4.2 to 4.0 head swap

[mudoctor]

Newbie Here! Need some help on a head and carb conversion. My son and I have a 1987 yj wrangler, 4.2 258 block casting number EF3235444. Head casting number 8933002, it has 7/16 head bolts. I purchased a 2150 motorcraft carb to swap out the carter and ordered a set of Pacesetter headers to install with a new dual exhaust fot it. anyway the headers do not fit. Part number 70-1191. I think they actually fit a 4.0 in a cherokee or something. But with this I am now thinking of changing the Head so I can use the headers and gain the extra HP. Question, will a head casting 7120 from a 4.0 (or what year) fit with the water holes blocked off, second head bolt size? ( my OEM 4.2 has 7/16, will the head of a 4.0 be 7/16 or 1/2) third can I use my OEM intake with my 2150 motorcraft carb? fourth will the PN 70-1191 pacesetter headers fit it? Some direction on this would really help. This project has got both me and my son frustrated. Thank You Mudoctor

[bbarrett]

Newbie Here! Need some help on a head and carb conversion. My son and I have a 1987 yj wrangler, 4.2 258 block casting number EF3235444. Head casting number 8933002, it has 7/16 head bolts. I purchased a 2150 motorcraft carb to swap out the carter and ordered a set of Pacesetter headers to install with a new dual exhaust fot it. anyway the headers do not fit. Part number 70-1191. I think they actually fit a 4.0 in a cherokee or something. But with this I am now thinking of changing the Head so I can use the headers and gain the extra HP. Question, will a head casting 7120 from a 4.0 (or what year) fit with the water holes blocked off, second head bolt size? ( my OEM 4.2 has 7/16, will the head of a 4.0 be 7/16 or 1/2) third can I use my OEM intake with my 2150 motorcraft carb? fourth will the PN 70-1191 pacesetter headers fit it? Some direction on this would really help. This project has got both me and my son frustrated. Thank You Mudoctor

According to summit those headers fit from 87 to 93 Cherokee, That is actually the header i have on my jeep now, Which by the way is a 87 YJ. I did the head swap before i built my stroker motor and ran it that way for better than a year. Mine didn't have the 7/16 bolts, But as i work on small block Fords which have the 7/16 bolts i feel the same fix would work for a Jeep.
http://www.summitracing.com/parts/TFS-51400419-1/
I used a Weber for a carb so i cant say much about the Motorcraft, Other than they are good carbs, (again a Ford product) U will have to custom fit the header to the exhaust if yours was like mine, But this is just a simple hook up. I used the 0630 casting which by most accounts is the same head. I would be sure the temp sender hole at the back of the head on the drivers side is tapped , because this is the hole used in the original head, Unless u don't mind cutting and splicing the original wires. Some say the intake wont fit (4.2 intake) But mine did. I did have to remove the dial pin locator holes. I just cut the bottom out of the holes. I had to elongate the power steering bracket holes to match the intake being raised up. but again its no big thing.Don't forget to stop up the water holes in the head, unless you have a block that is not scalloped.(i have never saw a 4.2 that isn't, but i have heard they made one) I used Quick-steel and packaging peanuts to stop mine up and had no problems in the year i used it that way. As far as the power, U will notice a difference, Especially if the jeep wasn't running good before. Pinging went away on mine and it seemed to want to pull father in the rpm range. But If your Jeep is was in good tune you wont notice much of a power difference with the new head. Hope this helps

[mudoctor]

bbarrett, You mentioned that you stroked your engine? What did you do? I was reading that you can take a 4.0 and install a 4.2 crank, rods and pistons? will that work or what other options do I have.

[bbarrett]

bbarrett, You mentioned that you stroked your engine? What did you do? I was reading that you can take a 4.0 and install a 4.2 crank, rods and pistons? will that work or what other options do I have.

I did "stroke" my engine, I found a 1987 4.0 block from a Cherokee, used a 258 crank and 4.0 rods with a 060 bore. This gave me a 4.7 or 287 CI engine. Stroking a 4.0 can be done many ways. There is the "poor mans" way all the way up to over a 5.0 liter. It just all depends on the funds available.I like the long rod (4.0 rods) because the piston is custom made, therefore the skirt doesn't come out the bottom of the bore as much as with the 4.2 rods and stock pistons. You also get the advantage of a longer roded motor. But whichever way you go, Be sure of the machine work. I made a couple of mistakes that i would correct if i build another one.My advice to you is to search this site (it is the most complete site i have found for info on stroking the 4.0 engine) There is some things that is not mentioned here but 98% of the info is here. Read reread and read again before you buy the first part. And keep us informed of your progress.

[CAM80Z28]

YOU SHOULD TRY A EDLEBROCK 600 (1405) I JUST DID ONE FOR A GUY WORKS FANTASTIC EXLENT RESPONSE OUT OF THE BOX ( MR GASKET ADAPTER #1933 ) BOLTS STRATE ON

[supersport126]

Newbie Here! Need some help on a head and carb conversion. My son and I have a 1987 yj wrangler, 4.2 258 block casting number EF3235444. Head casting number 8933002, it has 7/16 head bolts. I purchased a 2150 motorcraft carb to swap out the carter and ordered a set of Pacesetter headers to install with a new dual exhaust fot it. anyway the headers do not fit. Part number 70-1191. I think they actually fit a 4.0 in a cherokee or something. But with this I am now thinking of changing the Head so I can use the headers and gain the extra HP. Question, will a head casting 7120 from a 4.0 (or what year) fit with the water holes blocked off, second head bolt size? ( my OEM 4.2 has 7/16, will the head of a 4.0 be 7/16 or 1/2) third can I use my OEM intake with my 2150 motorcraft carb? fourth will the PN 70-1191 pacesetter headers fit it? Some direction on this would really help. This project has got both me and my son frustrated. Thank You Mudoctor

Did you ever get this project running? I just finshed mine and have a couple question on valve train