Pre-he pistons in an he
#21
11-21-2015, 07:21 PM
Veteran Member
We have several reliable unmodified utilitarian vehicles. I'm looking for an interesting project car.
Seems better to know what can and can't be done before buying it.
For example, knowing what can realistically done to the 5.3 to increase displacement, it may make more sense to buy with a blown engine or an sbc transplant and plan for sourcing a 6.0. Or, if an engine were to come available, it might make sense to buy it first, rebuild/modify it, and then find a car to put it in later.
Or I may just say to heck with it and plan on keeping the 5.3 basically stock and just drive it as it came from the factory.
Seems better to know what can and can't be done before buying it.
For example, knowing what can realistically done to the 5.3 to increase displacement, it may make more sense to buy with a blown engine or an sbc transplant and plan for sourcing a 6.0. Or, if an engine were to come available, it might make sense to buy it first, rebuild/modify it, and then find a car to put it in later.
Or I may just say to heck with it and plan on keeping the 5.3 basically stock and just drive it as it came from the factory.
This is a good strategy, modifying a Jag V12 for serious power is not a cheap exercise.
There are basically 4 iterations of the V12 block.
Early BW transmission
TH400 transmission
Rear main seal modifications
Jaguar 6.0L modified for 4L80e trans
The 5.3L can be modified for around 350-380hp, a 6.0L with same mods around 400-450hp.
Port intake manifolds
Smooth intake ports, see pic although this is my 6.0L head
Port and de-burr exhaust manifolds
Aftermarket ECU
Cold air intake
free flow exhaust.
Its the torque that matters. The Marelli 5.3 makes more torque lower than the pre-HE mine is rated at 450nm around 3000rpm with 90% available from 2000rpm. The 6.0L is 480nm, (mind you this is in Australian/European spec).
All 5.3L cranks are forged as are Marelli 6.0L, later 6.0L cranks are cast I believe these started when Ford added EDIS ignition to the V12.
Rods are the same for all V12 iterations and are forged. There is a company in Europe that modify Chev rods (narrowed) to suite the V12, this requires the 2.3"crank BE journal to be ground down to 2.1"
My car is stock (5.3L) apart from an exhaust and 3.54 diff, and is as quick as my mates (LS1) 285kw HSV to 100km/h, its almost line ball, because my car makes torque much lower and I am out of the blocks so much quicker, he does not start to real me in until we reach about 70km/h.
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ronbros (11-22-2015)
#23
11-22-2015, 07:51 PM
Veteran Member
I haven't posted my intentions on a thread here, but I am in the process of putting a Whipple 3.3L SC on the 6.0 I got for my 89 convertible. As with a lot of projects, it has kind of "morphed". I originally was going to install the 6.0 from a 94 XJ12, then I found a triple disc clutch set up on eBay. (ripped 3 clutches out of a 71 XKEV12 I had). Then I noticed how the LS series engines GM is supercharging. And well, here I am.
I say all of this to say that lowering the compression on a HE engine isn't nearly as hard as you might think. After consulting with a couple of guys who've "been there done that" rather than talk about it, here is what I've come up with. The 94 6.0 had a steel crank. ALL rods are forged. The Jaguar rods are massive compared to American muscle. The pistons? The domes are NOT flat. The ones in my engine are concave. By .012 in the center. The domes are .289 thick at their thinnest point. Some of the custom forged pistons are less than .100. A Jag V12 has full floating piston pins with circlips. The top ring land is 5mm. From those who have run these engines, one was taken to 16:1 compression ratio with longer rods, ran at 8000 rpm, and still lives on to this day. I did the math. It only takes a .080 gasket to get my 11:1 compression down to 9.25:1. I plan on rounding off all of the edges of the combustion chambers in the heads, CC'g them, and maybe get 9:1. Maybe even a little less. I've already purchased the Electromotive TEC3r to manage it all.
I'm not wealthy guys. I'm more or less a back yard builder that is patient. I look for bargains. But I spend where I have to. If you love the V12, stop talking about it except to tell us what you've learned from what you've done. Pass along information. But by all means, have fun!!
I say all of this to say that lowering the compression on a HE engine isn't nearly as hard as you might think. After consulting with a couple of guys who've "been there done that" rather than talk about it, here is what I've come up with. The 94 6.0 had a steel crank. ALL rods are forged. The Jaguar rods are massive compared to American muscle. The pistons? The domes are NOT flat. The ones in my engine are concave. By .012 in the center. The domes are .289 thick at their thinnest point. Some of the custom forged pistons are less than .100. A Jag V12 has full floating piston pins with circlips. The top ring land is 5mm. From those who have run these engines, one was taken to 16:1 compression ratio with longer rods, ran at 8000 rpm, and still lives on to this day. I did the math. It only takes a .080 gasket to get my 11:1 compression down to 9.25:1. I plan on rounding off all of the edges of the combustion chambers in the heads, CC'g them, and maybe get 9:1. Maybe even a little less. I've already purchased the Electromotive TEC3r to manage it all.
I'm not wealthy guys. I'm more or less a back yard builder that is patient. I look for bargains. But I spend where I have to. If you love the V12, stop talking about it except to tell us what you've learned from what you've done. Pass along information. But by all means, have fun!!
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ronbros (11-24-2015)
#24
11-22-2015, 10:56 PM
Only correct if talking about the 6 litre. XJRS. The initial 5.3 litre versions were the same basic motor as the XJ12.
Last edited by baxtor; 11-22-2015 at 10:59 PM.
#25
11-24-2015, 05:22 PM
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I haven't posted my intentions on a thread here, but I am in the process of putting a Whipple 3.3L SC on the 6.0 I got for my 89 convertible. As with a lot of projects, it has kind of "morphed". I originally was going to install the 6.0 from a 94 XJ12, then I found a triple disc clutch set up on eBay. (ripped 3 clutches out of a 71 XKEV12 I had). Then I noticed how the LS series engines GM is supercharging. And well, here I am.
I say all of this to say that lowering the compression on a HE engine isn't nearly as hard as you might think. After consulting with a couple of guys who've "been there done that" rather than talk about it, here is what I've come up with. The 94 6.0 had a steel crank. ALL rods are forged. The Jaguar rods are massive compared to American muscle. The pistons? The domes are NOT flat. The ones in my engine are concave. By .012 in the center. The domes are .289 thick at their thinnest point. Some of the custom forged pistons are less than .100. A Jag V12 has full floating piston pins with circlips. The top ring land is 5mm. From those who have run these engines, one was taken to 16:1 compression ratio with longer rods, ran at 8000 rpm, and still lives on to this day. I did the math. It only takes a .080 gasket to get my 11:1 compression down to 9.25:1. I plan on rounding off all of the edges of the combustion chambers in the heads, CC'g them, and maybe get 9:1. Maybe even a little less. I've already purchased the Electromotive TEC3r to manage it all.
I'm not wealthy guys. I'm more or less a back yard builder that is patient. I look for bargains. But I spend where I have to. If you love the V12, stop talking about it except to tell us what you've learned from what you've done. Pass along information. But by all means, have fun!!
I say all of this to say that lowering the compression on a HE engine isn't nearly as hard as you might think. After consulting with a couple of guys who've "been there done that" rather than talk about it, here is what I've come up with. The 94 6.0 had a steel crank. ALL rods are forged. The Jaguar rods are massive compared to American muscle. The pistons? The domes are NOT flat. The ones in my engine are concave. By .012 in the center. The domes are .289 thick at their thinnest point. Some of the custom forged pistons are less than .100. A Jag V12 has full floating piston pins with circlips. The top ring land is 5mm. From those who have run these engines, one was taken to 16:1 compression ratio with longer rods, ran at 8000 rpm, and still lives on to this day. I did the math. It only takes a .080 gasket to get my 11:1 compression down to 9.25:1. I plan on rounding off all of the edges of the combustion chambers in the heads, CC'g them, and maybe get 9:1. Maybe even a little less. I've already purchased the Electromotive TEC3r to manage it all.
I'm not wealthy guys. I'm more or less a back yard builder that is patient. I look for bargains. But I spend where I have to. If you love the V12, stop talking about it except to tell us what you've learned from what you've done. Pass along information. But by all means, have fun!!
XJS cruising along.
#26
11-24-2015, 07:22 PM
Veteran Member
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