Add another 40 hp to your 4.2 6 Banger!

SupaJosh · 12-27-2006, 09:22 PM

I found this awesome write up on how to put more horse power maybe 40, he says, in my 4.2 by putting a 4.0 head on it and you don't have to rip the whole motor out either! Relatively simple I think...since I just rebuilt a dakota v-6.
http://www.geocities.com/035jeep/40L.html

The good thing is its fairly cheap mod compared to the hp out of it!
Good luck I will try it in about a month! I just got my 84 Cj7 back on the road!

**jeepskate** · 12-27-2006, 11:23 PM

People have been doing this for several years now. Probably the best site for info is the 4.0 swap forum (covers the head as well as the whole engine) over at www.cjoffroad.com

AMC Power · 12-28-2006, 11:13 AM

I am currently rebuilding a 4.2 and I did not go with the 4.0 head because I wanted to put a 4-barrel intake on it as well as a dual outlet header. I don't think you can do that with the 4.0 head.

gosupes · 12-28-2006, 11:23 AM

Quote:

Originally Posted by AMC Power

I am currently rebuilding a 4.2 and I did not go with the 4.0 head because I wanted to put a 4-barrel intake on it as well as a dual outlet header. I don't think you can do that with the 4.0 head.

Bet me.

Although the headers would have to be custom as no one makes duals for the 4.0 head. I wouldn't do the dual header because the 258 likes a little more backpressure for the low end grunt.

jadams68 · 12-28-2006, 12:21 PM

I did this mod a year ago.

http://www.bustedjeep.com/projects/rebuild.asp

SupaJosh · 12-28-2006, 12:52 PM

Quote:

Originally Posted by jadams68

I did this mod a year ago.

http://www.bustedjeep.com/projects/rebuild.asp

Nice and what were the results? More horse power? Run better? Better gas mileage? and what was it? Did you do the fuel injection?

jadams68 · 12-28-2006, 12:56 PM

- More power yes... I never put it on a dyno to get an exact measurement in horsepower tho.

- Fuel economy...not really because I have 35" tires with 4.56 gears and any fuel economy gained would be negligable.

- The head won't make it run better, just gives you power. To really make significant gains with a 4.0L swap, you need to put a fuel injection kit on it. I did a TBI Howell FI kit, however the real performance gains are made by a multi-port fuel injection system.

I love the results. It's as reliable as any modern vehicle. I never stall and it starts right up no matter how cold it is.

BIGM · 12-28-2006, 07:57 PM

For anyone who has done the 4.0 head conversion, what did the head and parts cost you?

GPER · 12-28-2006, 08:10 PM

I bought my 4.0 head for 125 bucks then about 350 to redo the head, drill, tap and plug the water jackets. Then Mopar rapes you for the valve springs to go with a torquer cam. They were 300 bucks with a Jeep Tech's discount. Crane springs were like 80 bocks but they didn't have the retainers and locks to fit.

gosupes · 12-29-2006, 08:39 AM

For me, it cost $250 for a rebuilt head and my 258 head for a core. I milled the jackets at work, it took about 45 minutes for setup and 20 minutes to mill the jackets for freeze plugs.

Fatman · 12-29-2006, 08:53 AM

Anyone use these guys for their heads?

http://www.cylinder-heads.com/

the 4.0 head water jackets are sealed new valves, seats, 3 angle job

http://www.cylinder-heads.com/store_items_view.asp?itemid=16135

"Chrysler Conversion 6 cylinder. Fits years 98-99, 4.0 ltr. Casting number 7120"

BIGM · 12-29-2006, 12:26 PM

Some of the links that give info on the conversion are dead. I have done some googling but nothing more informative. Anyone have any other good links? I was also wondering about http://www.cylinder-heads.com/ Looks like a good deal with the water jackets done.

badge1236 · 12-29-2006, 01:45 PM

Does this do anything to the realibility of the engine? How long will it last? Also, what year heads would fit on a '78 block?

jadams68 · 12-29-2006, 02:35 PM

I bought mine from Hesco which is probably the most expensive route, but I wanted it done right.

The link above to Clearwater cylinder head is a buyer beware. I first went with them and the head that was sent was defective. They gave me my money back, but I don't recommend them.

A 1978 block has the 1/2" head bolts which is great. Any 4.0L head with casting 7120 or 0630 will work. Mine is from a 1996 Cherokee.

gosupes · 12-29-2006, 03:24 PM

Quote:

Originally Posted by jadams68

I bought mine from Hesco which is probably the most expensive route, but I wanted it done right.

Hesco does have that aluminum head for just over $1800 for those with deep pockets.

12-28-2006, 07:57 PM	#8
BIGM Registered User Join Date: Mar 2005 Posts: 173 Profile Gallery Classifieds My Jeeps	For anyone who has done the 4.0 head conversion, what did the head and parts cost you?

12-29-2006, 12:26 PM	#12
BIGM Registered User Join Date: Mar 2005 Posts: 173 Profile Gallery Classifieds My Jeeps	Some of the links that give info on the conversion are dead. I have done some googling but nothing more informative. Anyone have any other good links? I was also wondering about http://www.cylinder-heads.com/ Looks like a good deal with the water jackets done.