New Engine? What to get?

hillie4life · 02-04-2009, 04:10 PM

So I dropped my smoke billowing 89 4.2 YJ off at the mechanics yesterday (i know i know, mechanics bad, do-it-yourselfers good...) but right now I just don’t have the time do deal with it and it is my daily driver so i cant afford to tinker for weeks.

Before this week I hadn't really thought of doing much with the engine but since I got word back this morning that my engine is definitely shot I was hoping you call could help me come to a decision. of

The easy, least expensive route would probably be to find another 4.2 and just throw her in there... but I've been beginning to have dreams of grander.

I've done a little surfing on the subject and the common upgrade seems to be a 4.0 conversion, but that usually is when the 4.2 is fine and people are just doing an upgrade... my 4.2 is dead.

So I figure, he's taking the engine out... I can put whatever I want back in, but the abundance of knowledge on the web has left me undecided, so I hoping you all could give me some input.

Now I dont have all the money in the world but I figured that while the thing is in the shop this might be a good excuse to big. Granted I still need to be somewhat realistic to keep that in mind... It is my daily driver but I only have a 15 minute commute and I've been only getting 10 to the mile for a while....So what do you think?

Stick with the 4.2? go 4.0? I've seen a v6 swap? go v8? which one? GM? AMC? CHEVY? 350? 360?.... etc etc... I'm all ears.

I know that this is a Pandora’s box, but if you could just state your opinion and a quick reasoning . (to include cost effectiveness) that would be awesome.

... and to set the record straight, I do alot of work on my jeep and I've messed with everything shy of the tranny and engine.

1989 4.2 258 weber carb. / AX-15 / NP-231 / 6 inch lift on 33s.

Thanks in advance gents!

**zeus87gn** · 02-04-2009, 04:19 PM

Have the 258 rebuilt by a pro and use some good rings. Punch the cylinders and get new pistons if it's needed. The 4.2 is a fabulous motor it has to be built correctly. Do the 4.0l head conversion, keep the carb (for ease of repair and tunability) and enjoy your new found power and mileage!

mattman320 · 02-04-2009, 05:37 PM

4.3 chevy V6 can't go wrong. more power and mileage than either Jeep engine, not to mention they actually amke aftermarket parts (like superchargers and stuff) for it, you could go V8 but IMO stay away bad mileage and loots extra weight then you have to move radiator blah blah blah just gets to be to much most of the time. 0.02

**kkchevy3** · 02-04-2009, 05:42 PM

you have the base parts for a 4.6 stroker find a 4.0 block and have it rebuilt with ur 4.2 crank and rods maybe something like this
~ Jeep 4.2L 3.895" stroke crank
~ Jeep 4.2L 5.875" rods
~ Keith-Black Silvolite UEM-2229 +0.030" bore pistons
~ Increase piston dish volume to 30cc
8.8:1 CR
~ Crane #750501 192/204 degree camshaft
~ Ported HO 1.91"/1.50" cylinder head
~ Mill block deck 0.035"
~ Mopar Performance 0.043" head gasket
~ 0.058" quench height
~ 2.25" exhaust
~ Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines
~ 231hp @ 4400rpm, 327lbft @ 2000rpm
theres alot of info on this site http://www.ajeepthing.com/stroker-motor.html im currently building a 4.6 stroker and will be swapping the motors in a couple of weeks.

hillie4life · 02-04-2009, 06:04 PM

Thanks for the advice so far guys, I really appreciate it. Since I need to decide soon I really need the input!

**shaggyjim** · 02-04-2009, 07:09 PM

I love the Idea of the stroker and its what I'm going to build in the fall, however there is a lot of thought that needs to given to it. It not just a grab some parts and slap them together engine build. Check this site out aswell http://www.jeepstrokers.com/forum/ If you go with the stroker then I think you would be happy, and if not I would say rebuild your 4.2 short block and slap the 4.0l H.O. head on it. The 4.0l conversion is good for 40 hp I'm told. You can find the 4.0l heads rebuilt with the water jackets welded shut on ebay for about $500...

yjcrawlr · 02-04-2009, 09:25 PM

I just swapped in the 4.0 HO from a 95 cherokee. The expense was much less than rebuilding a 4.2. This is the 4.0 dropped in my 90 that had the 4.2.. It should be up and running by the weekend so I can tell you if it is worth the work. The swap happened last night.

wendell · 02-04-2009, 09:39 PM

I would stick with the 258, why give up cubes. You can put a 4.0 head on it for better flow and still have the cubes. I bulit my 258 with a a holley TA 470 4 barrel, offy intake, comp cam and header. All those parts were still cheaper than the mopar efi kit and it runs better than a 4.0 in my opinion. This summer going to swap on a 4.0 head and rollor rockers and have one mean 258. It's a power house now. The 4.0 is an excellent engine, but giving up cubes when you don't have to is going backwards. Also you wont have all those sensors to worry about, you still keep the engine simple and easy to work on.

yjcrawlr · 02-04-2009, 09:44 PM

.2 cubes I will give up for 50 hp. Stock 4.2 is only around 140 hp. I know I drove one for the last few years. The 4.2 was great at luggin up hills but ran out of hp on the highway.

**kkchevy3** · 02-04-2009, 09:47 PM

yjcrawler why dont you move ur airfilter over so its not sucking all the hotish air comming through the rad. who knows if it would make any difference

yjcrawlr · 02-04-2009, 09:52 PM

This is just to keep the crap out of my throttle body, nothing is clamped down or even finished. I took the old intake off my carb and made this one for mock up.. Actually there is a air duct for the stock air box in the grill next to the driver side headlight. I got it don't worry. This is where the engine was yesterday at 4:00.

**zeus87gn** · 02-05-2009, 06:58 AM

Quote:

Originally Posted by yjcrawlr

.2 cubes I will give up for 50 hp. Stock 4.2 is only around 140 hp. I know I drove one for the last few years. The 4.2 was great at luggin up hills but ran out of hp on the highway.

Interesting you say that. My 4.2 has never run out of power on the highway. I don't use 5th gear any more because it wines like a 2yr old that hasn't gotten his way, but when I did I couldn't use it below 70. All I ever had to do was push my foot down and it would go. Still running like a champ. I can't wait to get my 33's and 3.73's!

hillie4life · 02-05-2009, 11:58 AM

So no real proponents of going with a V8? nothing? really? to be honest I haven't seen too many v8s in yjs, but maybe I haven't looked hard enough. I just thought that some one would have had a comment on it.

**zeus87gn** · 02-05-2009, 12:17 PM

One day I would ike to do a V8 conversion, but it's not a priority for me as I have 4 kids to graduate from multiple schools and the old 4.2 runs so good I don't see the sense in spending the money. Maybe once I have some money burning a hole in my pocket, and the 6 I have now dies......

JMHO

hillie4life · 02-05-2009, 12:24 PM

Well thats the thing, my 4.2 is dead, I'm just trying to utilize this excuse to get some cool stuff done while i've got it.