DeereHunter

I had no clue, I thought 242 was the C.I.
My biggest fear is just screwing up, and wasting a ton of money.
Hopefully with the advice you've given me things will go ok.

Thanks again for the help

dave1123

No problem. I do what I can to help others. I've been working on cars and trucks for over 50 years. Drag cars included. I'm a toolmaker and have made special parts for cars, trucks, boats and motorcycles. I enjoyed every minute of it! Oh, yeah! I forgot snowmobiles. Most of what I did was before electronics got involved.

DieselD

The 4.0L is 242 cubic inches.

There IS a 242 transfer case though. Lol

dave1123

Sorry about that, Diesel D. I can do linear metric conversion well, but not volume. I thought 4.0 was 244 cu.in. (61/liter)

DieselD

It might be and its just called 242ci. I dunno. I've just always seen "L6 4.0L 242ci"


Where'd my 2ci of motor go!?!? Lol

DieselD

Maybe they're not truely 4.0L?

3.97 and 3.98 x 61 comes out to roughly 242... hmmm.

dave1123

I guess we're picking nits here. I didn't want to get into a ****-fight about it. I only know the engine size limit for Can-Am racing was 5 liters and Ford was running the 305. Chevy built the 302 to compete against Buddy Moore's Mustangs. (circa 1967's Z28)

DieselD

No fighting. Just discussion. Lol

Since you said something I was just curious where they got their numbers.

It either IS a 4.0L and is technically 244ci or IS 242ci and techically ISN'T 4.0L that is if that equation is right. Which I wouldn't know anything about.

dave1123

I guess to know for sure, you'd have to check bore and stroke and do the math. I think Jeep just calls it a 4.0 to keep it simple. Just like Dodge calling their engine a Hemi when it technically isn't! The last actual Hemi Chrysler ever built was the 1958 392. Oh! Wait! Wasn't the 426 a true Hemi? They just twisted the exhaust valve angle.

Metmknice

Actually, there are lots of vehicles and aftermarket heads that have the hemisphereical shape.
Lots of engine sizes are rounded. Obviously, 3.98 is close enough to 4.0L
There are other engines with specific dspl. that are called other. For example..
Ford 302, if you do the math is 4.9x, The Gm LS1 "5.7" is actually 347ci etc etc.

dave1123

Getting back to this guy's 4.0, I'd say the best thing to do is replace the motor. THEN, if he wants, he can keep or sell the good parts.

DeereHunter

You guys have the knowledge of engines I wish I did.
For my own curiosity, what IS a 'true' hemi? What makes it a hemi?
I have a great lead on a '01 XJ motor. Around 150k miles, apparently running good. I imagine it's worth the time to rebuild it while it's out of the car though. Expecially with that mileage.

dave1123

Basically, a Hemi has a perfectly spherically curved cylinder head chamber. This requires the valves to be directly opposed from one another with the spark plug in between. At high RPMs the cylinder "breathes" rapidly with little turbulance. At low RPMs, there is too little turbulance to cause a clean burn or complete scavaging of spent gasses. In the mid to late 50's Chysler built their Hemi V8s and they required 2 rocker shafts and long rockers to actuate the valves. The spark plugs were in long sealed tubes in the center of the valve covers. The complete engines weighed 700 lbs. The blocks were thick and could be bored 1/8" oversize with out problems. These engine were replaced by the polyspherical heads by clanging the placement of the exhaust valve, basically twisting the chamber like a soft ball. They didn't work out well.

Today, most engines have a wedge shaped chamber with both valves side-by-side.

The hemi heads are still used in racing by many manufacturers like Honda and Ferrari in Formula 1. Most use dual overhead camshafts.

I feel like I'm teaching a history class!

As far as your XJ motor is concerned, I would just regrind the valves and put it back together. You can check compression and the bearings, but 150K on a 4.0 isn't a lot.

DeereHunter

Finally found a donor motor! 1996 cherokee, it has a lower end knock, 196k on the clock, still running though, I think it will serve my purpose though!

dave1123

FIX THE KNOCK before you put it in, by ALL means!