just out of curiosity will the supercharged heads and cams bolt onto th na block and if so wouldnt it improve performance? may be a dumb question but had to see if someone else ever considered it.

 

If you are refering to SC on 4.0l na then no. The SC doesn't have VVT and it also isn'to different mechanically.

 

Sorry to contradict Daim, but yes they do fit. No added performance. The heads are the same part number.
But the camshaft sensor reluctor(s) - 1 on an AJ26, 2 on an AJ27 need fitting if going from 26-27 or visa versa. The other thing is of course the VVT which will need fitting, the S/C cam 'flywheels' and timing chain sprockets are removed with 1 bolt.

 

hmm figured heads would fit with larger valve ports and that cams might be slightly larger. does anyone know if you can find performance cams for the aj26

 

Not that I know of....that would be a specialist job = expensive. Valves and ports the same on all heads.
Compression ratio obviously higher on the NA engine.

 

I know the heads would fit, I didn't state they wouldn't I only refered to the cams...

Maybe I should write totally mega ultra super duper clear about things...

 

thanks guys cleared that up quick so looks like im limited to actual machine work then. im sure I can work the heads over and improve performance shave a little here port and polish there maybe even bigger valves I really want to stick with the original engine. even if it costs more thanks again y'all

 

Sean I plan to do the reverse of jcreaden. I plan to put heads from a 99 AJ27 N/A engine to a 2000 AJ27 S/C engine. (Dropped valve seats on S/C engine). So the heads and cams are the same. All I need to do is remove the VVT from the intake cam and install the sprocket from the S/C head.

 

are there higher compression pistons available at least anyone know

 

The compression on the NA engine is already 10.75 to 1.
You will need racing fuel if you go with a higher compression. What are you trying to acheive? The most cost effective way to increase horsepower is to sell your car and get an XJR. That's the easiest way to pick up 98 more horsepower.

 

wow didnt realize it was up there already and im starting to agree with you about getting an xjr but that will have to be the next time around. thank you guys for the info. seems like jag squeezed everything they could outta this engine without forced induction. back to the drawing board then. thanks again y'all

 

I will post this AGAIN!!!!!!!!!!!!!!!!!!!!!!!!!!!!

All the TSBs I have (that no one reads) are in the large file area on this forum somewhere and on Gus's site.

Jaguar answered this 18 years ago.

Going 'the-other-way', you will need to PLUG the hole for using NA heads on SC engines.

bob

 

excuse me for not knowing how to navigate the forum that well just had a question didnt need the rude to go with the answer thank you for your input

 

Thanks for the info Bob. I didn't think about the oil supply for the VVT needing to be plugged. This is a future project and might not get to it for another year.

 

Yep. I carry out what Bob's TSB says...
Tap the gallery
Insert bolt, copper washer and a dab of threadloc
Done

 

80*

 

I was reading the ft lbs. I should use my glasses next time. Thanks for the clarification.

 

The cylinder head castings are the same and the port geometry is the same NA to SC.


You would lose performance however as you'd lose VVT.


The compression ratio is lower on the SC variant but that is attained through different dished pistons rather than flat tops