes had one of the smallest engineering design teams on the planet and they were forever ludicrously busy. By modern comparison their design team was minuscule in XK engine & IRS design times. Flaws in the original XK design are not easily remedied. They should have listened to Weslake. Nevertheless the old girl did remarkably well for what it was.

 

Peter and Glyn I take on board what you have both said about the size of the design team but they still honed the development around the racing program and got as much as they could out of it. I wonder how many engines went in the bin having blown up under testing.To come along now and try to improve on the design by bolting on modern technology with just one engine to play with seems a bit silly, especially when it goes wrong with a piston melt down as Jagboi64 had. What next a super charger or a turbo?
I know we all like to have a fiddle in the garage trying to improve the performance but there is a limit as Jaguar found out so why do people think they are better than the original design team. No offence to someone who wishes to try but they would be better off using a modern engine rather than a 75 year old design, but don't put it in a Mk2 Jaguar body.

 

Flaws? For a 1940s design and recognizing that all engineering design is a compromise, the XK6 is pretty good, if not unmatched. How many other old, relatively mass produced engines are of the same standard or worth playing with today? And companies that should know better have produced several pieces rubbish since then.

 

My piston interference was machine shop error. Otherwise, why were 4 of the 6 pistons unmarked and the only two damaged? The reason was the skirt clearance was machined slightly too tight, in this case half a thousandth of an inch makes a difference.

I have actually considered forced induction, the XK's long stroke would be ideal for it. The engine was designed in a era when there was a tax advantage to having long stroke engines, and nothing to do any sort of engineering principal. For it's displacement, the valve size is smaller than ideal and forced induction could compensate for that. One thing against the XK though is the hemi is a poor combustion chamber design, for any given compression ratio it requires more octane than other designs. The swirl characteristics are also poor. It could ( and has) been redesigned using modern knowledge that wasn`t available to the original designers, an example is the forged pistons that Rob Beere makes that correct the swirl. Please don`t pretend that the design team in the 1940`s knew everything there was to know about engine design and the combustion process and no knowledge has been gained since then which can`t be retrofitted.

 

Second hand XK engines sell for £2k to £3k for something that needs to be completely rebuilt. Go down the scrap yard and take your pick of engines to fiddle with for £200 to £300. You could get a Nissan straight 6 for £1000 and do an awful lot more with it than an XK but I ask again please do not put it in a Mk2 Jaguar.

 

I've sometimes wondered if the long stroke arose from the machine tools that Sir William had available (without selling his soul to a bank). Remember the XK started its life as a 3 or 3.2 litre before they identified the need for more torque. Ron Beattie worked on some of the experimental 3 litres at the end of the 1950s. He later developed his own with the 2.4/2.8 litre block. He reckoned it was really the sweetest, most free reving of the whole family.

 

It certainly had flaws & Harry Weslake pointed them out at the time of design. Call them flaws or poor choices made. Either way I don't mind.

Then you had:

https://www.jagtas.org.au/torque/tec...-engine-block/

Fraser Mitchell has some interesting stats on this.

 

A couple of Issues with the Jenvey throttle bodies.:
Most EFI cars that are not direct injection have the injectors close to the intake valves for good throttle response. They are some distance upstream with the Jenvey depending upon the intake arrangement.
Programmable EFI generally works best from a MAP signal which is a problem for ITB's. You could combine each ITB MAP signal in a buffer to make an composite signal which again will impact throttle response or you could abandon the MAP input and use a throttle position sensor. The problem there is that at small throttle openings the TPI signal is extremely sensitive and the EFI tuning is difficult.

 

I understand and am keenly aware of the tax advantage issue for licensing. I'm quite happy to concede partial machine shop error. But consider lean heat seize to be part of the issue at standard piston to bore clearance if they got it right. Due to lack of accurate mixture distribution when tuned at the squeaky end you never seize all pistons. (see Peter's comments on "log" manifolds) ~ e.g. I checked all my piston to bore clearances & taper & ovality at my rebuild. They were exactly to OE spec & I have suffered zero issues with correctly rebuilt & tuned SU's. She runs like a dream. There should be no requirement to move away from factory spec on piston to bore clearance. I also Plastigauged all bearing clearances.

Of course engine sophistication, materials & design etc. have improved vastly since the XK was conceived. One should also concede that there was better British knowledge around from the likes of Weslake & others at the time as well. Even Alfa could have taught Heynes & Co a thing or two. The XK could have been even better than it turned out to be. To me the greatest thing about the XK is it's smooth torque characteristics from low RPM

Lyons also built these engines on pretty tired & antiquated equipment. It is well recognised that South African built engines were generally better than Browns Lane units because heads & blocks etc. were machined on new state of the art for the time equipment. Lyons got around our local content programme, which was by weight at the time, by doing a deal with our Govt. to send blank blocks, cranks & heads etc. to SA for machining & assembly for SA built CKD cars. (We built 2050 Mk2's here, 850 S Types & approx 800 420's. I have never seen a number of XJ6's but it was significant)

I don't want to upset anybody, but in the words of a certain British scribe who shall remain unnamed ~ and I grew up in just such a family. "British car buyers had an overwhelmingly patriotic orientation that to buy British was to buy better when [many] indications were to the contrary". (I have taken the liberty of softening slightly by the changing of one word.

Our family would not look at anything other than British vehicles until my mother broke the mould by buying a Chrysler Valiant followed by an Alfa likely due to my influence as I started my motoring life with a string of Alfas until company cars came along. She used to love jumping in my Alfas & reducing my rear tyre life.

Today our family are Mercedes & Toyota buyers. Both tolerate our harsh conditions well.

 

I just checked in, I'm surprised and delighted at how the discussion has developed. Fascinating.

I hadnt previously read much about inlet tract length, I know see the issue with the very short Jenvey ITB.

I get throttle body injection on the existing manifold has its issues.

When I said I like to get 30mpg on a long run, I was of course referring to imperial gallons, which I think is equivalent to 25mpg with USA gallons. I still think with a manual gearbox my goal could be in reach.

Interesting stuff.

 

Enjoy the project. If all we have really contributed is importance of length of inlet tract to ideal torque production we have helped.

Adhere to Jaguar piston to bore clearances or those recommended by the piston supplier. There is no reason to deviate from specification. I don't know if an engine rebuild is envisaged.

When it comes to initial system set up start at the rich end. Suggest 11 to 1 AF Ratio. Don't threaten the engine chasing fuel economy. You can fine tune as you go & once the unit is fully run in. Then you can start leaning the mixture in your quest but do it in small steps. Let us know how you go.

Watch engine temperature like a hawk initially. If it starts to rise abnormally ~ back off immediately.

Good luck!

 

A friend of mine has a 1970 4.2 E Type, all original. It was his great grandfathers car, who bought it new and been in the family ever since. He was doing a 4 year degree in automotive restoration, and as a project rebuilt the engine in the E Type. I sold him a set of NOS Hepolite pistons in standard size that'd guess were from the 70`s judging by the box. I'd had them for years and I didn't buy them factory fresh. He rebuilt the engine to factory specs and clearances and on his first drive all the pistons seized and looked just like the ones in the photos I posted earlier.

The car was running a set of SU's, so the AFR was unknown. However, he took the carbs off the engine previously, and it had run well for 70,000 miles on those carbs and he didn't touch the settings when putting them back on. The only reason he rebuilt the engine was it did have 70,000 miles on it, he needed a project for his fourth year class and he had access to all the machine shop facilities. The engine ran strong before, just was staring to use some oil.

So while I have no doubt you were able to get your S Type running well with factory clearances, I'm a bit gunshy of doing that after seeing two engine failures at factory clearances. I did talk to a machinist experienced with the XK engine afterwards and he said he always adds an extra half a thou to the skirt clearances and has not had any trouble with that.

 

Take a look at this article on variable inlet length vs dyno results. See how much the power and torque change, both in value and where the peaks are in the rev band simply by changing the inlet length: https://www.emeraldm3d.com/articles/...length-intake/

 

All I can say is that it is most unusual & unheard of in SA. But you are entitled to your opinion. My car was fitted with Genuine Jaguar Pistons (NOS) in their original green boxes. I have no idea who was manufacturing for Jaguar at that time. I think SA knows something about building XK engines. We built thousands of them for locally produced cars. Every machine shop here adheres to Jaguar factory specs for piston to bore clearance as did the local Jaguar factory in Blackheath & CDA before them in East London. Now the site of our local Mercedes Plant. They sadly demolished the old CDA plant that was a multibrand builder of cars that started in the late 1940's. Where my S Type was built. No 4 off of the local line. Jan 66. (I call it a 65 because it was somehow registered before it was built. Never been able to reconcile.)

 

Great example even on modern engines with other enhancements. Thanks.

Example of a variable intake manifold & swirl flaps on a 16 year old Mercedes M272 engine. V6 Quadcam. VVT et al. Just Pre Direct Injection. Port injected just behind the twin intake valves/cylinder. I have removed all the branding masks from the slides as this is a Jag forum & this is intended for illustrative purposes.

 

This may also be of interest. The engine is a Jaguar XK.

 

I should have mentioned that Figure 12 is the interesting bit for VE vs intake length as you might no want to wade through all the description.

I think the results have been smoothed. There's another version with more mention of Jaguar (I don't remember where) with almost the same lines as Figure 12, but with some small ripples, I guess due to some other resonance.