jhc7399

Looking to have a friend help me with a rebuild on a 96 4.0 to put in my 99. Just curious what mods and what all parts you would replace on the rebuilt engine as new.

I plan on getting a 62mm TB, Injector upgrade, of course all usual tune up parts. Sending the block out and getting it back as a small block. The engine I am buying, seller says it had a 3 angle vavle job 3 months before he pulled it out so I will send that to a shop to have it looked at to make sure everything is good with that.

Any other ideas? This will be my daily driver hopefully for many years so fuel economy is a big deal.

Thanks

JeepCoMJ

Late 99 and up intake, apn header, 4.2 crank and rods, autolite plugs ("performance" plugs have negative effects on 4.0), hi flow tstat housing, and a good quality tstat.

BigBadBob

When I spun a bearing in my 96 XJ I decided to make it a 4.6 stroker. Forged pistons and crank, upgraded injectors, new water pump, valve job, and larger throttle body. I haven't noticed any reduction in city gas mileage and highway mileage has actually increased to about 15mpg. it's not a daily driver and I've only put about 3,500 miles on the rebuild (2 yrs ago) so I feel it's still breaking in. I have much more torque and a lot quicker off the line than the stock 4.0. Works for me. Good luck, Murf

JeepCoMJ

If you are only getting 15mpg out of any 4.0, you need to drive nicer, or regear to match your tire size.

24mpg out of my stroker...4.10 and 33x10.50 tires with auto trans.

Fred/N0AZZ

24mpg that would be the only XJ I have ever heard of that came even close to that. In fact 14mpg would be more realistic, my Lincoln Town Car only gets 24mpg on the hiway.

On the engine swap you will need to do something about the ECU switching to an engine of that year. You said your taking your engine to the shop (the 99 ?) and getting a small block back, do you mean a short block? If that's true just find an early 99 head not the one you have they switched mid year and have it rebuilt complete long block.

JeepCoMJ

Twice in that post you are wrong.

1.). XJ's are rated 18-19 stock. Stroker equals more power and torque. Power increased over weight maintained equals decreased fuel consumption as the engine doesn't have to work...so long as all other components (tires, gears) mathematically equate to stock ratio.

2.). You can run any 4.0 high output off of any year high output PCM, so long as all sensors and drives (distributor, flexplate) are used for the appropriate year connectors and torque converter bolt pattern (there were 3 different TC bolt patterns).

The 96 head is an improvement over the 99 head as the exhaust ports are economically sized.

zeecherokeeman

99 and up intake you lose horsepower

jhc7399

So I need to use all of the 99's electronics on the 96 engine and keep the 96 head. Which intake, I have heard the 99 and up is the better design? And use the 99 tk and flex plate?

JeepCoMJ

Incorrect. Late 99 & up increases intake volume x2, thus improving airflow and performance.

JeepCoMJ

Yes to all