4.7L Stroker For 99 XJ build

[Cosgray]

Cheers from Tucson, AZ

Alright. After lurking in the shadows for about a year, sifting through the forums, I have decided to emerge into the light to begin my stroker build.

This past Saturday, I pulled a 4.0 from a 97 zj at a junkyard for $200. The zj on the lot showed no signs as to why it would be at the junkyard (no body damage, visable motor damage, visable tranny damage, or any other damage for that matter), so I was slightly skeptical about the motor. On the plus side, someone had removed it recently to replace the rear freeze plugs, and no E12 bolts in sight, so removal was easy.

Took her home, and to my surprise, The motor was freshly re-built. Brand new seals, bearings, lifters, rockers, springs, and a heavy duty camshaft. also, the previous owner appears to have done a port and polish on the head, but further cleaning is still needed to be certain. But a lot of my work has been taken off of my plate.

Also upon dissembling the motor, I discovered why it was on the lot at the junkyard. bad Carbon build up on cylinders 1&2, with minor build upon cylinder 3, as well as bad/warped/whatever piston rings on cylinders 5&6.

so essentially, I'm in a really good place for my 4.7 Stroker.

However, I do have some questions that I was unable to find the answers for. I know I want a 4.7, and that means a 4.2L Crankshaft, as well as a +0.060 overbore on the cylinders. However, I am uncertain of what else is needed to be machined to the block, and, if I'm wrong, the head has not been ported, what would I need to tell the machinist when I go to get work done. Is there a definative list of what exactly the machinist needs to do, like a job sheet/blueprint (I'm a CAD designer, with experience in machining, but none when it comes to machining engines).

any extra information would be appreciated.

[SkylinesSuck]

I wouldn't trust any "work" previously done to the motor. Everything should be redone and redone. A bone stock crusty motor with factory gaskets would be my fave.

Why do you say you want a 4.7L?

[Cosgray]

I'm looking for throttle response mainly. I'm sure many other people have been in the position I'm in, where nearly nothing improves it. I want to be able to touch the throttle and have the power I need then, not 2 seconds later. I plan on crawling my jeep, as well as using it for my company's billboard. My brother, dad and me are starting a design and fabrication company, focusing on badass bumpers like what I have, and being able to take it to any of the jeep events and not have to worry about a lack of power. I would like to put a supercharger on it at some point and the dynamic compression ratio of the 4.7 I'm currently figuring will work best with the supercharger I have in mind.

[SkylinesSuck]

Sorry, I should have been more specific. Why a 4.7 as opposed to a 4.6? The difference will be academic. You won't notice a real world difference except when it comes time to rebuild/rebore your engine and you can't anymore.

[Cosgray]

Aside from what I already mentioned, I don't plan on rebuilding this one when its dead. My end goal is to do a full 4bt/6bt swap. But not for many years. I want something I can enjoy until then.

[Cosgray]

Plus from what I've seen ill be spending roughly the same amount whether i go 4.6 or 4.7. If someone can show me that ill save more than 200 bucks, and have close to no performance difference, then I'm game to change my plans. But from what I've seen I'm dead-set on a 4.7. That's been my plan for about 6 months now.

[jsawduste]

Someone correct me but isn't the ZJ block engine mounts different than an XJ ?

All this nonsense on 4.7 being any better or different is purely nonsense. That .1 is invisible.

[Cosgray]

Zj and xj 4.0's are interchangeable. At least that's what every site I looked at. Only the wj 4.0 doesn't work

[nicpaige]

When you are done with this stroker and want to sell it you will wish you went 4.6 @+.030" over. If you have no problem with chucking the block and not getting any money out of it then by all means go +.060". I can think of a few more reasons to stay at .030" and none for going .060" other than your cylinders require it for a proper clean up.

[Cosgray]

This jeep is my forever project. Not going to sell it. My parents bought it when I was a kid, I grew up in it. And now its mine. Too much sentimental value to sell. Ill be building this motor, as well as building the original for a back up once the swap is complete. So 2 motors for no longer than 5 years until I can do my 4bt/6bt swap. I think ill be fine.

[gradon]

I wish I had gone 4.7l instead of 4.6l(was the same price). If you ever "have to" re-bore your 4.7l, you can always order +.080" or +.090" custom pistons(the bores can take it).

[Russ Pottenger]

I wish I had gone 4.7l instead of 4.6l(was the same price). If you ever "have to" re-bore your 4.7l, you can always order +.080" or +.090" custom pistons(the bores can take it).

X2

95% of the engines that leave my shop do so with a 3.935 bore.
I stock and have 3.970 Bore Pistons on the shelf. That's typically what my race engines are running for bore size.
Also keep in mind replacement blocks can be fetched for around $200.00

[SkylinesSuck]

Do you think there is a power difference between the two bores Russ?

[Russ Pottenger]

Do you think there is a power difference between the two bores Russ?

About 4 to 5 HP Chris.

[Cosgray]

Thanks, gradon for the input.

Russ, you work in a machine shop? Is there anything I should provide the machine shop I go to besides the block and head? I'm not quite ready to take it there, still have to clean up the head a little bit and check for cracks, block is clean and good, but I want to make sure I have covered all my bases when I take it there. I plan on assembling the motor myself, I want the motor to be 90% me.