I HAVE A 2003 STR THAT IS ALL STOCK, other then putting a bigger supercharger pulley on it(which I plan to do) what do you recommend to increase the horsepower? cams?and whatever suggestions you have can you give me vendor information where to buy from...thanks

 

You don't mention the mileage on the car, but since it's 12 years old i'm going to guess >100'000mi or close to it.

If I were to be doing it all again;

New cats 200cell, new upstream O2 sensors
Full service; new plugs, filters, coolant, new thermostat, probably even a carbon-clean
Smaller top pulley, bigger bottom pulley
Intake tube aka Caldoofy, K&N filter, remove the WOT flap from the airbox
Then think about water/meth injection

With higher mileage, you really need to get the engine running as strong as possible before you start trying to add power, think of it as regaining lost power first.

 

its at 98000 miles

 

what kind of a hp increase do you think them mods will get me....I own my repair shop and have a couple techs that work for me so the labor will be free

 

As was said, try to regain the HP from the stock engine first. I installed a intake from Caldoofy with K&N filter. Very nice work, chrome and reasonable price. I think he is still doing them. He in UK but timely and reliable. Know that a aftermarket intake enhances the supercharger whine, which I love. I also did exhaust. I noticed an increase in power mostly on the low end.

 

If the car has only ever been serviced "by the book" then it'll still have it's original spark plugs in it...

https://www.jaguarforums.com/forum/s...sel-faq-67634/

So first off look at covering the major service, plus some extra items, like the thermostat, possibly the water pump, do the cats and O2 sensors as well (the cats will likely be choked) and also think about the transmission & diff fluids.

Depends on how much power it's making now. Stick it on a dyno & see.

Most of the STR guys who've done all those mods are looking at 350-360rwhp

A dead stock car with clogged cats might struggle to make 300rwhp

 

so no one is doing engine mods ...cams? I want to get in the high 400's in hp...

 

High 400's at the wheels means you need a twin-screw, you'll never get that power with the eaton blower.

Mine will be going to the dyno next week after resolving some issues and just getting new cats fitted, should also be getting a tune and i'm hopeful of high 300's in rwhp.

Will let you know.

Regarding cams there has been only a couple of custom cam-grinds done, Avos in Belgium had a custom grind. You should get in touch with him.

https://www.jaguarforums.com/forum/p...xtra-hp-42059/

 

You would want a smaller supercharger pulley, not a larger one. There is a very limited aftermarket for these cars; you will need spray or a twin screw to reach the kind of power goals you wish to achieve with this vehicle which will easily cost you more than the car is worth.