4.0 and 4.0 HO, whats the difference?

lussenden · #1 03-12-2006, 11:46 PM

im just curious as to know what are the differences of the HO 4.0 and the 1990 and below 4.0. i have a 1990 and its really hard to find aftermarket parts for it. everything is for 1991 and up, so what are the real differences?

lussenden · #2 03-13-2006, 01:35 AM

they sell parts like headers and valve covers and throttle bodies for the 1991 and up. but i didnt think the engines were that different. i can hardly find anything like that for the non HO version

fredjacksonsan · #3 03-13-2006, 02:48 PM

IIRC, the difference was about 15HP, and maybe the head was redesigned.

StvDiego · #4 03-23-2006, 02:26 AM

Try http://www.xj-armor.com/ for throttle bodies, spacers, intakes and various stuff for early XJ's (btw, I've heard some complaints about these folks but I have bought several times from them with no problems; headers, lift kits are fairly easy to find but quality ones aren't cheap (found mine on eBay). It's out there, just takes a bit more looking and is generally more expensive.

AlohaBra · #5 03-29-2006, 11:57 AM

The 4.0 engine was made into the HO version in 1991 with changes to the head, camshaft profile, and the block castings.
In 1996, the 4.0 L got lighter pistons, a new head with better exhaust flow, a new exhaust manifold and steel valve covers.
In 1997, the block was tweaked for new a oil filter mounting for production compatiblity for the Grand Cherkokee.
In 1999, other block changes were made to the block, camshaft, rockers and head.
In 2006, production for the 4.0 L will be stopped with the 06 Wrangler.

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