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Discussion Starter · #1 ·
I just traded work for a 91 Explorer with either a cracked head or blown head gasket allowing water into the crankcase. I have tried to find a good site for info but came up with nothing. I would rebuild it but was told the older 4.0's were junk and I should go with the newer style. There is a new one on ebay for close to $2000. I figure if I rebuild the original I will probably be close to $2000 with machine work and parts especially if the heads need replaced. Now the question-are the old ones junk? How much trouble would it be to convert it to the OHC 4.0? How much trouble to put in a 5.0? It is for my daughter so more economy would be better than horsepower. Any advice would be appreciated. Thank you.
 

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i have a 93 and i dont think the engine is junk. did a rebuild on mine and i think it was worth it. here is a good site for the explorer you can not put a 5.0 in the early explorers with out replacing the computer wireing trans rearedn driveshaft. the 91-94 only had the 6 cylinder
 

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Well, the 5.0 ones only came with AWD (thats what Ive been told) so I dont know how the swap would be - in addition, the mileage was always much worse (but that may have been due to the AWD). I can say that most exporers are underpowered but I have had the older 4.0 and the SOHC version and the new SOHC is much nicer.....
 

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The heads are bad and prone to cracking,the blocks are a pretty hefty piece and go many miles with little bore wear.
Pull the heads and have them magnafluxed paying extra attention to the area from the valve cover mating surface to the spark plug holes
 

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94 mazda b4000 with 214000 miles still runs good
 

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67 coupe, 69 Sportsroof, 86 hatchback
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Before you get too far out there, you'll probably want to inspect what you have. The earlier 4.0's are not "junk" that I'm aware of. They are sensitive to overheating like almost all later model engines. You may be able to replace a head and put the engine back into to service. Only a teardown will tell. If the cylinders and bottom out seem to still be in good shape, it's likely worth the money to have the heads checked out. Just because an engine has run hot doesn't necessarily mean it needs a rebuild.
5.0's weren't put into Explorers until "generation II", or the 95 and newer body style. It may be possible to retrofit the complete drivetrain, but it would cost about as much as another good used Explorer.
The "early" 4.0 SOHC engines are the ones that have a rap for being lemons. Mostly from the timing chains stretching out and slapping. A problem Ford claims has been taken care of in the latest OHC versions, but it's still driving many 96-8 SOHC owners nuts. It's interesting that you and I can't replace these timing chains. It takes a Ford-trained tech about an hour to line the replacement chains and cam timing back up using Ford-specific service tools available ONLY from Ford. I watched a guy do this and was amazed that it actually was that complicated. It is truly ridiculously difficult. I have since fore-sworn anything to do with any SOHC 4.0 engine. Period.
SWMBO's plain old 4.0 in her 94 Explorer is still happily ticking over at 158K miles.
 

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I am having a tough time trying to decide which engine to put back in my 93 Ranger. I'm at 181k and using a quart of oil every 1k. If I keep my Ranger I will probably just put a new 4.0 back in it. But I do have dreams of a 5.0 or a SOHC 4.0 or dare I say an abnormally aspirated 4.0 :: Oh yeah the SWMBO would really go for that one. Yes dear the cost of my engine really does cost the price of a new used Ranger. :p fd
 

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Discussion Starter · #9 ·
Thanks to all of you! I have started pulling the top end and nobody would believe the condition of two spark plugs. One had NO electrode,center, or porcelan. The other one had to be firing to the plug base. When I pull the heads tomorrow hopefully the parts from the first plug didn't scratch the cylinder walls. Thanks again!
 
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