Originally Posted by Jeep_Fanatic
my 2.8L is crappy right now. 2 of the rings are going bad and the vacuum system is horrible. it still gets good highway power but gas is like 10mpg.
I was thinking of looking into ordering another 2.8L and beefing it up a bit for hp/torque, then swap it into the MJ in case I build it up.
i know I can bore and increase compression through a machine shop. but is there a kit available? like camshaft, valves, rockers, rings, etc etc. or superchargers/turbos?
Don't bother with another 2.8L. Most of them are FWD anyhow - and therefore have the starter motor on the wrong side for RWD/4WD mounting.
The V6-3.1L and V6-3.4L engines are WORLDS apart! (And, easier to find.) All three engines (in RWD/4WD trim) use the same mounting pattern for the transmission and chassis mount brackets, so they'll swap freely. You can either put the V8-2.8L 2V intake on the 3.1L/3.4L engine (with a slightly upsized carburettor,) or bring along the fuel injection setup with the new engine (which you should do anyhow.)
While you're looking for a donor engine, look for a 1988 or later S10 4WD to pull the powertrain out of (if you have the automatic, with the "Baby 904.") You can adapt the transmission mount x-member to mount up the THM700R4 - which is a better transmission (the earlier versions are barely fit for scrap metal,) stronger, better gear ratios, and has overdrive.
It is also usually paired with the NP231C transfer case, which uses a 1.25" wide Morse drive chain (instead of the 1.00" wide Morse in the NP231J.)
If you luck out and find a V6-3.1L/4L60/NP231C combo, grab it!
I'd also grab the output yoke for the rear driveshaft, you may need it to adapt your "Baby 904" driveshaft (I think they use the same series of U-joints, so that's less of a problem. 1310, I believe?)
Note that the much later version of the 4L60 is the 4L60E
, which is electronically-controlled. However, I don't recall if they're found behind the V6-60 - and the ones behind the V6-262 (4.3L) engine won't bolt up to the 60-degree V6, since the V6-262 uses the "GM V8" bellhousing pattern, not the "GM Metric" pattern used by the 60* (2.8L/3.1L/3.4L.) I do not believe that the THM700R4/4L60 has a removable bellhousing.
You can also net a similar advantage if you source the manual transmission behind the V6, if that's what you're replacing. I believe the T4/T5 used in the S10 was a bit tougher than that used in the Jeep, and the transfer cases are otherwise the same (NP231C vice NP231J, difference in drive chains.) However, I believe the GM and AMC T4/T5 transmissions use the same mount, it is the internals that differ. (Input splines should be 1.125"-10 in both cases, but I can't swear to the pilot diameter.)