Jeep Strokers

Little info on what I have since I'm new here. I found this site researching to build a stroker and this site was mentioned a few times on Pirate4x4 and JeepForum. So here I am asking for help. I've researched and researched for the past few days on my free time and I'm sure my questions have a answered in a build thread somewhere.

While I wheel my 01 TJ, I am building a second Jeep. I have a 89 YJ that has a 79 Ford Dana 60 and a Dana 70 sitting underneath of it. I plan on running a 5spd NV3550 and a flipped Dana300............yada yada yada.

I thought about a V8 swap and I was going with a 5.0 because my goal on this Jeep is to build it correctly, not cutting corners but on a low budget. So I am doing all the work myself, scouring the classifieds to see what I can find and using help from a buddy this is how I'm building this Jeep. I wanted to build on a budget so I have a trail rig up and going soon so I can tear down my TJ to restore and throw big dollar items at it, like an Atlas, coilovers, etc.

I am going to be running a 3link and 4link with coil springs on the YJ to save on cost. I had a line on a 5.0 that was a decent price but I never pulled the trigger to get it. I then came across a 2004 4.0l with 110,000 miles on it and the guy said it had a knock to it but never loss oil pressure. His mechanic said the head was in great shape. Pulled the oil pan found a few metal shavings, but the rod bearings where fine and the pistons from the bottom looked fine. So it could be a wrist pin or a bearing gone bad. Great for a rebuild because the cylinder walls still looked good.

When I first got the Jeep I sold the 4.2 drivetrain out of it before I decided on a motor. I did this to recoup some money back from buying this project because I knew I wanted more then the 4.2 could offer.

Now researching strokers I wish I would have kept the engine. Luckily the HP dana 30 I have from the YJ another guy with a 4.2 wants to do an even trade, so I'm getting a 4.2 back for the crank and rods.

I don't want to pour a lot of money into the motor for various reasons but I want a strong, long lasting motor so I will compromise if I have to. Here is what I have looked up and what I have on the calculator

4.5L
YJ 4.2 Crank
YJ 4.2 Rods
2004 4.0 Stock Head/Cams (Up in the air, may go with a aftermarket mild cam, help!!!)
Recommend a piston if I can't use the 4.0 OEM pistons

Bore = 3.875 (Might bore .030 over depending on closer look at the walls)
Stroke = 3.895
Combustion Chamber = 58cc
Deck Clearance = 0.00
HG Thickness = .051
Gasket Bore = 4 inches
Dish = 23cc
Connecting Rod Length = 6.123
Cam Intake Duration = 253 degree (OEM cam)
Cam Lobe Separation Angle = 114.3
Advance/Retard = 0 Degrees

Cubic Inches = 275.61
Liters = 4.52
Static Compression = 9.23:1
Dynamic Compression = 7.63:1
Quench = .051 (I'd like to keep this as close to this number as possible. From reading the lower this number can be the better the motor will run and last)
Intake Valve Closing Angle = 60.8

I plan on running all OBD2 stuff for various reasons. The gas tank will be an aftermarket in the rear with a TJ fuel sending unit. I believe I need to use ford 24lb injectors (unless you have other suggestions)


This will be my first Jeep engine build. I have a friend who has built several 4.0's to OEM spec to help.

Will the longer rods hold up for a long time or should I go with the 4.0 shorter rods and custom pistons ($$$). I'd rather stay on the cheaper side if the longer rods will be fine. This will be a driver/trail rig. Drive to the trails 65-70mph and run rocks/muddy trails.

Any help would be great.

Sorry for the long read.

-jb- wrote: 2004 4.0 Stock Head/Cams (Up in the air, may go with a aftermarket mild cam, help!!!)

If you use the stock cam and lifters keep the lifters in order so they go back on the specific lobe. Inspect the cam very carefully. I have a 2000 and a 2003 stock cam that shhow damage with low miles.

Recommend a piston if I can't use the 4.0 OEM pistons

The machine shop may not be able to get the piston off the rod with out damaging the piston.

Will the longer rods hold up for a long time or should I go with the 4.0 shorter rods and custom pistons ($$$). I'd rather stay on the cheaper side if the longer rods will be fine.

You have the rod info 100% backwards. The 4.0L rod is 6.123" long. The 4.2L rod is 5.875" long. The longer 4.0L rod is considered better for piston longevity and advertised to give more torque. You will need either the KB944/IC944 pistons, the Bulltear pistons, or custom pistons to use the 4.0L rod. The 4.0l pistons can be used with the 4.2L rods.

On the deck clearance/quench. Instead of going with the .051" gasket and 0 deck, do with the .044" gasket and .007" deck clearance. Less cutting.

Thanks for the help.


How well will the 4.2 short rod hold up? This is not a race vehicle, I let her crawl and only give into the gas when she needs it over an obstacle.

If I can get the 4.0 pistons off the rod without damage, are they fine to use stock? Or do they need to be CC'd?

I'll check the cam out to see what it looks like, if I need a replacement any suggestions on a mild cam? Can I reuse the lifters/rockers or do I need all new?

Thanks for the deck clearance/HG suggestion, I'll go this route.


Any links where I can order a HG and look at piston prices.

Suggestions on pistons to use on the 4.2 rods if I need new ones?

So changing my numbers a little I think I came up with something a tad better

Bore = 3.875 (Might bore .030 over depending on closer look at the walls)
Stroke = 3.895
Combustion Chamber = 58cc
Deck Clearance = 0.0215
HG Thickness = .043
Gasket Bore = 4 inches
Dish = 23cc
Connecting Rod Length = 5.875
Cam Intake Duration = 253 degree (OEM cam)
Cam Lobe Separation Angle = 114.3
Advance/Retard = 0 Degrees

Cubic Inches = 275.61
Liters = 4.52
Static Compression = 9.01:1
Dynamic Compression = 7.47:1
Quench = .0645
Intake Valve Closing Angle = 60.95


In red is what changed on the calculator. My first recipe had the wrong rods configured using the 4.0 rods. I want to use the 4.2's so I don't have to order expensive pistons. Would also like this to run on pump gas with no pinging.

Not going to deck the block or head if it doesn't need it. Also going to use the STD bore if I can. I don't want a high hp motor. Something a little better then a 4.0, easy on the wallet, last long and has decent power on the trails.


Look better, improvements?

That 23cc dish isn't a stock nor off the shelf dish size. . .

gradon wrote:That 23cc dish isn't a stock nor off the shelf dish size. . .

Yeah I know, from reading there are certain pistons that have enough material that you can have them dished by ocelot (?spelling)

Apparently the silvolite 2229s can be dished out to the high 20ccs, but they aren't hyperteutic. Oleshot is the dish man.

-jb- wrote:Yeah I know, from reading there are certain pistons that have enough material that you can have them dished by ocelot (?spelling).

It's Oleshot actually.
Anyway, your 4.0 block is 110k miles old and you won't be reusing the original pistons to build the stroker, so I suggest you overbore the cylinders and base your build on one of the 4.6L recipes on my site (click on link in my sig.).