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Topic Review (Newest First)
01-01-2014 05:47 PM
busterjeep Allow yourself 7K
350 chevy, 4 barell Carb, Auto 460l Tranny, Headers,4" Lift ,Tires & Wheels, Dual Custom Exhaust ,New motor mounts,, Electronics, Tranny Cooler. Speed shifter, Winch, On board Air. Plus Plus Plus..and I did a lot of my own work. 1994 YJ. FAST
08-04-2007 05:35 PM
jeeper95yj I have contemplated having a chevy smallblock 350 put in, but I love my straight six. I have heard to many mixed reviews about swapping out the I-6 for a smallblock. To many complaints. If I can keep mu old reliable without having to do any modifications to fit a new engine in, I rather keep it simple. Now, the parts that I have listed total about $1,200. And if you're getting your engine replace, why not put a new radiator in, new clutch and throw out bearing, and add some asthetic parts as well. The guy who's pulling my engine is throwing all these parts on for free, and all parts are original, except for the clutch. I have about 60,000+ miles on it. It's gonna go sometime in the next 20, 000 miles, and I can pay $136 for the part, get it installed for free saving myself $800 very shortly down the road. The mechanic who is doing the work, said, "if your rebuilding the engine, you might as do as much as possible now, that way 3 months down the road your not back in the shop. Never dawned on me to really give the whole thing an overhaul, but that's what I think I'm gonna try and do. I'll be dropping it off in the shop prob. September 1st, or sometiume aroud there. I will post pic's!!!!
08-04-2007 05:01 PM
spearhunter_1 That looks like a pretty hefty chunk 'o change. I gotta wonder if you wouldn't be farther ahead to do a small block swap...I personally know where I could get two 350's for less than 750.00 each. Not new but run good - no smoke, no tapping or knocking, smooth idle...just my opinion.
08-04-2007 04:28 PM
jeeper95yj Yeah, tell me about it. There's also smaller things that you can do that will either enhance performance and also possibly boost power. I am going to invest a small chunk of change into my jeep when i get this engine rebuilt. Here's my laundry list:

AMS Automotive Cluch Kit for 94-99 Jeep Wrangler YJ & TJ with 4.0L I-6 Engine
In order to ensure optimum performance and lasting durability, AMS Clutch Kits only use quality clutch components that are precision-matched to original equipment standards and above. That’s why every AMS clutch kit contains an all-new pressure plate assembly, clutch disc assembly, release bearing, pilot bearing/bushing and an alignment tool designed for the specific application.
» Click here for details $120.99 #52002.18 » Add to cart

Replacement Radiator for 92-02 Jeep Wrangler YJ & TJ
This 2 core aluminum High capacity radiator for 92-02 Jeep Wranglers cools more efficiently than a standard 3 core model. Works with 4 or 6 cylinder engine and manual or auto shift transmissions. Includes draincock.
» Click here for details $179.99 51210.09 » Add to cart

FlowKooler Water Pump for 91-02 Jeep Wrangler YJ, TJ with 2.5L 4 cyl & 91-99 Jeep Wrangler YJ, TJ with 4.0L 6 cyl
FlowKooler water pumps solve low-speed overheating problems by doubling the water flow rate at low RPM & idle. At 3,500 RPM the flow rate returns to normal to prevent excess water flow at high speed. Independent testing proves that FlowKooler water pumps produce 20% more gallons per minute at 2000 RPM & 100% more gallons per minute at 900 RPM than any other pump on the market today, including expensive racing pumps.
» Click here for details $104.99 #51212.58 » Add to cart

Fan Drive Clutch for 84-00 Jeep Wrangler YJ & Cherokee XJ
» Click here for details $54.99 #51202.03 » Add to cart

Aluminum Valve Cover in Red for 93-04 Jeep Wrangler YJ & TJ, Cherokee XJ & ZJ with 4.0L
» Click here for details $99.99 51104.08 » Add to cart

Performance Distributors Black Distributor Firepower Cap and Rotor in Red for 91-99 Jeep Wrangler YJ & TJ
The 4.0L Cap and Rotor Kits feature brass terminals which provide superior conductivity and corrosion resistance over original aluminum terminals. The Firepower Caps and Rotors have excellent dielectric strength and resists carbon tracking. Choose Black, Blue or Red. For 94 and 95 model years please be sure rotor button is 1/2 opening with no peg.
» Click here for details $24.99 #55101.601 » Add to cart

OEM Distributor for 91-97 Jeep Wrangler YJ with 4CYL Fuel Injection
» Click here for details $136.99 #55102.07 » Add to cart

Livewires Billet Aluminum Spark Plug Wire Separators for all 6 & 8 CYL
» Click here for details $49.99 #55112.990 » Add to cart

DUI Spark Plug Livewires in Red for 91-99 Jeep Wrangler YJ & TJ with 4.0L 6 CYL
» Click here for details $84.99 #55112.131 » Add to cart

Optima 12 Volt Red Top Starter Battery
Ultra-Heavy Duty batteries with Spiralcell technology provide 800 Cold Cranking Amps at 0 degrees F for easy starting on the coldest mornings. Spiralcell construction is more resistant to shock and vibration than normal batteries, and is perfectly suited for off-road vehicles. These completely sealed batteries never need water or maintenance of any kind. If one needs charging, it can be fully recharged in about three hours.
» Click here for details $164.99 #17003.01 » Add to cart

Kentrol Polished Stainless Steel Battery Tray for 91-95 Jeep Wrangler YJ
Kentrol Inc.® introduced the idea of Stainless Steel Accessories for Jeep® vehicles in 1980. By manufacturing high-quality products from stainless steel, they have set the industry standard. All products are produced from T-304 stainless steel, which is a non-magnetic and rust-free material that can be highly polished to a mirror finish. Kentrol inspects 100% of their parts before they ship. Attention to detail helps ensure the products you receive will be of the highest quality.
» Click here for details $59.99 #55000.103 » Add to cart

AIRAID® Throttle Body Spacer for 91-06 Jeep Wrangler YJ, TJ, Unlimited, Cherokee XJ, Commanche MJ & Grand Cherokee ZJ, WJ with 4.0L 6 Cylinder Engine
Bolt On Horsepower!
The PowerAid Throttle Body Spacers from AIRAID Premium Filter Company are designed to greatly improve the low-end torque and horsepower characteristics of your engine. PowerAid accomplishes this by spacing the throttle body one inch and adding a dyno-proven Helix style bore(s). As the intake air passes through the spacer, the Helix bore creates a vortex action that improves atomization creating a more complete combustion and an efficiently burning engine. The results are improved drivability and increased fuel efficiency. The PowerAid spacer is 50 state legal, will not void your new car warranty, and can be used with any grade fuel.
Proudly Made in the USA.
» Click here for details $74.99 #17008.001 » Add to cart

Rubicon Express 62MM Throttle Body for 91-04 Jeep Wrangler YJ & TJ with 4.0L
Our throttle body is an all new construction from 6061 T6 aluminum. Features include improved bearing and blade design, largest possible bore size, red anodized finish and easy installation. Installation can be done in less than thirty minutes. Due to increased airflow up to 15 additional horsepower can be produced in basically stock engines. A high flow air filter is recommended for maximum benefit.
» Click here for details $370.99 #RE1062 » Add to cart

Daystar 1 inch Riser Motor Mounts in Red for 87-04 Jeep Wrangler with 6 Cylinder
» Click here for details $79.99 #16057.004 » Add to cart

Skyjacker Transfer Case Lowering Kit for 87-95 Jeep Wrangler YJ with 2"-4" Lift
Any suspension lift kit of 2" or more can benefit from a Transfer Case Lowering Kit to minimize or eliminate any driveline vibration by decreasing driveshaft angles and making them closer to stock. Skyjacker's Transfer Case Lowering Kits feature newly designed 1-piece spacer bars, which look great & simplify the installation.
» Click here for details $36.99 #16006.102 » Add to cart

All of this is courtesy of
08-03-2007 03:51 PM
daddyjeep Very good reading. Thanks for doing the leg work for this stuff. Now I want to build one.
08-02-2007 08:56 AM
jeeper95yj PT II

Stroker combinations

I've outlined eleven stroker combinations below based on budget and desired horsepower levels. To get maximum benefit from the stroker engine you need a free-flow intake with Powerstack or K&N cone filter, 62mm bored HO throttle body, header, high-flow cat, performance muffler and 2.5" exhaust piping.

4.6L Low-buck, low CR "rockcrawler"

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Silvolite UEM-2229 +0.030" bore pistons
Increase piston dish volume to 30cc
8.75:1 CR
Crane #750501 192/204 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mill block deck 0.035"
Mopar/Victor 0.043" head gasket
0.058" quench height
Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines
234hp @ 4500rpm, 311lbft @ 3300rpm

4.5L "Poor man's" simple stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Sealed Power 677CP standard bore pistons
9.2:1 CR
Stock 4.0 camshaft
Ported HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.088" quench height
Ford 24lb/hr injectors with stock 39psi FPR for '87-'95 engines, stock injectors with stock 49psi FPR for '96 and later engines
247hp @ 4900rpm, 300lbft @ 3500rpm

4.5L Low-buck simple stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Jeep 4.0L 3.875" standard bore pistons
9.7:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Stock 0.051" head gasket
0.081" quench height
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
266hp @ 4950rpm, 322lbft @ 3500rpm

4.6L Low-buck stroker

Option 1: Same as above except:
Speed Pro H825CP +0.030" bore pistons
9.6:1 CR
Mopar/Victor 0.043" head gasket
0.081" quench height*
265hp @ 4900rpm, 325lbft @ 3500rpm

Option 2: Same as "rockcrawler" except:
Piston dish volume 22cc
9.5:1 CR
Crane #753905 204/216 degree camshaft
Ford 24lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
262hp @ 4800rpm, 325lbft @ 3500rpm
4.7L medium-buck stroker

Jeep 4.2L 3.895" stroke crank
Jeep 4.0L 6.125" rods
Custom +0.060" bore pistons with 1.38" pin height & 25cc dish
9.5:1 CR
Crane #753905 204/216 degree camshaft
Ported big valve 2.02"/1.60" cylinder head
Mopar/Victor 0.043" head gasket
0.043" quench height
Flometrics F&B 68mm billet TB
Accel 26lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Accel 26lb/hr injectors with stock 49psi FPR for '96 and later engines.
269hp @ 4800rpm, 334lbft @ 3400rpm

4.8L medium-buck stroker

Option 1: Same as above except:
Custom 4.0" bore pistons with 1.38" pin height & 23cc dish
10.0:1 CR
CompCams #68-235-4 210/218 degree camshaft
284hp @ 4900rpm, 345lbft @ 3600rpm

Option 2: Same as Option 1 except:
Jeep 4.2L 5.875" rods bushed for 0.912" floating pin
Small Block Ford UEM-KB364 hypereutectic pistons
Mill block deck 0.017"
0.051" quench height
4.9L high-buck stroker

3.98" offset-ground stroker crank
Jeep 4.2L 5.875" rods
Small Block Chevy UEM-KB142 hypereutectic pistons
10.5:1 CR
Crane #753941 216/228 degree camshaft
Ported big valve 2.02"/1.60" cylinder head
Mill block deck 0.017"
Mopar/Victor 0.043" head gasket
0.053" quench height
Flometrics F&B 68mm billet TB
3.0" exhaust system
Ford 30lb/hr injectors with adjustable FPR or MAP adjuster for '87-'95 engines, Ford 30lb/hr injectors with stock 49psi FPR for '96 and later engines.
Custom PCM programming
300hp @ 5000rpm, 354lbft @ 3700rpm

5.0L Very high-buck stroker

4.06" offset-ground stroker crank
Jeep 4.2L 5.875" rods
Small Block Chevy UEM-KB142 hypereutectic pistons
11.1:1 CR
Crane #751111 238/248 degree solid lifter cam
Ported big valve 2.02"/1.60" cylinder head
OEM 0.051" head gasket
0.038" quench height
Flometrics F&B 68mm billet TB
3.0" exhaust system
Ford 30lb/hr injectors with adjustable FPR or MAP adjuster
Custom PCM programming
328hp @ 5250rpm, 375lbft @ 3800rpm

here's the link in case you want to see the pictures
08-02-2007 08:56 AM
rebuilding your engine?? Get Stroked!!!

after I posed the question of is it possible, or plausible to get your engine bored out for more horsepower somone suggested getting my engine stroked. Here's what I got when looking it up and boy does it look like something that I want to do!!!

4.0 engine torque curves

The torque curve of the engine in stock form was already broad and flat. The addition of some simple bolt-on performance modifications increased torque throughout the rev range, particularly at higher revs.
Maximum horsepower increased from 193hp @ 4850rpm to 235hp @ 5250rpm, and maximum torque from 239lbft @ 3500rpm to 269lbft @ 4000rpm. The torque curve is broader, with at least 242lbft (1.0lbft/ci) available from 1600rpm to 5100rpm.
This translates into faster acceleration at any speed in any gear making passing manoeuvres safer. Gas mileage remained the same despite the higher HP/TQ outputs thus reflecting the engine's greater efficiency.

When 4.0 litres and 280lbft aren't enough...

There's no replacement for displacement so if you want even more torque, you need a bigger engine.
The 4.0L engine has a 3.411" stroke, 3.875" bore, 6 cylinders, and a displacement of 241.5ci (3956cc).
You can increase the displacement of your 4.0L engine by installing a stroker kit.
At the heart of the kit is the 3.895" stroke crankshaft that was used in the AMC/Jeep 258ci (4.2L) I6 engine.
On an engine with the stock 3.875" bore, the stroker crank increases displacement to 276ci (4517cc or 4.5L).
Add 30 thou or 60 thou overbore pistons and displacement is increased to 280ci (4587cc or 4.6L) and 284ci (4657cc or 4.7L) respectively.
If you're feeling really brave, you can overbore your engine to 4.00" and use custom forged pistons. The block must be sonic-tested to ensure that there's adequate cylinder wall thickness before overboring this far. Displacement with the 3.895" stroker crank is increased to 294ci (4812cc or 4.8L). The next step up the ladder includes an offset-ground 3.98" stroker crank that increases displacement to 300.1ci (4917cc or 4.9L). The ultimate stroker includes an offset-ground 4.06" stroker crank producing a displacement of 306.1ci (5016cc or 5.0L).
Here's some information on how you can build a stroker engine and the kits available.

Budget stroker build-ups

Robert Bryce built the world's first budget Jeep I-6 stroker engine, reusing as many stock components as possible in his assembly to keep cost to a minimum. The key to success was to keep it simple. Click on the image to the right to find out more.
Not to be outdone, I also jumped onto the stroker bandwagon and built the world's first "square" Jeep I-6 stroker engine with a bore and stroke of 3.895". It's a slight variant of the 4.6L low-buck stroker option 1 shown below. I transformed a junkyard 4.0L short block plus a pile of parts into a rip-snorting torque monster with a displacement of 4563cc (4.6L), hence I entitled my stroker story "From Junker to Stroker".
My stroker engine's producing a calculated 258hp @ 4850rpm and 320lbft @ 3500rpm. At least 278lbft (1.0lbft/ci) is available from 1500 to 4850rpm. The difference in performance over the old modified 4.0 is very noticeable, particularly from 1500-4000rpm where I need it most. Performance-wise, the stroker engine has hit the bullseye!

Accurate Power stroker kit

Limeyjeeper built the 4.0L engine from his '99 WJ into a 4.6L stroker engine using this kit. It produced 210.5hp @ 4800rpm and 262.4lbft @ 3800rpm on the chassis dyno. Assuming a 20% drivetrain loss (RWD auto.), that's 263hp and 328lbft at the flywheel.
Here's the link to Limeyjeeper's stroker story.

Specs are the same as the medium-buck stroker shown below except for 0.030" overbore, Ford Motorsport 24lb/hr injectors, stock intake, and 62mm TB.
Accurate Power ceased trading in April 2005.
Hesco stroker kit

Available for all Jeeps in .030 or .060 oversize. Click on the image to the right.
A Hesco 4.7 stroker dyno'ed 267hp @ 4700rpm and 332lbft @ 3400rpm at the flywheel. The specs of that engine are in this Yahoo Stroker Group message.

Another Hesco built 4.6 stroker did even better on the engine dyno, producing 269hp @ 4800rpm and 339lbft @ 3200rpm.
Other stroker kits

Other stroker kits worth mentioning are supplied by Speedomotive and by RPM Machine
You can also get a complete 4.6L stroker longblock engine from Golen Engine Service or Custom Design Performance

The Golen 4.6L stroker has been reviewed by JP magazine, producing 268hp @ 4900rpm and 324lbft @ 3900rpm on the engine dyno.

Accurate Power and Jakes Racing Engines have ceased trading, while Clifford Performance continue to trade but no longer supply stroker kits.
Injector sizing

Stroker engines require oversize injectors to provide adequate fuel and prevent pinging due to lean air/fuel mixtures. Click on the image to the right.
To calculate optimum injector size, use the following formula:

Injector flow rate (lb/hr) = [Expected HP x 0.5 (BSFC)] / [no. of cylinders x 0.8 (injector duty cycle)]

The actual injector flow rate from each injector depends on the fuel pressure (FP) in the injector rail. Most injectors have rated flows at 43.5psi fuel pressure. The actual flow rate from each injector is:

Actual injector flow rate = Rated injector flow rate at 43.5psi x square root of (FP/43.5)

Adjustable fuel pressure regulator

Fine tune your engine's fuel curve with a Hesco adjustable fuel pressure regulator (FPR). Click on the image to the left.
The fuel pressure can be adjusted to provide the optimum air/fuel ratio.
Part no. for the '87-'90 FPR is HES8790FR
Part no. for the '91-'95 FPR is HES9195FR

There is no adjustable FPR available for '96 and later engines.

Stroker engines need a longer duration than stock camshaft to maximise horsepower and torque. Click on the image to the right to go to the CompCams catalog.
The aim is to produce maximum torque over as wide an rpm range as possible. Stroker engines built with a compression ratio (CR) of about 9.5:1 will derive maximum benefit from these camshafts:

Crane #753905 204/216 degree cam
CompCams #68-231-4 206/214 degree cam

A stroker built to a CR of 8.8:1 that'll run with 87 octane fuel will benefit from a shorter duration dual-pattern cam for more low rev torque:
Crane #750501 192/204 degree cam
CompCams #68-115-4 192/200 degree cam
Long rods vs. short rods

If the Jeep 4.2L 5.875" rods and stock Jeep 4.0L pistons are used, the pistons will be 0.008" further down the bore at TDC than those in the stock Jeep 4.0L engine. The deck clearance is thus increased to 0.030" and the quench height is increased to 0.081". The resultant CR is 9.7:1 with stock bore pistons and 9.9:1 with 0.060" overbore pistons. If the block is decked 0.010" to return the quench height to stock, the combustion volume is reduced by 2.0ml and the CR is increased to 9.9:1 and 10.1:1 respectively. Premium fuel will be required to prevent detonation.
If the stock Jeep 4.0L 6.125" rods are used, expensive custom forged pistons with a shorter pin height than stock (1.380") are required to achieve zero deck clearance. Using longer rods does enable you to choose pistons with a larger dish volume than stock. These reduce the CR and allow the use of low octane fuel without detonation. You can also use a shorter duration camshaft for increased low-rev torque, and select the head gasket thickness required to achieve the desired 0.040"-0.060" quench height.
If you use the shorter Jeep 4.2L rods with cheaper cast aluminium or hypereutectic pistons, the quench height can be reduced by milling the block deck and installing a thinner head gasket. The CR can be reduced by increasing the combustion chamber volume and the piston dish volume.
*For each 0.010" milled from the block deck (or taken from head gasket thickness) to reduce quench height, the combustion volume decreases by ~2.0ml and the CR increases by ~0.2*.

Stroker engine math

Here are some formulae, and how they apply to the stock Jeep 4.0L engine:

1. Deck height = Rod length + stroke/2 + piston pin height + deck clearance

9.453" = 6.125" + 1.705" + 1.601" + 0.022"

2. Combustion volume = Combustion chamber volume + head gasket volume + deck clearance volume + piston dish volume

84.6cc = 56.7cc + 10.5cc + 4.3cc + 13.1cc

3. Compression ratio (CR) = Cylinder volume/combustion volume + 1.0

CR = 660/84.6 + 1.0 = 7.80 + 1.0 = 8.80

4. Quench height = Deck clearance + compressed head gasket thickness

0.073" = 0.022" + 0.051"

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