So, I have been slowly gathering parts for an engine build for my XKR and in a stroke of dumb luck I was able to get my hands on an Aston Martin Vantage 4.7l crank in really great shape at STEAL of a price (don't ask how much you will just hate me!). It spun one rod bearing but looks like it can be polished out. That is a beautiful forged piece, fully counter balanced with a hair more stroke (.7mm) than the jag 4.2. I am planning to bore the block slightly so I need to have custom pistons made and no sense in having a forged engine and using the factory con rods so I am going to have rods made as well. I'll take pics once I actually start the build for the curious among us.

Quick question for those that have gone before me, what is a safe bore for a 4.2 that will be running 20+ psi of boost at ~9.2:1 compression? I was going to do a .5mm over just to get everything true and round but if the block can go 88 or 89 safely and still leave enough meat on the liner walls to be strong enough for boost then what the heck. Also I am trying to find a manufacturer that can make the rods and pistons in house, not a ton of places in the states do both. I spoke to a place in Europe that will do a full set for $3500 (3200 euros), just not sure if that is a good price.

Here is the plan so far
4.2L block bored to *86.5mm
Aston 91 mm forged crank
Factory crank bearings
TBD on rod bearings (if the crank needs to be ground I will have the rods made to fit a different bearing that offers oversized sizes)
Forged rods
forged pistons
4.0L XKR heads (going into a 2000 and I don't want to have to change my intercooler set-up)
Head stud kit
Bedplate studs (for the larger M10 bolts)

Any advice/suggestions are welcome!

 

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I can't help you but I will be watching eagerly and cheering from the sidelines.

How are you planning to make the 20 psi of boost? Are you going with a twin-screw supercharger (lookup threads by Avos, who made a twin-screw Kenne-Bell kit making 650 wHP), or are you going to go with turbos?

 

I already have the twin-screw kit from Avos on the car. That is making about 21# right now....thus the need to strengthen the motor or lower boost to a safer level....guess which route I am going!

 

That will be an insane Jag. I think you will end up having the most powerful XKR yet. How much power does it make now, and how much do you plan to make with the engine upgrades? Do you also have a water-meth injection kit? I feel like I am going to live vicariously through you as you go through this adventure. Please post lots of pictures throughout the process and provide dyno charts and videos when you've got it finished.

What other modifications have you done or are you planning? Standalone ECU? Manual transmission swap? Limited slip differential? Bigger brakes?

 

Get an insurance quote before you start

 

The 4.2L Block can be bored to 88mm as was done in the AJ41 (4.4L). However, I don't think that engine was boosted? The best advice is to research AJ41 boost mods for reliability and cooling etc..

Found this thread: https://www.jaguarforums.com/forum/x...ssible-145255/