Jeep Strokers

I have a 99 TJ 4.0 I want to build a 4.6 Stroker. Why the wife ask. Because.
I've been only toying with the idea for a few weeks but that means my brain has been working on it full time. I can rebuild any stock engine, but modifying is a different animal. I currently have a good running 4.0 in my jeep. I have a junk yard 97 4.0 i believe its out of a xj and i have a complete 87 4.2L. Ive seen all kinds of opinions on what works best, but can some one point me to know working builds. I would prefer 87 octane, but would also like to possibly duplicate the golden 4.6 stroker if anyone has a link to that parts breakdown. Thanks in advance.

Hi, everyone wants more power out of their 4.0 because 190hp doesn't cut it these days, and more torque makes highway cruising effortless with the bonus of better gas mileage.
You'll find the link to my stroker recipes in my signature. Naturally the most popular are the 4.6/4.7L set ups. The 4.6L low buck recipe suits most people's needs and is probably the one that's been most replicated (some with slight variations). Your parts list would be:

4.6L low-buck stroker

Jeep 4.2L 3.895" stroke crank (handily you can source that from your 4.2)
Jeep 4.0L 6.125" rods
Custom forged +0.030" bore pistons, compression height 1.380", dish volume 18cc (Russ Pottenger can supply those to his spec)
9.6:1 CR
CompCams 68-231-4 206/214 degree camshaft
Russ Pottenger ported HO 2.00"/1.55" 62cc cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Ford 24lb/hr injectors for '96-'04 engines
268hp @ 4900rpm, 326lbft @ 3500rpm

Golen's engines are good but they've become eye-wateringly expensive these days and you can build your own at far less cost.
The poor man's recipes are OK if you have a stock camshaft that's still in perfect condition but by now, most donor engines are 20+ years old and since you'd probably want a new camshaft anyway, you might as well add more performance.
Keep in mind that in order to achieve the power numbers quoted above, you'll also need supporting mods such as a higher-flowing cold air intake, 62mm throttle body (minimum), header (eBay would be fine), and 2.5" exhaust.
The stock cooling system is usually up to the job but I'd recommend you get a new 2-core aluminum radiator for better heat dissipation.

Thanks for the info. Here’s my current thoughts. 4.0 rods with a .30 over 4.2 piston. Deck block to around 9 thousands. I’m still not sure in which can to go with yet. Also I’m getting conflicting stories on port and polishing head. Hot rod shops around here are saying it’s not necessary since I’m after torque and not horsepower. Thoughts????

As Cheromaniac suggested, if you use 4.0 rods with the stroker 3.895 (4.2L) crank, you need a piston with 4.0 (std, +.030, etc) bore but a shorter compression height like Russ’ custom so the piston isn’t way out of the hole at TDC. Or you can use shorter 4.2 L rods and a 4.0 piston with the stock compression height-this was the original poor man’s stroker. I also used Russ’ pistons and other parts with 4.0 length rods but both combinations work. TJBUD

ande1879 wrote: ↑March 3rd, 2023, 2:58 pm I’m getting conflicting stories on port and polishing head. Hot rod shops around here are saying it’s not necessary since I’m after torque and not horsepower. Thoughts????

Cylinder head port dimensions are a small part of the horsepower, torque & RPM ratio. No matter how far the Jeep ports are modified, the engine will always produce a rather high torque value compared to HP. Only max effort builds, with larger ID valve seats and larger OD valves, will truly benefit from serious material removal and reshaping of the ports.
While there are a few other factors in play, this is primarily due to the available intake valve curtain area in the combustion chamber. If you are keeping the stock valves and valve seats, the stock curtain area will be the limiting factor regardless of the cross section of the ports. What a lot of folks do, which is practical, is quickly run a 60 or 80 grit cartridge roll through each port to remove any casting flash or irregularities in the cast iron. Port matching the intake ports to the intake manifold is another simple practice that can help improve air flow by removing deviations in cross sectional area of the intake air charge.

Thanks for the info. That supports what I’m hearing.

TJBUD wrote: ↑March 3rd, 2023, 6:43 pm As Cheromaniac suggested, if you use 4.0 rods with the stroker 3.895 (4.2L) crank, you need a piston with 4.0 (std, +.030, etc) bore but a shorter compression height like Russ’ custom so the piston isn’t way out of the hole at TDC. Or you can use shorter 4.2 L rods and a 4.0 piston with the stock compression height-this was the original poor man’s stroker. I also used Russ’ pistons and other parts with 4.0 length rods but both combinations work. TJBUD

Thanks. This makes sense except the price tag on those pistons and rods are more than I’m looking to spend. The stock pistons are much more affordable and I already have 4.0 and 4.2 rods. So the question remains is decking the block a way to use the stock pistons .30 over. Decking here is cheap like $100

Picked up my doner 87 4.2 today.

The longer stroke 4.2L crank requires a shorter rod(from 4.2) or a shorter compression height(<4.0 stock) piston. So if you want to use stock (std or +.030) 4.0 pistons you will have to use 4.2L rods, which many have done. You can deck the block if needed to achieve the desired deck clearance with that combination. TJBUD

Decking the block is something that needs to be determined after the crank/rod/piston combo is figured out.
IF going with "stock" parts the pistons MUST go with the block and the rods MUST go with the crank, about the biggest issue with this is the compression ratio, it goes UP! and high octane fuel is required.
If you want to use the long (4.0) rods and the long (258/4.2) crank you'll need special piston, there are several available.

That’s the route I believe I am going is 4.0 rods. I just haven’t nailed down what pistons yet? I’m open to suggestions. And I definitely want to do what is needed to keep compression low enough to run 89 octane

Here are my main 3 questions as of now

What pistons to use with 4.0 rods?

How much does the block need decked with stock 4.2 pistons .30 over?

What cam to keep head springs stock? I believe the 252 cam I’ve heard a lot about is no longer available.

A You can’t use 4.2 pistons in the 4.0 block-the 4.2 pistons diameter is too small (3.75”) for the 4.0 bore (3.875 std, 3.905 +.030)
B Here’s a good thread on piston challenges with the 4.2L crank and 4.0 pistons
viewtopic.php?t=6252
C In general, the max lift for stock springs is .450”. this is why Comp Cams No Springs Required cams like the 163-201-5 has 0.450 lift with the exact same duration as the 163-301-5 with .488/.507 lift which requires new springs. Here’s lots of 4.0 cams
https://www.angelfire.com/my/fan/Jeep4.0Camshafts.htm
TJBUD

B should read challenges with 4.0 rods

So your recommendation is to use the shorter 4.2 rods?