Jeep Strokers

My research last fall led me to this forum. My thanks to all who contribute here. Your knowledge and expertise is invaluable.

My goal was a stroker that would run on low octane pump gas, 87 here on the East coast. Here is my parts list, the majority purchased from Russ Pottenger.

2001 Jeep Cherokee XJ: Engine rebuilt to 4.6 Stroker

Comp Cams # 163-301-5
Bore + .030”
Racetec Pistons 26cc
2003 Jeep Grand Cherokee 331 TUPY Cylinder Head
Intake valves 2.000
Exhaust 1.550
OEM Rockers
New Push Rods
New Lifters
New Valve Springs/Keepers
Scat 4.2 l Crankshaft (3.895)
New Harmonic Balancer
BBK 62mm Throttle Body
24 LB EV-6 Bosch Injectors
Champion 3412 Spark plugs (2 steps colder than stock)
OEM Water Pump
Felpro Head Gasket(.040) & Bolts
Felpro Valve Cover Gasket
Mahle Manifolds Gasket (matches oem metal style which will cut fingers)
Brass Freeze Plugs

Design is 8.11:1 DCR, 9.29:1 SCR according to the S/D Compression Ratio Calculator on this site.

I now have my first 100 miles on the engine using Comp Cams break-in 10w30 break-in oil. It's running smoothly and handles hard acceleration on 87 octane with no pinging. Outside of the new parts, the only other modification was to port-match the intake manifold. I had a local shop set my cps with the Chrysler tool.

I am not an off-roader although I believe this set-up would work well off-road. It's primarily my daily driver and used for light towing, up to 2500 pounds or so. I added a transmission cooler several years ago.

You folks answered a lot of my questions and Russ filled in the blanks. I hope this post will contribute to the next builder attempting to get similar results.

Doug

Glad you're enjoying your new stroker Doug. Long may it continue.

Was MY pleasure to be part of your project Doug.

Dino’s stroker build is a good example that with the correct recipe of good parts and machine work these strokers will reward you with many trouble free miles and making your Jeep a helluva lot more fun to drive.

Yup, Russ sold me the parts to build a bad little 284 CI inline six engine that kicks butt on 87 octane gas. I even advanced my timing when I mounted my crankshaft sensor on my TF-999 transmission. It’s an awesome engine, Thanks to Russ.



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I’m running 31’s and 273 gears and it will launch and accelerate quickly, I smoke a lot of cars off the line at traffic lights.

I can drive on the freeway, and pass when I want when the traffic is moving at 60-70 MPH.

This is a completely different Jeep to drive now. I replaced the steering gear with a new one for a H1, along with a new Borgenson intermediate shaft and a new Wolfe lower column bearing, now it drives and steers like a new Jeep. I know because I have one.

The CJ-7 is faster than the EcoDiesel…I know, I have run them both at the drag strip.

What did each of them do on the strip? Seeing those drag times seems interesting if nothing else.

Glad to hear your engine is working well. When I have trouble with something it's nice to know someone else got it done correctly haha. At least it's possible!

I was incorrect when I stated the stroker 4.7 in the CJ-7 was faster, it is quicker, but with less MPH.

My all stock 2020 EcoDiesel JLU ran a 10.53 at 70 MPH half track (1/8 mile).

My 1985 CJ-7 with the 4.7 stroker ran a 10.22 at 66 MPH at the same drag strip, half track.

With my 258 in the CJ-7 it ran 12.4 at 53 MPH half track.

The Diesel is really slow off the line, due to turbo lag, even when I foot break it to build boost before launch, but it runs a better MPH, indicating it is making more power. It has 373 gears with a LSD in the rear, and an 8 speed automatic transmission.

The CJ-7 has a TF-999 3 speed automatic transmission, and 273 gears with an open differential in the AMC-20, and it will spin if I launch at full throttle. I had to launch at about half throttle, and then ease into WOT to prevent it from spinning off the line. I believe it would have been running in the 9’s if I could have launched at WOT without spinning.

I have a Ford 8.8 rear out of an Explorer with 373’s and a LSD. I am going to narrow the long side to match short side and run two short axles, for a WMS width of about 57”, so it will be close to the 56” WMS width of the AMC-20. I’m pretty sure it will run in the 8’s half track with 373 gears and a tight LSD. I should be able to launch at WOT without spinning the 31’s I’m running.

According to my calculations, your 4.7 stroker is making almost double the amount of power of your original 258. Not bad eh?

Yes, I came up with the same results using online calculators. I’m thinking about going to some 1.7 RR’s and a 68mm throttle body. I am currently running stock Mopar rockers and a BBK 62mm throttle body. I figure it will all work with the 373 gears when I swap to the 8.8 rear.

A short update on the stroker that started this thread:

I have 2557 miles on the build, over 1700 traveling to and around the Catskill region of NY from NC over two weeks. The highway mileage was between 20 and 21 mpg. The local, and very hilly driving was 17-18 mpg. My low tank was 17.15 mpg and my best was 20.98 mpg. These numbers are comparable to my 4.0 which was 16 mpg around town and a best of 22 mpg on the highway. I'm on my second oil change since break-in using Valvoline VR-1 Racing conventional 10w30 which has zddp. I don't think it's available in CA. Performance for my street-driven Cherokee XJ is improved. Long high-speed upgrades on the highway used to defeat my cruise control which couldn't maintain speed. That's no problem now. I am impressed with its tractability without having to downshift. I used only 87 octane.

The only issue has been three misfire codes two on cylinder 2 and 1 on cylinder 5. None was noticeable so I was surprised with the MIL. The scanner showed each had self-cleared. This was unlike the typical cylinder 3 misfire that my 4.0 would get on a hot day, always resulting in a rough idle.

I am comfortable recommending this recipe to anyone wanting the economy of regular gas with noticeable performance gain.

Married Man wrote: ↑July 22nd, 2021, 11:18 amThis was unlike the typical cylinder 3 misfire that my 4.0 would get on a hot day, always resulting in a rough idle.

That cylinder 3 misfire would be caused by heat soaking of the no.3 injector and there was a TSB with a fix for it.
Yours sounds more ignition related.

Married Man wrote: ↑July 22nd, 2021, 11:18 am A short update on the stroker that started this thread:

I have 2557 miles on the build, over 1700 traveling to and around the Catskill region of NY from NC over two weeks. The highway mileage was between 20 and 21 mpg. The local, and very hilly driving was 17-18 mpg. My low tank was 17.15 mpg and my best was 20.98 mpg. These numbers are comparable to my 4.0 which was 16 mpg around town and a best of 22 mpg on the highway. I'm on my second oil change since break-in using Valvoline VR-1 Racing conventional 10w30 which has zddp.

I am comfortable recommending this recipe to anyone wanting the economy of regular gas with noticeable performance gain.

That’s great fuel economy, I wish mine got 20 MPG. Mine gets 15, but the fun factor driving it is off the scale. I used 15-40 Shell Rotella when I changed my oil after the break in oil was changed, around 300 miles. I am coming up on my first oil change after about 5K miles on the engine. I’m thinking about going with 10/30 this time. My oil pressure is 60-65 on the highway, and 20+ at idle, even when it’s very hot it has never been less that 20 at idle. I believe I could go with 10/30 and still have good oil pressure, and maybe pick up some better fuel economy.

Either way, this engine rocks on 87 octane gasoline.

My oil pressure is steady at 40-45 psi under load and drops to 15-20 at idle. My engine temp, with a 195 thermostat never goes above 205 or so. I was stuck in a crash-caused traffic jam(5 miles in 1 hour) at 90 degrees and the temp barely broke 200. So far, so good.

Doug