Thanks..That was a lot to type....(glad I didnt have to)
Im looking to increase low end torque for off roading. I noticed a lot of the power kicks in around 3k rpm. I got a tight budget right now (no job) (school). I have a 2000 XJ with a 3 inch lift and 31 inch tires bone stock engine
OBD-II will make your job a bit more difficult (if you change something too much, it will throw codes at you...) and I don't know what the smog regs are like in NYS. Can't be as bad as here in CA, tho.
The good news is that more "bolt-on" parts are going to be available for you than for me (I have RENIX, which is pre-OBD and there aren't an awful lot of "California-approved" parts available...) but the gains from them are going to be minimal. However, they should complement a cam swap easily - and I've used Crane, Comp, or Isky cams on various engines with good results. I'm sure Crane and Comp make cams for the AMC six, and there's an outfit called Lazer (found them when I was researching the
Power Manual) thta have promising numbers.
Recall that an engine is little more than a large air pump that generates power, and it needs less power to run than it generates. What's left gets split three ways (cooling system, exhaust, motive power) and all you're trying to do is make more power. It's still going to get split - but you're going to move up.
How do you make more power? You need to burn more fuel. In order to burn more fuel, you'll need more air - which means that most engine power adders are going to be concerned with helping the engine move more air through itself - by opening up the exhaust, opening up the intake, and then altering camshaft timing.
What I'd do? Find a #0630 (1996-1998/1999) or a #7120 (1991-1995) cylinder head, and get ready to bolt that on. Both heads will have more exhaust flow than your #0331 head, and the #7120 also shows a marked increase in intake flow (since your intake manifold and throttle body will support the flow, the cylinder head port is the next restriction that needs to be eased.) You'll need an adapter for the exhaust manifold - but there's a thread around here somewhere for someone who has designed a plate and is selling them - for #0331 to #0630 conversions, but it should be able to be made to work with the #7120 head as well. Keep your later intake manifold - it flows better. You'll also need to fabricate bracketry for the coil rail pack you have - the #0630 and #7120 heads don't have the mounting bosses for it - but that shouldn't be too much work.
If you've lifted, get a new downpipe made. If you haven't, you may not need it unless you're building a stroker anyhow. Either way, get a more free-flowing muffler (you don't need a glasspack, but I've heard good about the Flowmasters and the like. I've actually been using Walker Turbo II mufflers - about twenty bucks at the local - and I've been happy with them. BD - Butt Dyno - does show a slight increase in power, they sound nice, and they're cheap.) Next thing to tackle in the exhaust is the catalytic converter - I've had good luck using BBChevvy "universal" converters on my RENIX rigs, but I'm not sure how well it will work with OBD-II - it should tho - since I've not failed a California emissions check using them. Your 2000 likely has "pre-cats" and main cats - see what you can do there (I haven't done much research.) Make sure you can replace the HEGO sensors in the manifolds; the bung is a standard size, and if the part you're using doesn't have them, any competent exhaust shop should have a boxful and can drill and weld them wherever you need them.
As I said earlier, you don't really
need the bored throttle body - the main thing you're going to notice there is part-throttle response, rather than an increase in torque output. So, save that for later (and note that you can usually get away with using later Ford small block throttle bodies, making them easier to find.) Essentially, if you "blip" the throttle with a bored throttle body, you're going to see the effective opening open up faster - which is what makes for faster response. It's a simple swap - you don't need to do it, but if you want quicker response, it's an idea.
Once you've sourced your replacement cylinder head, have the ports cleaned up and polished (it's a "dry intake" setup, so you don't have to worry about fuel puddling. You don't want a mirror finish, but you don't really want the "sand-cast" finish either.) to improve airflow.
Do not change the profile of the port - just clean up the surface. Don't do anything to change the profile of the port unless you have a flowbench - it's painfully easy to screw this job up! Standard Abrasives has an excellent writeup on their site to do this very job, and they're also a good supplier of abrasives for the job (you'll find an air-powered die grinder to be best for the job, believe me.) Smooth out the cast surface of the combustion chambers as well, and be sure to "break" (gently!) the sharp edges where the machined surface meets the cast bowl - this point is a heat riser, and breaking this will help to keep detonation down. Don't remove a lot of material - feel it before you start, gently hit it with the abrasive, and feel it afterwards. All you really want to do is round it off slightly -
that's it!
Once you've done with the airflow bits, go over the head and make sure you don't have any flash from mould parting lines anywhere - heat risers, again. Cleaning casting flash up will help to improve heat rejection.
All parts should have casting flash cleaned off of them.
If you take the head in for work, specify a "three-angle" valve job (which you should get anyhow) - a "five-angle" is more work than you need, and more money than you want to pay. Don't bother changing the size of the valves - it's also more work than you need to have done.
That should be enough to keep you busy for a little while. Let me know if you need more...