Updates
[Introduction] [Parts Selection] [Parts List] [Specifications] [Preparation] [Assembly] [Installation] [Results] [Updates] [FAQ's]100 miles: Checked the cooling system and it was free of air. The engine runs beautifully and it's a torque monster! Idle is smooth and is settling at 750rpm. The idle speed will occasionally drop to 600rpm for a second or two when I pull up to stop but only when the A/C is running. Engine oil temp. 187*F on the highway.
200 miles: Checked the plugs and the engine's still seems to be running lean so I raised the MAP voltage to 5.5v. Idle speed is steadier and doesn't drop as often.
350 miles: First tankful of gas averaged 18.1mpg. Not bad considering that the engine's still breaking in. Oil temp. down to 182*F and coolant temp. 205*F on the highway with A/C running and outside temp. 117*F. Engine also running slightly cooler in city driving.
600 miles: Gas mileage increased to 18.7mpg. Break-in period is over and the engine's loosening up nicely. Oil and filter changed. Since it's still mid-summer, I'm running Castrol 20W-50. Now I can extend the engine beyond 3000rpm and have some fun!
1150 miles: The engine starts faster and runs cooler with the MAP voltage set at 5.9v. Oil temp. not going beyond 210*F in slow traffic. Just installed my modified Mustang Cobra 65mm TB and it works beautifully. The whistling noise from the intake has gone and there are no more rpm drops with the A/C running.
1800 miles: Plugs look good, valvetrain noise is minimal, and the engine seems quieter. Oil level on dipstick hasn't moved since last oil change indicating that piston rings have seated nicely. There's a slight harmonic resonance at 4000rpm but beyond that, the stroker is more refined than my old 4.0L engine and it pulls hard all the way to the 5200rpm rev-limiter.
2300 miles: I finally got my junkyard 4-wire O2 sensor plugged into the header collector of my exhaust, installed my Autometer Phantom Air/Fuel Ratio Gauge, completed the wiring (very easy), and tested it. The gauge works great and the O2 sensor behaves as it should. To my surprise, the engine was running rich under all conditions except hard deceleration. I'd set the MAP adjuster voltage too high (duh!) and that explained why I was only getting 17-18mpg lately. I tweaked it and found that a setting of 5.35v was optimum. Intake manifold vacuum is a healthy 16"Hg at idle and 20"Hg when the throttle is snapped shut.
3000 miles: Second oil and filter change. This time, I'm using Mobil 1 0W-40 synthetic oil.
4500 miles: Fabricated and installed DIY Oil Catch Can
5000 miles: Gas mileage has improved to an average of 19.3mpg. MAP adjuster voltage reduced to 5.15v.
10000 miles: The engine has become smoother and stronger especially at higher rpm. Average fuel consumption is 19.9mpg. Emissions test showed an excellent 0.2% CO and 40ppm HC at idle.
20000 miles: Average fuel consumption improved to 20.2mpg.
25000 miles: Replaced old stock oil pump with a new Melling high volume unit and I'm very happy with the result.
27000 miles: Modified Borla header with 3.0" collector and had custom 3.0" downpipe made. Take a look here. I've found the holy grail with this stroker and I'm loving every minute of it! Who needs a V8 when you've got a straight six with V8-like grunt?
With this stroker configuration, the Jeep ran the 1/4 mile in 14.55 @ 95.2 in full street trim and 14.32 @ 96.2 with 170lb of weight reduction. Now that's kickin' ass!
34000 miles: Upgraded valvetrain with Yella Terra 1.6 ratio roller rockers and Crower chromemoly hardened pushrods. While I was installing the roller rockers to cure the increasingly loud valvetrain ticking noise (the original factory rockers had significant fulcrum wear), I discovered that the no.6 exhaust valve lifter wasn't preloading on the camshaft base circle when I torqued down the new rockers. The cause could only have been a worn or collapsed lifter so the head had to be removed to investigate further. The damage turned out to be even worse than I feared. In addition to a collapsed no.6 exhaust lifter, the no.6 intake lifter was badly cupped and the corresponding cam lobe was flattened. Aaaaaaaargh!
The engine was rebuilt using my original stock camshaft, new camshaft bearings, new lifters, the original stock valve springs/retainers, Crower pushrods, and Yella Terra roller rockers. In this configuration, the engine became a 4.6L version of the "poor man's" simple stroker featured on my stroker webpage. I reduced the MAP sensor input voltage from 5.15v to 5.10v to optimize the fuelling, and the engine was back up and running again with a near-silent valvetrain that'll hopefully stay that way for a very long time!
37000 miles: Reusing the original stock camshaft caused a slight loss of WOT performance compared to the Crane camshaft but the engine sounds sweeter and part throttle response is sharper. A run on the Dastek load type chassis dyno at MOCA Performance in Dubai yielded 250lbft @ 3750rpm at the rear wheels, but the run was aborted when the rev limiter cut in at 4500rpm due to a malfunctioning JET Stage 2 PCM.
39000 miles: With the JET PCM removed, the rev limiter was back to normal at 5200rpm. The engine also felt livelier so I did another a run on the same chassis dyno. The result was 198hp @ 4650rpm and 254lbft @ 3500rpm. Torque was increased from 1500-3800rpm with a whopping 9lbft gain at 2000rpm. The only downside was that the engine ran very rich above 4500rpm. With all that extra torque at low/medium rpm, the Jeep was more fun to drive and highway acceleration in 5th gear was quicker at all speeds.
41000 miles: Revised my homebrew FIPK by replacing the corrugated rubber pipe with a Simota 3" diameter smooth silicon pipe, and I moved it away from the throttle linkage to gain clearance. I also added 21" of 3" diameter PVC piping to route the intake around the brake master cylinder. The final length of pipe together with the air filter goes straight towards the driver's side headlamp housing instead of going diagonally, and this enabled me to simplify the heatshield.
45000 miles: A new run on the same Dastek chassis dyno with the revised intake yielded 200hp @ 4750rpm and 254lbft @ 3500rpm. HP and TQ were almost identical up to 4500rpm but thereafter, the revised intake allowed the engine to breathe more freely with a 6hp gain at 5000rpm.
54000 miles: I swapped the new style curved-runner intake manifold with power steering pump, PS pump mounting bracket, and tensioner pulley from a junkyard 2001 Jeep Cherokee into my Jeep. Installation was straightforward and the only modifications required to complete the job were lengthened wires to the IAT sensor, slight modification to the routing of vacuum lines, and a longer drivebelt. On the initial test drive the engine ran slightly lean but that was easily corrected by raising the MAP voltage to 5.20v. On the chassis dyno, the newer intake manifold yielded a torque gain of up to 5lbft from off idle to 4800rpm, with peak to peak gains of 2hp and 4lbft and the HP/TQ peaks coming at slightly lower rpm (see dyno chart below).
The latest 1/4 mile run of 14.63 @ 94.4 in full street trim was only marginally slower than the quickest time recorded when the Crane camshaft was in the engine. The Jeep does, however, feel quicker at part throttle with the stock camshaft and the hair-trigger throttle response makes it hugely entertaining to drive.
Ford Mustang Cobra 65mm Throttle Body
I bought an 86-93 Ford Mustang Cobra 65mm TB (F67U-BA) from e-bay for just 79USD, stripped it down to the bare bones, and modified it for use in my Jeep.
I also taper bored my Poweraid TB spacer to 65mm at the top and 62mm at the bottom (TB bore is 65mm, intake manifold plenum inlet is 62mm). With the larger TB and tapered spacer, throttle response is very aggressive indeed. The engine pulls smoothly from very low rpm with no bogs or hesitations. Job very well done!
Air/Fuel Ratio Gauge
I installed a 2-1/16" Autometer Phantom Air/Fuel Ratio Gauge (44USD from e-bay) in a pod that I mounted on the inside of the driver's side A-pillar. The gauge comes with a full set of installation instructions that make the job easy.
The red wire is connected to a 12v source from the ignition switch via a 5A fuse, the black wire is connected to ground, and the purple wire is connected to the signal wire going from the O2 sensor to the engine computer.
The lean range is 0.050v-0.249v (four red LED's), the stoich range is 0.250v-0.749v (ten yellow LED's), and the rich range is 0.750v-1.000v (six green LED's). At idle and light throttle cruise, the gauge should fluctuate across the stoich range. Under WOT acceleration, it should be two to three LED's inside the rich zone (0.80-0.85v), while under hard deceleration the gauge should show full lean or even go off the scale altogether.
Dyno Run
On a Dastek load dyno my 4.6L stroker engine produced 202hp @ 4700rpm & 258lbft @ 3400rpm (DIN) at the rear wheels, which translates into a healthy 248hp and 311lbft at the flywheel. With at least 230lbft available at the rear wheels from 1550rpm to 4550rpm, this engine's definitely a torquer.
The only performance-enhancing internal changes to the engine (apart from the increased displacement) were the higher compression ratio (9.25:1 instead of 8.8:1) and home ported cylinder head. Even the roller rockers are the same 1.6 ratio as the OEM stamped steel units. External bolt-on breathing enhancements and increased fuel delivery account for the rest of the 30% HP/TQ gain over a bone stock 4.0L engine.