4.2 & 4.7?

Jeep made a 4.2 and 4.7 liter I6? http://jeephorizons.com/tech/#Stock under stock specifications. is this web site bogus or have i just not been paying enough attention?

The 4.7 is a V8.

4Banger said:

The 4.7 is a V8.

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also... neither was available in the XJ line. 4.2 IIRC showed up in YJ's while the 4.7 showed up in ZJ's or WJ's (don't remember which)

You may see 4.7L's talked about on the forum associated with XJ's. Normally that means that somebody took a 4.0L and made a stroker motor out of it.

old_man said:

You may see 4.7L's talked about on the forum associated with XJ's. Normally that means that somebody took a 4.0L and made a stroker motor out of it.

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True, but here we're talking about the 4.7 in relation to a page that lists it as a "1999 Jeep 4.7 Liter engine" Also aren't there 4.2 strokers out there as well?

A stroker is made by using the 4.0L block and putting in the 4.2L crank and rods.

The 4.2 is the classic SJ/CJ/YJ 258ci AMC six. Smaller bore, but longer stroke, than the 4.0L six. Good engines with typically poor carburation and emissions controls (pre-injection era AMC).

The factory 4.7 is sometimes called the Mexican stroker, an early 80's vintage factory experiment with 4.2 crank and an almost 4.0L bore, (reported to be) assembled to provide adequate power at the high altitude of Mexico City. The pistons were rough full circle dished castings with fairly low compression and none of the quench attributes of the combined 4.0L piston and head chamber. A few appear to have made it into US vehicles in J-trucks and SJ Waggoners (another Jeep, whatever's in the parts bin, thing). They are actually more like 4.5L in displacement, and they are very rough compared to a modern 4.0L stroked with the 258 crank (an example of what 20 years can do).

Edit: It appears the web site link knows nothing about the AMC six varients (232/258/262) and the 4.7L link is for the V8 (and they forget AMC Jeep also used a Buick 225 V6 for a few years in CJ's).

Hmm, didn't know about the factory 4.7 l6.
I really like this site more and more.
Each day I learn something new.

Ed A. Stevens said:

The factory 4.7 is sometimes called the Mexican stroker, an early 80's vintage factory experiment with 4.2 crank and an almost 4.0L bore, (reported to be) assembled to provide adequate power at the high altitude of Mexico City. The pistons were rough full circle dished castings with fairly low compression and none of the quench attributes of the combined 4.0L piston and head chamber. A few appear to have made it into US vehicles in J-trucks and SJ Waggoners (another Jeep, whatever's in the parts bin, thing). They are actually more like 4.5L in displacement, and they are very rough compared to a modern 4.0L stroked with the 258 crank (an example of what 20 years can do).

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That would be a simple bore job, not a stroker, as it uses the original stroke crank. The displacement is closer to the 4.5, not 4.7. People building the 4.2 sometimes bore to 4.0 dimensions and use the 4.0 head, resulting in the 4.5 w/ significantly more power when combined with the modern fuel inj.

explorer said:

That would be a simple bore job, not a stroker, as it uses the original stroke crank. The displacement is closer to the 4.5, not 4.7. People building the 4.2 sometimes bore to 4.0 dimensions and use the 4.0 head, resulting in the 4.5 w/ significantly more power when combined with the modern fuel inj.

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No, because not many people base the engine on the 4.2L block. The so-called "stroker" engine is made up using a 4.0L block and a 4.2L crank. At stock 4.0L bore it is 4.5 liters, but at 0.030 over (which is probably the minimum you can get away with when rebuilding a block) it comes to 4.6 liters, and if you bore it 0.060 over it's 4.7 liters.

For 4Banger -- there was never a 4.7 liter I6 from the factory in the U.S. As Ed Stevens noted, the reference to a 1999 4.7L engine is to the then-new 4.7L V8 that was introduced in the 1999 Grand Cherokee.

The Mexican 4.7L engine was not used in XJs, it was used prior to the XJ in CJs built and sold in Mexico. They needed the additional volume to make up for the power lost at Mexico City's altitude. Although a very few examples may have escaped to north of the border (I knew of one that was scrapped in Canada before the owner knew what he had), they were never sold in the U.S. What was available in the U.S. was either 4.2 liters (older AMC vehicles and the YJ Wrangler with carburetor thru 1990), or 4.0 liters (introduced in the XJ and MJ in 1987 and to the Wrangler line in 1991.

Eagle said:

No, because not many people base the engine on the 4.2L block. The so-called "stroker" engine is made up using a 4.0L block and a 4.2L crank. At stock 4.0L bore it is 4.5 liters, but at 0.030 over (which is probably the minimum you can get away with when rebuilding a block) it comes to 4.6 liters, and if you bore it 0.060 over it's 4.7 liters.

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Let me understand this. Your saying that this "mexican" block was a 4.0 block before the 4.0 was officially introduced? Im confused. If it a 4.2 with a 4.2 crank, and overbored to stock 4.0 bore then its a 4.5 but not technically what I would call a "stroker".

explorer said:

Let me understand this. Your saying that this "mexican" block was a 4.0 block before the 4.0 was officially introduced? Im confused. If it a 4.2 with a 4.2 crank, and overbored to stock 4.0 bore then its a 4.5 but not technically what I would call a "stroker".

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It was, essentially, a 4.0L block -- before the 4.0L engine existed. It was a 4.2L (258) block built in a Mexican plant, cast with extra-thick cylinder walls to allow it to be punched out to 4.5 liters in stock form. As Ed posted, it was crude, the pistons were slugs made by a Mexican company and when a former member of the Yahoo Strokers e-Group (now deceased) bought a replacement to study as a possible piston for use in stroker 4.0L engines, he reported it was so rough it almost looked like it was hand made.

This engine has nothing to do with anything offered in the U.S. It is just another of the quirks or anomolies from AMC days.

So what was it, 4.0 or 4.2 to start with. If it started as a 4.2 block as you say, then was fitted with .030" over pistons, how is it a stroker. In my book, a stroker is a block/crank combination that has a longer stroke than original. So, a 4.0 block fitted with a crank from a 4.2, with a longer stroke is a stroker. A 4.2 block and crank fitted with 4.0 pistons with a larger bore is not. Semantics I guess, but I hold my position. Any old Chevy engine that displaces 383ci does not necessarily make it a stroker. The fact that its stroke length was increased from standard does.

It started life as a 4.5 liter engine sold only in Mexico. It's called a "Mexican stroker" because we don't have a better way to describe it. It was neither a 4.2L nor a 4.0L -- it was a 4.5L from the factory.

Gotcha, just had to clarify what the term stroker "usually" refers to.