XJ12 Engine

Talk about the E-Type Series 3

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sideways60
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#1 XJ12 Engine

Post by sideways60 » Tue Oct 22, 2019 7:58 pm

Think ive got an XJ12 Engine ? , Can i tell Via the Engine Number ? , Value Aside does it really make a Difference ? ta Russ

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lowact
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#2 Re: XJ12 Engine

Post by lowact » Tue Oct 22, 2019 10:04 pm

From jag-lovers
SOHC V-12 Engines
7Sxxxxx 5.3 Liter E-type
7P1001 5.3 Liter XJ12/Daimler Double SIx Series 1 w/carburetters
7P4000 5.3 Liter XJ12 & D6 Series 2 w/carburetters
7P25001 5.3 Liter XJ12 & D6 Series 2 w/fuel injection
7P42300 5.3 Liter XJ12 Series 3 Pre-HE (suffix ? = 9:1, suffix HA = 10:1)
7P45001 5.3 Liter XJ12 Series 3 HE
8S1001 5.3 Liter XJS non-H.E.
8S18001 5.3 Liter XJS H.E.
? 6.0 Liter
Note that for V12s 1971 through 1979, LA and LB suffix was 7.8:1 CR and SA and SB suffix was 9:1 CR. For 1980, suffix HA was 10:1 CR. From 1981 ?? suffix was 11.5:1 CR and ?? suffix was 12.5:1 CR.
Regards,
ColinL
'72 OTS manual V12

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sideways60
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#3 Re: XJ12 Engine

Post by sideways60 » Wed Oct 23, 2019 5:58 am

7P76**LA , makes it a Low Compression [ 7:8 . 1 ] Series 3 XJ12 ? , Many Thanks Colin . Russ

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#4 Re: XJ12 Engine

Post by lowact » Wed Oct 23, 2019 11:53 am

I suspect not. Yr engine, 7P76**LA, would be much later than '79. Later than mine (7P55**HB) which is '86.
It is series 3 HE? HE engines, all the spark plugs angle inwards and are 16 mm. Pre-HE, the front 6 plugs angle forward, the rear 6 angle backwards and are 19 mm. High comp. is a defining characteristic of HE engines, US version was 11.5:1 (L suffix ??), Brit. was 12.5:1 (H suffix ??). Do a compression test, 200-240 psi equals 11.5:1.
Regards,
ColinL
'72 OTS manual V12

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#5 Re: XJ12 Engine

Post by sideways60 » Wed Oct 23, 2019 5:01 pm

Umm , its 6' up in the Air at the moment so i can't see the Plug angles , Appreciate ur Help , i'll be in touch , Thanks Russ

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#6 Re: XJ12 Engine

Post by sideways60 » Fri Nov 01, 2019 2:31 pm

Thanks Lowact ,

Its Back on the Ground and the front 6 point Forward and rear 6 point Backward ,

so ive got a 11.5 : 1 Pre HE , it is a Yank so your exactly Right , Many Thanks Russ

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#7 Re: XJ12 Engine

Post by lowact » Fri Nov 01, 2019 11:30 pm

Nah, if not HE is not 11.5. And if carburetors not S3 either? Engine number, are you sure that the 1st numeral after the P is a 7?. What car is it in? If E-type, what is the engine number on the plate on the firewall? One explanation, if for some reason the e-type block had to be replaced, and all the etype heads and stuff were moved over onto a new block. In which case, the new block’s engine number would not be a reliable indication of anything.
Regards,
ColinL
'72 OTS manual V12

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#8 Re: XJ12 Engine

Post by sideways60 » Tue Nov 05, 2019 7:03 pm

Sorry for the Delay Colin ,
My Carbs are SU's
What year did HE Start ? , [ my Plugs point forward and backward ] so its Pre HE ?
The Number on the Bulkhead is 7S64**SB ,
Its in a 72 S3 OTS
The Number on the Rear of the Block is 7P76**LA

I Ask all these questions because i need to Order Engine Parts soon and its the First Thing ur Asked For ,
Thanks Russ

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#9 Re: XJ12 Engine

Post by lowact » Thu Nov 07, 2019 1:30 am

I believe HE's first appeared in 1979.
It would be useful to understand why change was made, why the engine numbers don’t match?
You have preHE heads and, according to my interpretation of engine no’s, a HE engine block. Less issues if I were wrong about this.To double-check the engine block, compare with the following photo’s of where the engine no. is stamped on the block, HE does not have the reduced area between the number and the bellhousing.
Image
Image

if just the block was changed, it might be safer to use the engine number on the bulkhead when ordering parts. However more than just the block may have been swapped.

PreHE have flat heads and dished pistons. HE have dished heads and flat top pistons. I.e. pistons and heads must match. You can confirm this by compression test, using the following formula and round up the result to find yr compression ratio: CR > (cylinder pressure / barometric pressure)^0.9.

E.g.: Standard 5.3L V12 compression ratio’s are 7.8, 9, 10, 11.5, 12.5. Say u measure up to 156 psi cylinder pressure when testing at near sea level, where barometric pressure = 14.7 psi. (156/14.7)^0.9 = 8.38, therefore yr compression ratio is the next highest = 9:1. This is what you would want, the 2nd last letter of the engine number on the bulkhead is “S”, as previously this means that the original engine in yr car had 9:1 compression ratio.

Pistons and cylinders also need to match. Notice the last letter of the engine numbers, on your bulkhead it is B and onyour block it is A. This letter denotes the manufacturing tolerance/clearance between the pistons and the removable cylinders. These need to be matching, i.e. u shouldn’t use “B” pistons in “A” cylinders for example.
Regards,
ColinL
'72 OTS manual V12

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#10 Re: XJ12 Engine

Post by sideways60 » Thu Nov 07, 2019 7:23 pm

I Dont know why my Engine Has been Changed its an American Import ,
The Location and Type Face and Misaligned Stamping is Exactly the Same as ur 7P55 ,
It Runs Ok and Now ive Changed Every Bush , Rubber , Joint and Mounting and Steering Rack it Drives ok Too , i want to get ready for Spring
I'll Do a Compression TestOver the Weekend Colin ,
Ive Got a Bad Oil Leak from the Back of the Engine at the Moment , hoping its the Sump :fingerscrossed: ,
Many Thanks Russ

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#11 Re: XJ12 Engine

Post by lowact » Fri Nov 22, 2019 1:43 pm

Reason for the compression test, to confirm you haven't been lumped with HE (flat top) pistons under yr flat (preHE) heads. This would give you monster compression with lots of piston ring blow-by that would pressurise the crankcase and blow a lot of oil vapour out the rear crankshaft seal, this is a rope seal that is not vapour-tight by design. It would explain yr oil leak ...
Regards,
ColinL
'72 OTS manual V12

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#12 Re: XJ12 Engine

Post by sideways60 » Sun Nov 24, 2019 8:18 am

The Sump Came Off , new Gaskets O Rings , and its Still Leaking Like the Tori Canyon , so i Bit the Bullet and The Engine Out , Waiting to go to the Engine Builder , Rob Beere will do the Rear Main Mod , Who Knows whats Inside But it Will be Right When ive Finished , Im also Going Tremac too , Thanks for ur Knowledge Colin . Russ

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#13 Re: XJ12 Engine

Post by AussieEtype » Sun Nov 24, 2019 9:54 am

sideways60 wrote:
Sun Nov 24, 2019 8:18 am
Rob Beere will do the Rear Main Mod
What is the rear main mod for a V12? I know of a mod for the 6 but not heard of it for the V12.

Cheers

Garry
1971 Series 3 E-type OTS
1976 Series 2 XJ 12 Coupe

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#14 Re: XJ12 Engine

Post by sideways60 » Sun Nov 24, 2019 9:27 pm

The rear Flange that Holds the Flywheel is Machined so that a Modern Lipped Seal replaces the Old Rope one .

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#15 Re: XJ12 Engine

Post by lowact » Sun Nov 24, 2019 11:44 pm

sideways60 wrote:
Sun Nov 24, 2019 8:18 am
Im also Going Tremac too
T5 kit including new bellhousing?
Pre-HE and HE were designed for different transmissions, have different bell-housing bolt patterns, actually bolts align well enough, its the locating lugs that are different.
Currently u have a Pre-HE Jaguar 4 speed on the back of an HE engine block? There are 2 ways of doing this. The right was is to use a new, universal fit bell-housing. In which case u would already have the T5 bell housing. The wrong was is to rip out the lugs and just bolt it up, alignment cannot be reliable. New T5 kit including universal bell-housing would fix this.
Have u settled on OD ratio? Often 0.73 is recommended for V12E but if u tell them u r upgrading to 2.88 diff they may recommend 0.8.
Regards,
ColinL
'72 OTS manual V12

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#16 Re: XJ12 Engine

Post by AussieEtype » Mon Nov 25, 2019 3:19 am

sideways60 wrote:
Sun Nov 24, 2019 9:27 pm
The rear Flange that Holds the Flywheel is Machined so that a Modern Lipped Seal replaces the Old Rope one .
Oh Ok - thanks for that, as I said I was aware of it for the XK engine but not the V12. My rope seal does leak a bit and the engine is coming out soon so when out I might look at this mod as well.

Cheers

Garry
1971 Series 3 E-type OTS
1976 Series 2 XJ 12 Coupe

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#17 Re: XJ12 Engine

Post by sideways60 » Wed Nov 27, 2019 6:55 pm

Collecting the Full T5 Kit next week Colin , thanks for the Dowel Info , the Motor is sitting on the Floor so i can offer it on easily , The 2.88 is in and ive decided on the 0.8 5th , Brought the Rob Beere upgraded Oil Pump and PRV , just waiting to hear about the condition of the Liners and find out what pistons i Have before i go any further , He does a 9:1 Set thats Cheaper than OEM , got Fossways Starter and Alternator , and ordered a Set of Tubular Primarys as mine were US too , U feeling my Pain lol , ta Russ

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#18 Re: XJ12 Engine

Post by lowact » Thu Nov 28, 2019 2:57 am

Dirty one on the left is HE 12.5:1 flat top. Clean one on the right is XKE 9:1 (dished).
Subtle differences: rings at different height, skirts different shape, oil holes, etc.
Image
My OEM XKE 9:1 complete and matched pistons and liners have scrap metal value despite being in genuinely excellent condition. PM if interested. Freight would be brutal, excl. packaging is 42 kg.

What do u mean by "Tubular Primarys?"
Regards,
ColinL
'72 OTS manual V12

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#19 Re: XJ12 Engine

Post by sideways60 » Fri Nov 29, 2019 8:31 pm

Thanks Colin ur a wealth of Information , Hayward and Scott Exhaust , There not far from me Too and as my XJ12 ones were Bodged Together i Didn't really have a Choice , Russ

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