258CI 4.2L

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   Was wanting to know if anybody knows anything wrong with the 258CI 4.2L AMC engine what are there good an bad points?

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kalve Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/04/2012 Location: Charleston WV Status: Offline Points: 279	Post Options Post Reply Quote kalve Report Post Thanks(0) Quote Reply Topic: 258CI 4.2L Posted: Nov/06/2012 at 2:59pm
	Was wanting to know if anybody knows anything wrong with the 258CI 4.2L AMC engine what are there good an bad points?

AMC1320 Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Apprentice Joined: Oct/22/2012 Location: Manchester, TN Status: Offline Points: 152	Post Options Post Reply Quote AMC1320 Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 3:30pm
	One of the best, if not THE best straight six ever made, in my opinion Rob

danleym Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Oct/17/2009 Location: Colorado Spring Status: Offline Points: 850	Post Options Post Reply Quote danleym Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 4:06pm
	Cons: Not high revving, not a whole lot of horsepower. From the factory, at least. Both of those can definitely be helped with the right parts. Pros: Extremely reliable, all the torque you'll ever need, 40+ years of development and interchangeability plus a very active Jeep community means there is a good amount of aftermarket upgrade/replacement parts available- not as much as a Chevy 350, but there's not much you can't find with a little searching. Oh, almost forgot- straight sixes are cool.
	Hollis Danley 1980 Spirit, 258 2000 VW Jetta TDI 2002 Jeep Wrangler, 4.0 2015 Subaru XV Crosstrek

Pdok Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025	Post Options Post Reply Quote Pdok Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 4:25pm
	Absolutely solid motor. Weighs a freaking ton, however, dang near as much as my Buick 350, near as I can tell (probably not.) Not the easiest thing to get all the nuisance oil drips fixed on, basically expect a drip at every corner up front, and probably change that valve cover gasket every couple years. If it stops dripping, you're out of oil. Rear main seals have a way of dripping, if mine is any indication anyway. I've heard Jeepers say that too. Love the fact that the intake/exhaust are opposite the spark plugs, dist, fuel pump, etc. Super torque, easy to modify with the 4.0 head swap. Very easy to pull the head and work on the top end. Tons of common parts available across many years of production. Lots of inline 6's have great reps, though, to be honest. The big Chevy I6 I had in a 53 Hydrocrane chassis was bulletproof and all we ever did was add oil (lasted forever.) Ford has great I6's for the most part, too. Can't speak for the slant-6 Mopar crowd, but they love theirs. There's something about an old-school 6 that I really like, can't tell you exactly what it is. I never liked any of my V8s as much as my 4.2, though.
	76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.

kalve Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/04/2012 Location: Charleston WV Status: Offline Points: 279	Post Options Post Reply Quote kalve Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 6:42pm
	ok thank cause I am going to look at a 85 AMC Eagle wagon this weekend that has the 4.2 in it an the guy tell me it is all factory an has been sitting since 04 an not started or drove any. I am probably going to buy it but want all the info I can get on it before I go look at it.

Pdok Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025	Post Options Post Reply Quote Pdok Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 6:53pm
	I'd be way more worried about fuel going bad inside all the tank/filter/pump/carb and not so worried about the motor itself. You should consider an oil purge/change before cranking it up. You can buy some really cheap oil, and change the oil (not filter). Put in a pint of Berryman's B-12 then pull the distro and use an electric drill and one of those pump shaft turners for about 10-15 minutes to get the sludge moving. Change the oil again and just put some normal oil in with a new filter. Run the oil pump for another 5-10 minutes then. Might not be to everyone's tastes, but it seemed to help me get some of the smaller crud out of the passages with mine. I got my Gremlin from somebody who had it sitting in his garage for about 10 years. I pulled the valve cover and saw about 1/4 inch of dried sludge sitting in there. I went ahead and pulled the head and there was quite a bit of buildup. The head was awful, so I'd at least pull the valve cover and run the oil pump to see if you're getting lube at all the rockers. At the same time you can check the rocker bridges for wear and see if they need to be retorqued or if any one of them has been starved for oil. In my case, the back two had blockages that had kept oil from getting to the rockers and I could see it on the cam after I pulled the head (which I had to do anyway after I saw the sludge.) On the other hand, if you just put good gas in the system and carb, the sucker would probably fire up and run forever as is...ha! Maybe I'm too OCD. Your gas is certainly bad, and I would ABSOLUTELY NOT run the engine without purging the tank and whole system!! Been there, and it got expensive.
	76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.

kalve Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/04/2012 Location: Charleston WV Status: Offline Points: 279	Post Options Post Reply Quote kalve Report Post Thanks(0) Quote Reply Posted: Nov/06/2012 at 6:59pm
	yea I bought a 70 Cougar hardtop that had been sitting bout 4-5 years without being started an we took the fuel line loose from the carb an got most of the gas out of the tank an put fresh gas in the tank an poured some in the carb an let it run for a while an it was fine been there done that.

farna Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19676	Post Options Post Reply Quote farna Report Post Thanks(0) Quote Reply Posted: Nov/07/2012 at 8:26pm
	The only real bad thing about that particular year six is the plastic valve cover. They are notorious for leaking after a few years. There are replacement metal covers, you just need to get the right one for the year engine you have. It's darn near impossible to get an old plastic cover to seal! There are a good many pollution control hoses and such under the hood, but don't just yank it all off! With it all working the engine will run better than with it removed, though if some of it isn't working right it will run better with none of it on. So it can be fun figuring out what to do there! Most of the time it's just old vacuum hoses causing 90% of the issues. There could be other problems, but if it runs good you're way ahead of the game! If you do yank all the pollution control stuff off be prepared to locate an older non-pollution control distributor and carburetor. Not real hard to do either, but try running the pollution control parts without everything working and it just doesn't run well.
	Frank Swygert

kalve Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Nut Joined: Nov/04/2012 Location: Charleston WV Status: Offline Points: 279	Post Options Post Reply Quote kalve Report Post Thanks(0) Quote Reply Posted: Nov/07/2012 at 8:51pm
	I am planning to go look at the car sat. morning an take some gas an a battery an see if I can get it to turn over an hopefully start. By what the guy told me on the car its all stock nothing changed on it. It sounds like a good one if it is in as good of shape as he says an starts an stuff then sold. I know the valve covers an the carb is the problem with these cars so I am planning to swap the covers an I got a ford motorcraft 2 barrel carb I will put on the car to get it running better.

Pdok Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Apr/03/2011 Location: Alabama Status: Offline Points: 1025	Post Options Post Reply Quote Pdok Report Post Thanks(0) Quote Reply Posted: Nov/08/2012 at 6:42am
	If you swap carbs, there will be some important choices to make about what emissions connections to keep hooked up. The Motorcraft is a good choice overall. I'd keep EGR and whatever charcoal canister connections there are. Lots of the temp sensor connections could be disconnected, but like farna said, you can't really pull just some of it. At least without understanding what it all does. If the 1985 carb is hooked up to an ECM, then you've got that to deal with. The Nutter bypass is a pretty common option if that's what is on there (I am not sure of the year groups where it all started.) http://www.4x4wire.com/jeep/tech/electrical/jn-ignition99/ The smog distributors also had advance limiting that kept total advance way down. You can mod the one on the car with a little dremel skills. That's a Google project on the Jeep forums... Sounds like a pretty easy project if the thing runs when you get there...good luck.
	76 Grem X 258/904,4.0 head/MPFI, Comp X250H cam, Hughes springs, Clifford header, serpentine swap.