New Stroker Build

[Kahlis]

Good day everyone!

Got a wild hair up my a$$ to build a stroker for my '96 ZJ. After reading a couple posts here and cherokeeforums.com (including CyberShot's 4.7 stroker build), I decided why not! I consider myself a rather decent backyard mechanic; been working on cars since a boy with my Father, and every car I've owned as an adult. My last big project was an '81 Camaro Z28, but the longblock came rebuilt so all I had to do was bolt on the top end and accessories. All that to say, I can do the work, but the more I research I do the more confused I get. A little help from those who have done it would be a big help.

The '91 242 block is getting cleaned/shot and bored .40 over. I thought about going the full .60 over, but this is a budget build and I don't want to drop top dollar gear to make it a full 4.7L. To help move things along, I ordered a 258 crank from an '87 Wrangler. Apart from a rebuild kit, I have most of major components taken care of. I'm sure I'll have a string of questions as I move forward, so I appreciate any/all insight you guys can give me.

[gradon]

I recommend going .060" over. It won't cost anymore.

[Kahlis]

How much high performance goodies will be required going .60 over versus .40? Already plan on a decent cam, but I am unsure if I'll need any additional upgrades.

[jsawduste]

Do more research. Plenty of information out there on stroker builds.

[gradon]

You're gonna need 24# injectors@49psi(assuming you have the same fuel system as my 96 xj), a bigger bore throttle body(65-70mm), bigger diameter intake, and at least a 2.5" exhaust. Then you should find someone local who can re-flash your stock pcm with a dyno-tune.

[Kahlis]

Ok. That'll at least point me in the right direction. I'm sure our fuel system is similar, same year anyway, but I'll be sure to buy the bigger injectors. I'll pull the computer from my donor Jeep and get it flashed in advance.

[SilverXJ]

The 91 donor Jeep?

[gradon]

Most likely it's gonna have to be a 96 pcm. Your stock pcm will be able to adapt at the start. I just recommend getting it dyno-tuned at a reputable shop in your area to get the most out of your particular build. It'll cost $400-600.

[Kahlis]

'96 donor. The engine came from a '91.

$400!?

[gradon]

Custom dyno-tuning takes some time and costs $. A similar or higher cost alternative is to buy a wide-band o2 with data logging from obd2 data(rpms, map, timing, fuel trims), a hand-held programmer, and then send a tuner your data, then they'll email you a tune to upload into your programmer.

[Kahlis]

After some digging around on other member's posts, I found the page to alleviate some headache. Thanks to dinosavva for simplifying things. http://www.jeep4.0performance.4mg.com/stroker.html

From this site, it would appear I'm crossing between the Poor Man's and the Medium Buck (engine is already bored .60 over). However, it's not in my budget to buy an Edelbrock head, for as much as I'd love to, and considering cutting some cost by keeping the cam stock. Although, the cam is only $166 from Jegs; perhaps do-able. In addition to a rebuild kit (around $400 or so) I plan to get Bulltear pistons - http://www.bulltear.com/catalog/product ... cts_id=242

Question - can I run the Medium Buck build with the factory head and cam? Obviously an aftermarket head a/o cam is bolt on performance for any application, but I worry if keeping those parts stock may not jive well. Have I answered my own question,... ?

Here are the specs between the two build:

- 4.6L Modified “poor man’s stroker
Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.020" bore pistons, compression height 1.380", dish volume 26cc
9.25:1 CR
Stock 4.0 camshaft
DIY ported HO 1.91"/1.50" 57cc cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Ford 24lb/hr injectors for '87-'95 engines, Accel 24lb/hr injectors for '96-'04 engines, '98 Chevy LS1 25.2lb/hr injectors for '05-'06 engines
249hp @ 4900rpm, 303lbft @ 3500rpm ('87-'95 camshaft)
245hp @ 4700rpm, 315lbft @ 3000rpm ('96-'04 camshaft)

- 4.7L medium-buck stroker
Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.060" bore pistons, compression height 1.380", dish volume 15cc
10.2:1 CR
CompCams 68-235-4 210/218 degree camshaft
Russ Pottenger ported Edelbrock 60cc aluminum cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Flometrics F&B 68mm billet TB
Accel 30lb/hr injectors for '87-'95 engines, Accel 26lb/hr injectors for '96-'04 engines, '01-'02 Chevy LS1/LS6 28.6lb/hr injectors for '05-'06 engines
290hp @ 5100rpm, 340lbft @ 3700rpm

[Cheromaniac]

After some digging around on other member's posts, I found the page to alleviate some headache. Thanks to dinosavva for simplifying things. http://www.jeep4.0performance.4mg.com/stroker.html

Well, you've found me over here too.
Since the donor engine is going into your '96 ZJ and I assume you'll be reusing the '96 ZJ electronic controls, the simplest build you could do is the modified poor man's stroker. The +0.020" overbore isn't set in stone so you could go higher. A 0.020" overbore will yield a displacement of 4563cc, while a 0.060" overbore will yield a displacement of 4657cc (94cc more). This is the potential spec of your poor man's stroker:

4.7L Modified “poor man’s stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom forged +0.060" bore pistons, compression height 1.380", dish volume 28cc
9.25:1 CR
Stock '96 camshaft
Stock #0630 cylinder head (57cc chamber)
Mopar/Victor 0.043" head gasket
0.043" quench height
Dodge Neon EV6 injectors

Power output will be ~230hp with a stock unported head and ~250hp if the head is professionally ported, with torque around 315-320lbft.

[Kahlis]

http://www.bulltear.com/catalog/product ... cts_id=242

$475 the price for all six pistons? I nearly confirmed the order until I second guessed.

I left a vmail and email asking - has anyone else bought their pistons?

[Kahlis]

Pistons ordered! Now to sit patiently for three weeks!

[amceaglesx4]

I just couldn't see the justification of $400+ for pistons myself. I'm going with the 4.2 rods and 677p pistons 60 over. Decking the block was way cheaper.