4.0 Head compatibility question

Does anyone know if the head off of a 4.0 HO (91) will bolt on an 89 4.0 "low output" motor? Will the intake manifold off of the "low output" bolt to the HO head? How about adapting the "low output" throttle body to a 99 or newer intake? I'm thinking about building a stroker motor for an 89 XJ and I'm trying to make the motor breathe as well as I can. TIA for any advice/criticism.

MIke

All 4.0 heads will bolt on to any 4.0 block. The renix manifold needs to be modified to work with the HO head. The HO manifold flows better the 99+ being the best if you can get one. I just built a stroker for my 89 and I used an HO head, manifold, and TB. If you want the motor to breathe well, do not use the Renix tb it is too small. If you compare the two you will see the difference, the renix is 53mm and the HO is 61mm. Check out Dinos site for performance mods, he has a good porting write-up.

From what I under stand. The 4.0 heads will fit any L-6 AMC from mid 60's to now.

Pretty common - the 4.0 head is also often found grafted to the old 4.2L block!

The Renix manifolds will work with some modification, as the dowel pins are raised about 1/2" or so on the HO (I think.)

You might want to check the "strokers" egroup (groups.yahoo.com/groups/strokers) for more information on this - it's a common mod and has been hashed out pretty well there.

If you are going to do the swap and can get your grubbies on a 99-up intake, also not a bad idea.

CAVEAT - the HO manifolds do NOT have provision for the EGR setup. Depending on your local emissions regulations, you may have to modify the Renix manifold to mate to the HO head, and may be letting yourself in for more work than you are ready to take on. Consider yourself warned...

5-90

I wouldn't even bother swapping a HO head onto the non-HO block. Just port the non-HO head and you can achieve comparable airflow numbers to a ported HO head. You'll just need to do more work especially on the rooves of both the intake and exhaust ports. Go to the "ported head" page of my website for a few tips. Get a 3-angle valve grind done to improve airflow at low lifts.
You can also keep your non-HO intake manifold and just port match it to the newly ported head.
Finally, you can graft a HO TB onto your non-HO manifold by using Joe Attardo's adapter plate. There's a link to his article on the "intakes" page my website. Remove the taper below the throttle plate so that the whole bore is 60mm.
If you follow my suggestions, the only new part you'll need is a HO TB, and you can find a good used one from a junkyard cheaply. Make sure it's from a '91-'95 Jeep 4.0 (they're the same on the XJ, YJ, and ZJ). You'll save a bunch of cash by keeping your original head.