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4.0 or 4.2???

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jeep yj
4K views 57 replies 14 participants last post by  YJ4LIFE 
#1 ·
Ok I just recently purchased a 1987 YJ Wrangler Sport, i bought it for 2400$ which to me wasnt that bad and i am going to be using it as my daily. The issue im having is that all the emission controls have been striped of the motor, it dont bother me really but since i can look and clearly see that the motor has had someone in it....idk for sure if its the 4.2 that came with the jeep or the 4.0

Im new to the Jeeps..Sorta, my dad had a couple Willis Jeeps a 12v and a 24v mil specs and ive done Mud Pit Jeep ( in Ms and La )....

also ontop of just getting into this stuff, i just moved last week to MD and have no idea were good places are to get work done here since all my tools and welding machines are back in Mississippi lol
 

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#2 ·
like previous stated, the motor has been striped down to the Bare necessities lol which is fine with me cuz i dont plane on doing rock crawling with the truck so i wont be getting into extreme situation to need a FIJ motor, but the tuning is off badly on the carb, it runs fine down the road, im use to old school trucks since i perfer these old type of motor over the new computer BS. but im mostly use to stuff like race motors for mud drags, NEW motors really lol. but this one lags to start with heavy feathering of gas pedal then sometimes goin down the rd u have to continue to feather the gas when slowing down or stoping or slowing down to turn or it dies altogether....but when its running it runs great....
 
#4 ·
also as you can tell, the original air filter cover has been removed and the small "hot rod" style put on, which means the PCV has been removed and that stupid air filter placed in the valve cover....again to me with race cars this would be fine...but it seems like trash from 4x4 use would get in....plus as you can see it allows oil to get out...so is there a way to stop the oil from leaking out from there....i rather keep all the Emission BS off the jeep
 
#7 ·
Just looking at the photo, it looks like the carb may have been replaced with a weber or MC2100. This would be why most of the emission and and stock air filter have been removed. I would figure out exactly what you have and try setting the timing and adjusting the carb.
 
#8 ·
yes the carb was replaced, when i bought the jeep i got alot of the original stuff back...carb, air filter houseing and everything that was removed really plus the soft top and extras for it...im in Cockeysville, and i rather put it a shop in get the carb tuned up, does anyone know of a place for this near me?
 
#9 ·
PCV is connected to the carb, the filter is for fresh air into the motor. have run mine for years like that, no problems. its a 4.2, the 4.0 didn't have a mechanical fuel pump.
the carb doesn't look like the original carter BBD, take a pic with the air cleaner off.
 
#11 ·
PCV is connected to the carb, the filter is for fresh air into the motor. have run mine for years like that, no problems.
ive run them on new project trucks n cars before also....but never on any of my Mudtrucks...but my biggest concern is the oil that is being lost threw this, u can see it comes out the filter and runs down the back of the Valve Cover
 
#10 ·
your valve cover is an 8 bolt not a 15 bolt like on the newer 4.2's. have heard that some 87's came that way, first time I've actually seen one.
 
#12 ·
be sure your PCV is working correctly and the hose isn't plugged. I'm not sure about how its hooked to the carb, be sure theres vacuum there. your valve cover is an aftermarket made by omix ada (I mistakenly bought one for my jeep) there should be a baffle under both inlets to help keep the oil out.
 
#13 ·
i do have one line pluged idk what it goes to... like i said the previous owner to all the emissions controls off, and installed a new Carb. I have only 1 pic of the motor at this time since the jeep is at my GF's parents ( apart complex tows non tag vehicles)

the hose circled in red is the pluged line. and also i thought the PCV valve pluged into the Valve Cover and a line connected it to a vent in the Air Intake Cover.....i remember on a older chevy having to replace this since the ball was stuck in the valve....but like i said im new to jeeps. THANK Yall for all this help
 
#15 ·
its hard to tell in your pic but it looks like the PCV line is hooked to the top of the carb, it should be hooked to vacuum. on my old weber and the holley I run now the PVC hooks to a nipple in the adapter under the carb.
 
#16 ·
There are no good shops in Cockysville. I used to live there. Grew up not far from there actually and can still be found there a few times a month. Your best bet is to do it yourself. Any shop that does know what they are doing will charge an arm and a leg. And possibly your first born.
 
#17 ·
it actually interesting because in 87 and 88 the 4.2 had a plactic valve cover and yours has the aluminum it wasnt until 89 and 90 where jeep converted it to the aluminum because the plastic would warp under heat and cause the thing to leak oil but i would check to see if thats the original motor but with the things done to it i would say it is possible that the PO did an aluminum valve cover swap on the original engine
 
#18 ·
my 87 has a factory aluminum valve cover, some have it some don't.
but the OP does have an aftermarket valve cover, the insignia on it is omix ada
 
#19 ·
As you've already learned, you have a 4.2, not the 4.0. Also, as you've found out, that is an aftermarket valve cover. As for the carb, the connections don't match the Motorcraft 2150 I have in my '87, so I'm going to guess you have the Weber 36/38.

Tuning the carb is not that tough of a job. Do some Youtube searching and you'll find some great videos on how to make the adjustments.
 
#22 ·
thanx for yalls input, currently im at a stalemate, the jeep is at my GF's parents since my complex would tow it without a Tag....and i just moved here the 28 of last month and in the process of changeing my DL and insurance over to it....which is funny....my insurance had me pull out a 55k policy out on this jeep lol....evil thought lol........anyways i wanna get to work on this jeep but weather here sucks and i dont have a shop nor the tools to work on it....so MOST will have to be hired out...imma find a sears and save up for the mechanics tool set to get a complete full set of tools i need to get started again here.

to agree with previous statements about the motor, its a aftermarket Valve cover yes...and the Carb is aftermarket...idk what yet not till i go take a look when we visit her parents again.
also, im sure yall already know but im wanting to put offroad lights and some better drive lights on here...maybe some KC daylighters ( flood ) for driver lights and KC daylighters ( long ) for offroad use. Now the big question is...do they make a GOOD AFFORDABLE Alternator for this? since ill have lights and a Sound System in the jeep, or maybe another vehicles alternator will drop in? I use to own a CB Store so ive gone as far as dropping 4 18 wheeler ALTs in a custom belt n pulley system in a Suburban before but idk wanna do that with this jeep lol i wanna use the KISS method on all that i do here
 
#24 ·
Check your compression. I just yanked out a 4.2 for excessive blow-by. Worn rings let exhaust gasses past, which pushes oil up and out the valve cover aka that back "filter" (mine happened to be placed in the front hole, but same thing). I know, my PO had done a similar thing to my jeep. Lost a quart of oil each ride between burning some and losing the rest.
 
#25 ·
ok so i went and took some pictures of the carb, a couple things that the guy pointed out to me that the PO had done when we removed all the emissions stuff, can someone tell me WTF is the yellow Arrow pointing to and if the Bolt used as a Plug is ok ( red )
 

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#26 ·
found the name but nothing else that i can see has any markings of what size, also if i remember correctly in picture 2.....i do believe the choke is stuck open.... im use to deallin with 4 barrel edelbrocks in holleys lol
 

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#28 ·
ok so heres were stuff gets retarded....im not above Jerry rigging, but only for a Temp thing lol ok so i got this line shown in the Pix that has a stick used a plug lol and in Side 2 is were it leads to the carb...can i just take the hose off n plug it at the carb or atleast shorten the line and plug it correctly? also out the front the carb theres a split of 3....one is not pluged as well...does it need it?
 

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