86customanche Posted January 21, 2010 Share Posted January 21, 2010 I have a 86 MJ with a 2.5L that is running very rough. :headpop: I took it to the shop and they said that there are multiple problems with it and that I'm best off finding a 4.0 straight 6 out of an older model XJ. I was wondering what you guys think are my choices for either fixing my small, underpowered motor or finding and replacing it with a more powerful one. :help: Link to comment Share on other sites More sharing options...
DJM/78 Posted January 21, 2010 Share Posted January 21, 2010 Really , its personal preference . My opinion , find a 91"-95" 4.0 HO . If your going to do it , do it all ! There is an active thread on a 2.5 - 4.0 HO conversion , might help you out . :thumbsup: Link to comment Share on other sites More sharing options...
jimoshel Posted January 21, 2010 Share Posted January 21, 2010 Am I the only odd ball in this crowd or what? I feel the 2.5 is very adequate for a daily driver. No, I wouldn't want to pull a horse trailer or a load of hay over Wolf Creek Pass with one but I feel it's more than adequate for a DD. And despite my advanced years I still put my foot in it so don't accuse me of being a 40MPH old fart going down the inside lane with my blinkers on. I sill run a '65 GTO on the strip and I have a timing slip on my '68 Caddy at 112MPH. Unfortunately it's from The Colorado Highway Patrol and not a race track. So the point I'm trying to make is Them 2.5 engines are OK. However if you have the need for more power the question is how deep are your pockets? What can you do your self or what will need to be farmed out? IMHO the cheapest and probably best would be to swap for a 4.0. If that's not good enough for ya, go with a 455 Buick.Turbo charged of course. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 21, 2010 Share Posted January 21, 2010 If you don't have the time or money for a 4.0 swap, which would mean engine, tranny, harness, driveshafts, radiator, core support.... lot of work. I know of at leat 1 0r 2 used 2.5 engines in the classifieds section for sale, just drop a used engine in and hit the road, you can slowly rebuild your old one in the meantime if thats what you want and have it ready in case the used one goes. I am in the process of doing exactly that myself, bought a used running 2.5 on here for $100 with injector and all accesories, it will get rebuilt with a few performance upgrades, and in case anything happens to my current 2.5, which I have no reason to beleive anything will, Ill be ready. Its a really good engine if you don't mind that type of thing. You know what you say to guys that have really big engined cars, or super fast expensive sports cars??? " Sorry about your p3n1s! " Link to comment Share on other sites More sharing options...
Geonovast Posted January 21, 2010 Share Posted January 21, 2010 Really , its personal preference . My opinion , find a 91"-95" 4.0 HO . 90 was Renix, and 96 was was weird screwed up year for electronics. jimoshel- I've noticed that even with all your 2.5s, none of them had an AX-4. 2.5/AX-4 combo received 3.55 gearing and was somewhat a dog on it. Granted, I think my 2.5 is on its way out... but I'm thinking of going 3.73 axle gearing and rebuilding the motor with a generous bore, and a cam if I can find one. Link to comment Share on other sites More sharing options...
Pete M Posted January 21, 2010 Share Posted January 21, 2010 running rough could simply be an dirty fuel injector or bad sensor. I get the impression that your mechanic is trying to scam you into a LOT of unnecessary labor with a complete drivetrain swap. I don't trust anyone to touch my trucks anymore. Link to comment Share on other sites More sharing options...
LEAD_NOT_FOLLOW Posted January 21, 2010 Share Posted January 21, 2010 Being that you have an '86 fitting a 4.0L is not going to be "bolt-in". There are issues with firewall clearance... Link to comment Share on other sites More sharing options...
Geonovast Posted January 21, 2010 Share Posted January 21, 2010 I think the rad support differences would be more of a mentionable concern than the 5 minutes spent pounding on a firewall. Link to comment Share on other sites More sharing options...
jimoshel Posted January 21, 2010 Share Posted January 21, 2010 Really , its personal preference . My opinion , find a 91"-95" 4.0 HO . 90 was Renix, and 96 was was weird screwed up year for electronics. jimoshel- I've noticed that even with all your 2.5s, none of them had an AX-4. 2.5/AX-4 combo received 3.55 gearing and was somewhat a dog on it. Granted, I think my 2.5 is on its way out... but I'm thinking of going 3.73 axle gearing and rebuilding the motor with a generous bore, and a cam if I can find one. That's true. They all have the 4:11. Just proves the ole adage, Proper GEARING gets the job done. :cheers: Link to comment Share on other sites More sharing options...
jimoshel Posted January 22, 2010 Share Posted January 22, 2010 Really , its personal preference . My opinion , find a 91"-95" 4.0 HO . 90 was Renix, and 96 was was weird screwed up year for electronics. jimoshel- I've noticed that even with all your 2.5s, none of them had an AX-4. 2.5/AX-4 combo received 3.55 gearing and was somewhat a dog on it. Granted, I think my 2.5 is on its way out... but I'm thinking of going 3.73 axle gearing and rebuilding the motor with a generous bore, and a cam if I can find one. That's true. They all have the 4:11. Just proves the ole adage, Proper GEARING gets the job done. :cheers: Used to before every corner had a speed shop, you could send a cam shaft to any good machine shop and get any profile you wanted on it. Does anybody still do that? Supporter of the underdog and staunch believer in 2.5 equality Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 22, 2010 Share Posted January 22, 2010 There a company near Vancouver BC called Accelerated Motion that has a selection of cams for the 2.5, website is amotion.com. It says they are temporarily closed but the catalog will be updated in March and company back open in April. Theres a lot of good info there too on cam selections. When their catalog was up they had a selection of cams for the 2.5 from stock to wild. So far they are the only place Ive found that still lists cams for the 2.5, but if anyone else knows someone else who still does Id be very interested to know. Link to comment Share on other sites More sharing options...
DJM/78 Posted January 22, 2010 Share Posted January 22, 2010 Used to before every corner had a speed shop, you could send a cam shaft to any good machine shop and get any profile you wanted on it. Does anybody still do that? Supporter of the underdog and staunch believer in 2.5 equality There is a shop up here in the springs called Castrol GTX performance and machine . They will do anything you want . I had a couple of things done there . Hot tanking , true decking , porting and polishing , valve angles and blue printing . Over sized cams , polished cam lobes , titanium valves . Mostly on old Pontiac big block motors and a couple of chevy small blocks . They will build you anything . However , by the time you do all that , you can find a used corvette LT1 motor w/ram jet intake , slap that baby in there . With low gearing , it will be hard keeping the tires on the ground ! Or slap your Buick HO in there . Shut up and hold on !!!!!! :drool: Link to comment Share on other sites More sharing options...
jimoshel Posted January 22, 2010 Share Posted January 22, 2010 I got tired of being second at the stop light drags so I swapped a WW2 F51 Mustang 1600HP engine into my 87 MJ. Now if I could just figure out why my BA10 and D35 keep taking turns crapping out on me? Link to comment Share on other sites More sharing options...
dasbulliwagen Posted January 23, 2010 Share Posted January 23, 2010 running rough could simply be an dirty fuel injector or bad sensor. I get the impression that your mechanic is trying to scam you into a LOT of unnecessary labor with a complete drivetrain swap. I don't trust anyone to touch my trucks anymore. I agree. You need a second opinion on this. The 2.5 is a tough engine, and if you arent hearing any knocking noises from the lower end, it can probably be fixed with the electronics like the injector, o2 sensor, coolant sensor..... etc. Call around to a bunch of independant shops and ask if theres anyone there that has good experience with Jeeps of this vintage. Most of the independants have old timers that have seen it all. Good luck and let us know what you figure out. Link to comment Share on other sites More sharing options...
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