Capacity and compression ratio increase

[Curtis Bay]

Further to my earlier post, I have now removed all the emission control stuff from my US spec V12 and have tidied up all the unnecessary (in my opinion) vacuum pipes etc. I have obtained a vacuum advance unit and plan to fit that shortly but sadly the rear crank oil seal is leaking quite badly so my plans to use the car through the summer may be curtailed and my plans to rebuild the engine may be coming forward.

I would like to build the engine with and increased capacity (6.1 litres) and get a decent compression ratio at the same time.

Does anyone have any experience of the Rob Beere oversize pistons and liners or have any alternative suggestions?

Ultimately I will be looking to to go to full EFI with coil packs etc but for now it may be a bottom end rebuild with the original carbs and ignition.

[Woolfi]

"Ultimately I will be looking to to go to full EFI with coil packs etc but for now it may be a bottom end rebuild with the original carbs and ignition."
The 6,0L HE-Motor has more displacement with a longer hub. A longer hub produces a torque curve with the maximum at lower revs. Maybe the solution with the bigger pistons is not a good idea.
If you "open" the two silencers, plus two bigger inlet trumpets to the air-cleaner boxes plus 4 modified carb-needles, you will have roundabout 20 - 30 mor ponies and a better sound. This is a cheap und qucik&dirty solution for more fun with this car.
I don't believe, that the effort for a full EFI plus coil-packs is worth the effort. I hae compared times my car with 4 Strombies plus thge modification I described above with "efied" EV12. Both times the cars with the EFI had LESS torque in the range between 2000 and roundabout 4000 rpm. The kick in the back at 3000rpm with a carbed motor felt stronger than with the EFI-Cars. Maybe the two cars with EFI have not done well ?
Regards Wolfgang Gatza

[Curtis Bay]

Hello Woolfi

Thanks for the suggestions.

My bottom end rebuild is needed because of the failure of my rear crank seal and so whilst the engine is in bits I may as well address the other internal parts. My engine has the very low US compression ratio and to replace the pistons with high compression 5.3 litre versions is not significantly cheaper than increasing the size to 6.1 litres.

The fueling and ignition will be something I can play with once the block is back together but your suggestions would be easy to try and may be something I employ. However, the fuel efficiency and reliability of the EFI systems also appeals to me.

Has anyone built an engine with the oversize pistons?

[Ole-xke1974]

Assuming you have a manual car, one relatively cheap modification that will improve throttle response and potentially acceleration is the replace the heavy steel flywheel with the lighter version. Either a Fidanza aluminium flywheel or a lightened steel version.
Cheers ...... Ole

[Curtis Bay]

Thanks Ole

I have an auto at the moment but the gearbox will be changed for a 5 speed manual in due course. Since I have to find a flywheel it makes sense to fit an improved version. I suppose a lighter one will help so long as I don't go too light.

[Ole-xke1974]

Curtis,
we had a lengthy discussion on the Jag-Lovers forum about lightened flywheels about 1-2 years ago. The opinions were ranging from you can drive this smooth V12 without flywheel to a lightened flywheel will cause your car to stall easier.
I'v had my Fidanza for over a year and 11-1200 miles without any issues. If anything negative, it is that you can't just dump the clutch in idle - that will cause it to stall, but who does that any way ?
I do find the engine peppier and more responsive, but that's all butt dyno subjective data.
Cheers ...... Ole

[jagwit]

There are two other (inexpensive) options you may consider...

1) The 1980 XJS pre-HE 5.3 engine came with 10:1 CR. Scarce, but if you can find a good set of those;
2) Convert the engine to Euro spec HE with 12.5:1 CR. I did this on that E-type I EFI'ed, fitted the HE pistons and heads to it. It ran with a 4.2 XJR.

Having done a full EFI / coil pack conversion on my previous E-type, I am also of the opinion that unless you are after bragging rights, EFI does not hold much, over a well tune carby setup with vacuum advance on the dissy.

[Paul Buckley]

I have a V12 engine (from an XJ12 HE) which I bought in order to strip it of its EFI components.
Having done that the rest is for sale ..... block, pistons, crankshaft, heads etc..... if it would be of interest.

[Curtis Bay]

Hello Phillip, Paul

Thanks for the replies. Interesting about the 1980 Pre HE XJS pistons. Were they 1980 only? Also, could you run the HE pistons in an E-Type engine with E-Type heads but with a thicker head gasket to drop the CR a little or do the valves interfere with the top of the piston?

I am just kicking ideas around at the moment but the lack of new standard pistons with @ 9:1 / 10:1 compression ratio is frustrating. It does make me wonder what you do with a V12 E-Type with the higher compression ratio if you need new pistons.

For now I won't be buying a complete engine. I am already falling over V8's everywhere (another story)

Still hoping someone out there has installed the bigger Rob Beere pistons....Anyone?

[jagwit]

Were they 1980 only?

I'm not sure. I do know it was only the very last of the pre-HE's that had this 10:1 engine and it may only have been for the European market because of fuel quality. I'm really not sure of all this. Kirby's book might have more accurate info.

Also, could you run the HE pistons in an E-Type engine with E-Type heads but with a thicker head gasket to drop the CR a little or do the valves interfere with the top of the piston?

AFAIK it is not possible to run HE pistons with pre-HE heads. the CR will be in diesel territory and the valves (which are flush with the pre-HE "table top" heads) will interfere with the pistons.

I am just kicking ideas around at the moment but the lack of new standard pistons with @ 9:1 / 10:1 compression ratio is frustrating. It does make me wonder what you do with a V12 E-Type with the higher compression ratio if you need new pistons.

I recon going 12.5:1 HE would be, by far, the most economical solution by getting pistons and sleeves from a scrapped car (retain their positions!!! I believe the rearmost pistons differ internally from the rest). The only "downside" is that the HE heads don't really allow revving beyond 5500rpm. But the torque is "table top" all the way from 1000rpm to 5500rpm. Enough to make you smile.

[Curtis Bay]

Hi Phillip

Thanks for the info. It maybe the sensible option. Presumably I need the HE heads as well as the pistons and liners so maybe an XJS engine swap maybe easier.

Time to think.......

[jagwit]

"Presumably I need the HE heads as well as the pistons and liners so maybe an XJS engine swap maybe easier."

Correct.

It all comes down to whether you want to be able to claim a "matching numbers" car. I recon you could still claim "matching numbers" even if you install the complete (!!pre-HE!!) XJS engine, as long as you offer the matching numbers engine with the car when/if you sell. Its just not physically in the car.

Alternatively, build the HE pistons, sleeves and heads onto the E-type block and you also have a "matching numbers" car - strictly speaking. Could also save a whole lot of red tape by not having to change registration etc - if applicable.

!!pre-HE!!
Note, bell housing bolt pattern differs between pre-HE and HE!! This could have transmission implications....

[Curtis Bay]

Thanks for the warning about the bell housing stud pattern. I plan to fit a manual gearbox but I will need to make sure I obtain the correct bell housing.

[lowact]

I've no experience of the Rob Beer large diameter pistons, I've read that large dia, short stroke revs better but makes head dissipation less efficient. Perhaps if u want to be radical y'd fit the RB pistons to a long-stroke (6L) engine?

Instead I am preparing to upgrade to efi 5.3 HE 12.5:1 compression ratio, by fitting heads manifolds, pistons and sleeves to my e-type engine to keep matching no's and belhousing. One thing I am not fully on top of is exhaust manifolds, not sure if the e-type manifolds fit onto HE heads, e-type exhausts hug the block while HE pipes splay out?

Like Paul I 'purchased an HE engine (whole car actually) for the fuel injector bits, before concluding that the full HE upgrade (heads, sleeves, pistons) was the better sol'n, just the efi may not provide significant benefit over existing carb'd engine? Also hi-comp HE provides better performance and efficiency compared to even the 1980 10:1, the reason why the latter was so quickly superseded?

As I understand, the last letter of the engine no., "A" or "B" denotes the sleeve piston tolerances u don't mix them up. My e-type engine is "A" but my HE engine is "B" so my "matching no's will be sort of misleading in many ways ...

It's looking like I will using very little of the HE efi bits, cheaper and better to upgrade to a latest tech system, otherwise, as Phil points out, real benefit may be marginal. My ECU will be Adaptronic M6000, fully sequential fuel and ignition, Hi-Z injectors, custom fuel rail, distributorless (coil on plug). But not until i get back from UK brexit party, hope they don't cancel it ...

[jagwit]

not sure if the e-type manifolds fit onto HE heads, e-type exhausts hug the block while HE pipes splay out?

just the efi may not provide significant benefit over existing carb'd engine? Also hi-comp HE provides better performance and efficiency compared to even the 1980 10:1, the reason why the latter was so quickly superseded?

Colin, no problem fitting E-type manifolds to HE heads. The low and midrange torque of the HE engine is just fantastic. But you will BEG for an overdrive transmission then.

EFI bring refinement more than performance, like better hot and cold starting, better economy having more control of fuelling and timing. IF there is a performance gain, I recon it can mostly be ascribed to carb/ignition system not being optimally tuned. A sorted V12 EFI E-type is a lovely thing.

But I say again, if I had to choose AGAIN between EFI and an overdrive transmission, I would go for the transmission.

[lowact]

G'day Phil, thx for info re exhausts. Not choosing, doing both. I've an LdN overdrive ready to bolt on. Also thinking of changing the diff ratio, currently 3.54, to either 3.31 or 3.07, the latter would maybe make the OD too long? Do u still have the 3.31 that u swapped out? U bagged it mercillesly and i agree 3.31 and 3.54 only good for autos but, i wonder if it would be ok choice for manual with HE efi and OD?

[Dave123m]

Hi,

Whilst I've stored my original E-Type Engine, Auto Box & 3.07 Diff for when I either restore, sell or stop using the car for long summer road trips currently I'm currently running a late (1989) HE Engine from an XJS as it comes with the 'lip seal' rear crank seal (the Marelli Ignition Engine).

The engine runs full standard XJS EFI with an overdrive 4 Speed Manual Gearbox with Fidanza Aluminium Flywheel & the 2.88 XJS HE Differential, for my 3000 mile road trip to Sicily last year it ran faultlessly & effortlessly, even at altitude in the heat of Mt Etna

IF you chose to use the XJS HE engine the exhaust manifolds do indeed fit without issue however the biggest challenge (with the late engine) is Jaguar didn't drill & tap the large blank on the front cover on the late engines so you can't directly transfer the Oil Filter pipe which is essential when putting the XJS HE Engine into the E-Type as you will need to transfer the oil filter & sump from your current E-Type Engine

Thankfully Jaguar still cast the blank boss so with the assistance of my toolmaker father was able to drill & tap the front casting without removing it (which would have required heads off) so I was able to convert the engine without the need to rebuild it.

As mentioned previously the rear transmission face of the block does indeed have dowels / holes in different locations which prevents direct fitment of the original gearbox however these are easily relocated & re-drilled (on the XJS Engine) where required so the bellhousing doesn't have to be bespoke.

The beauty of the above conversion is whilst it sounds dramatic I haven't had to modify a single panel or drill any additional holes so can revert to original at any time I choose without any trace of the current conversions remaining.

Happy to share detail of the conversion as I did this myself so should be able to remember most of it.







Best of luck with whatever you decide.

Dave.

[Whitact]

For anyone wanting an easy way to fit a later V12 to their S3 there is a kit available that would allow the original engine to be retained complete.
https://www.rushtonengineering.co.uk/v1 ... to-e-type/
No connection to these guys, they just happen to be local.
Cheers,

[Curtis Bay]

Thanks for the heads up on using an HE engine. Does the same apply to the 6.0 litre HE? Also, if I can find a late 6.0 HE engine with 4 speed auto is that worth fitting as a single unit?

Beginning to wonder if a 6.0 HE with carbs may be the way to go with a Rushton Engineering conversion or my home made adption and use of my E-type bits. Any thoughts?

[Dave123m]

Hi,

Happy to be corrected but I looked at the 6.0 4 speed Auto gearbox however I think it's controlled either by it's own ECU or via the Engine ECU so fitting could be more onerous, plus they are reasonably hard to find?

If fitting an XJS Engine you will also need to consider the Thermostat Housings where they connect from the heads to the radiator, you will need either different rubber pipes or I transferred my original E Type Thermostat Housings.

If transferring the original E Type you will need modified metal connecting water pipes (above the exhaust manifolds) as currently they warm the Carb inlet manifold, you will also need to fit a Water Temperature Sender if planning to use the EFI (the boss is already on the E Type Housing but it will need drilling & tapping).

If fitting EFI the Air Filter modification is very minor & is to the RH front only (to clear the bonnet) everything else fits & the original XJS air filters can be retained.

With regard to Carbs vs EFI unless you are particular about the appearance of the engine personally I would use the HE engine exactly as Jaguar intended with the EFI, it's more efficient, easier to start (hot & cold) & once fitted rarely needs maintenance.

Unless restoring I would never change back to Carbs, after all I believe the original E-Type engine was planned to have EFI & the Carburettor arrangement is not the worlds greatest design!

Good luck & regards,

Dave.