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View Full Version : 4L Ho head onto a 4.2 block??


Jeep eh
05-30-2006, 02:13 PM
Anyone ever done it before?? if so was it worth it any better gas milage or HP increase??

Jeepnut
05-30-2006, 02:18 PM
Yup its been done before. Its called a stroker motor....you can contact Matt at Jeep Thrills he has done a bunch off them or Mikey [nutbar] on this board[cheers]

Nutbar
05-30-2006, 02:26 PM
Sorry Johnny but that is not the "Stroker" mtr

But yes it has been done, I have done it myself, yes you will get lots of advantages by doing it . . . more efficient fuel management system so therefore increased fuel mileage and power, the head flows better so you get a real increase in top end power and retain the torque of the long stroke 4.2.

If you do decide to do the swap make sure you use the parts from the 91 and up 4.0 and for the computer and harness use the 91 to 95 yj to make it simple for the install, DO NOT use the stuff from the 87 to 90 Cherokee ( XJ ) 4.0 the Renix system was very problematic and complicated for swapping.

Jeepnut
05-30-2006, 02:30 PM
wrong again....insert big sigh here[16]

epic3
05-30-2006, 08:20 PM
whats new
just part of aging
Just do it gracefully and less people will take notice

Matt
06-01-2006, 07:20 AM
wrong again....insert big sigh here[16]



getting used to it yet[f]

Jeep eh
06-04-2006, 06:40 PM
well a found one at pick and pull its a 90 xj but im sticking with my old intake manifold but using the exhuast manifold from the xj i dont feel like changing the wiring harness over i just want my jeep back on the road

Kel_CJ8
06-04-2006, 08:24 PM
I have got a running 4.2L complete if your interested?

Nutbar
06-04-2006, 08:37 PM
well a found one at pick and pull its a 90 xj but im sticking with my old intake manifold but using the exhuast manifold from the xj i dont feel like changing the wiring harness over i just want my jeep back on the road

DO NOT use the parts from the 90 XJ you will not be happy with it makes for a complicated install. Use parts from the 91 and newer then alot of parts can be scavenged from YJs to make the swap easier.

Jeep eh
06-04-2006, 09:05 PM
DO NOT use the parts from the 90 XJ you will not be happy with it makes for a complicated install. Use parts from the 91 and newer then alot of parts can be scavenged from YJs to make the swap easier.


im not using the intake manifold from it tho im puting my carb back on so is there so i didnt think there was any difference between the achual head from a 1990 compared to a 91? am i wrong??

Jeep eh
06-04-2006, 09:07 PM
I have got a running 4.2L complete if your interested?
thanks for the offer but ive already sent my block to the machine shop to get bored and im caming it and putting the 4L head on it

dawb
06-04-2006, 10:11 PM
http://monsterslayer.com/jeep/40Head/40Head.htm
the water jackets need to be welded up and head resurfaced

And the stroker is when you take the crank and pistons from a 4.2 and use the 4. block and head right? (basically)

Nutbar
06-04-2006, 10:19 PM
im not using the intake manifold from it tho im puting my carb back on so is there so i didnt think there was any difference between the achual head from a 1990 compared to a 91? am i wrong??

Yes there is a huge difference between the 87 to 90 4.0 and the 91 and up 4.0 heads the port shape and placement is way different between the two. 91 and up have improved flow characteristics and better combustion chamber design.

Also you better check that the ports and gasket on the 4.2 intake will seal on either head I think with the size of the ports on the 87 to 90 4.0 you might have intake vacum leak issues

Nutbar
06-04-2006, 10:31 PM
http://monsterslayer.com/jeep/40Head/40Head.htm
the water jackets need to be welded up and head resurfaced

And the stroker is when you take the crank and pistons from a 4.2 and use the 4. block and head right? (basically)

If you read the article a little closer you will see that not all of the heads need to be filled it says that it can be an issue for leaking but not always.

I have done the 4.0 head and inj on the 4.2 and have not had to modify the water passages on the 4.0 head.

dawb
06-05-2006, 09:21 PM
me and reading dont go to well together :D

Matt
06-07-2006, 07:19 AM
why go to all the work of changing to a 4.0 head and still use a pos carb!
what advantage do you think you will get?

Jeep eh
06-07-2006, 10:47 PM
better designed intake and exhaust ports u can c a huge difference by just comparing the two one of the biggest aspects why the 4.2 is so bad on gas is that is doesnt breath enough the air coming in has to make almost a 90 degree turn and im not saying i wont change it to fuel injection in the future i just am out of money and my jeep has been off the road for two months now and i want it back

jeeper
06-07-2006, 10:55 PM
Hey jeepeh


MAtt and nutbar are givin years of experiance of info hear -appreciate it !

Jeep eh
06-07-2006, 11:25 PM
o i apreciate it theyve given me a lot of useful advice but i have been told by an engine machinist that has spend 30 years increasing the horse power in engines and building 1900hp race engines that i will c a difference becuase it is a better designed head but i know i would c alot more if i fuel inject it but i am only 17 years old and i have already spent 2grand on a new frame and tub and carb(before i decided to do the head swap) and engine bore so im out of money for the time being

jeeper
06-07-2006, 11:29 PM
Those two know JEEPS better then anyone in the lower mainland ----Listen to them before someone that does every kinda motor !

Jeep eh
06-07-2006, 11:41 PM
ok well my engine is already apart and i already have a 4L head and exhuast manifold so i think its still worth it to put it on because i can always fuel inject it later when i have money and if my old intake manifold doesnt fit i will go back to pick ur part get the fuel injection and change take my wiring harness back off and change it but i really just want to get my jeep back in the bush