I am looking for a bit of performance improvement for my pre HE engine. Does anyone here has tips for suitable pistons and camshaft replacement?

Team CJ forged piston set has been my favourite so far (forged, 9:1 compression ratio). Does anyone has first-hand experience with these?

As for the camshaft, I understood durations over 270° were not very good outside of race track.

 

Any performance improvement in the V12 will cost $$. Just replacing pistons will gain very little, you will need revs to gain power all NA V12's making over 400hp spin to 7000rpm+ and 500hp needs 7500rpm and 6.0L to do it without TWR like budget.

Are you running the Lucas ECU or aftermarket?

First area to improve is intake manifold the OEM ones are not good for making power, plenums are too small. You can cut the plenum off and weld on a 4" square aluminium section and move TB's to the front.

 

 

warrjon: I am using Holley carbs, so no ECU. And the OEM intake manifold is indeed fairly restricting. I installed a new one, designed and optimized for direct airflow. please see the photos - top: OEM version, bottom: new intake manifolds. And you are right, I do not expect huge improvements just by the pistons. But the lighter pistons should allow for higher rpms there and there. Just for the feeling. Since Cobra is lighter than the original XJS, the engine already feels quite potent. It is easy to get into troubles - which is part of the fun! 500hp would be my death...

Alan Lindsay: It is very different. I love V8 sounds, but the V12 screaming can be pretty addictive. And scary.

 

 

Myself and a friend went to England in 1987 or 88 and bought a Dax kit. John Tojeiro was still alive then and we got to meet him at the Dax shop. They had a demo car with a Jag v12 and it ran great , very fast. We got a kit and chassis that was set up for the v12. I installed a 427 Chevy L88 engine. It was a beast. You didn't say if your car is a manual trans or automatic but if its a manual a lightweight alloy flywheel would make a drastic difference in performance. When I worked for Group 44 our engines had Arias pistons in either 11 or 12.5 to 1 compression and Crane cams .with the flat heads.

 

Very neat engine bay you have there.

If I were you I would go fuel injection, getting more power from a V12 with a Holley set is in uncharted territory.

Megasquirt has been done a lot on the V12 and all later model manifolds will bolt straight on.

 

I use CRANE Cams , custom designed by Crane ,from Grp44 lobe/timing, for street use , have had NO wear after 25yrs, new springs shimmed! nice sound at idle, and run out 6500/6800rpm no problem, cant float the valves anyway!

my pistons factory 9-1 , slight modify for 9.2-1, large bowl in piston top, Pre HE!

lightweight convertor and flex plate,(quick revs).

 

JBL Specialty: The car has a manual transmission. And the lightweight alloy flywheel is a good tip. I definitively intend to do this - to lower the "inertia" of the engine.
Arias Pistons do not have pistons for Jaguar V12 in stock. I suppose you used a custom design? Anyway, compression ratio 11+ would be probably too much for my application.

warrjon: The Holley carbs allow for a good setting in multiple regimes (with an A / F analyzer). And I wanted to go into the uncharted territory - it's part of the fun for me. For example the manifolds are custom made and even CFD-optimized (with respect to the flow), using ANSYS CFX. . It should be relatively easy to get the engine close to the 400 hp mark, even without increasing the volume. (Better intake and carbs, polishing the inner surfaces etc.) This should be more than enough for me to handle.

ronbros: Compression ratio 9.2:1, bowl in piston top - that is exactly what I would like to do.
What were the timinng on your cams? I could not find the Grp44 lobe/timing.

 

to be honest i have no idea what Crane did to the factory cams , regrind only allows just so much, but they did NITRIDE the finished product!

they did reshape lobe ,it can be seen by eye ,putting side by side, more area under the curve envelope, lift came to .410 thou. at .005 lash, but it was a little to radical so they recommended increase lash clearence
to .010 seems now perfect now, 25yrs and counting , had the cam covers off a while back , all looks good NO wear. and makes a nice solid lifter sound at idle,(i like it).

when i picked up the cams from crane , they gave me a floppy disc with all the specs on it, lift rate in minutes not degrees, back then i had no idea what i was looking at anyway!
also finding some one with a floppy reader computer!

and to make things more stupid , i lost the disc in the moving from Florida to Texas , and many other small stuff,,DUH!

quick change of subject, when my shop was in Florida, i had some nice cars to take care of, one was a genuine AC cobra with the 427 Ford Aluminum block, twin 4 barrells, and YES it was a beast to drive ,but you could really show off in the parking lots!

 

also couple things i did for my engine , aware of the overheat potential of Jag V12s , i had the exhaust port ,ported and Ceramic coated ,to keep heat flowing thru, and not fully reaching coolant !

also Ceramic coated the complete head surface, again not letting to much heat of combustion reaching the coolant!

i had talked with LANKY from Grp44, and when they where doing there engines , that coating was not available, but he thought it would be a great mod!

most of there engine failures were connected to overheating, head gaskets , O-rings, Cooper seals,ETC.
the one that hurt the most was around 1985/86, when leading Daytona 24 hr, the last hour started lossing coolant and slowed losing the race!! AAUUGH.

as we say those were the days, i still have my 1978 Jaguar roadster , modified V12 , but dont drive it much, its an over my head beast, so its up for sale.

one of there last races(44), was hauler truck came by my shop,Daytona), and opened it up to show the XJR-5 car,1987.