Jeep Strokers

So I go rid of my taco and got me a wrangler. It's my first jeep. Yay. It's also the second gas 6cyl Ive ever owned. Yay mpgs. It's got a 2.5 and I've already decided to 4.0 stroked. I love strokin. My question is where to start? What lock should I be lookin for?

Gmm213 wrote:It's also the second gas 6cyl Ive ever owned.

It's got a 2.5 and I've already decided to 4.0 stroked.

Is it a 2.5 or a 4.0l?

What lock should I be lookin for?

Lock?

Crap sorry bout that. It's a 2.5. I should have said it only the second non v8 gas I've owned and I meant block. My damn phone is to slow

What year is your Jeep?

95

You have a temp sensor in the back of the head that feeds the dash temp gauge, so you'll at least want the '91-95 7120 head. You can extend the wire and drill a boss into the t-stat housing to relocate the sensor and use a newer 0630 or 0331 head, but to keep it simple for the newbies, use the same era head. I'd recommend a crankshaft from a '87-90 YJ Wrangler with the 4.2l/258 6-cylinder. You can also use the connecting rods from the 4.2l if you want to use off-the-shelf 4.0l pistons.

Thank you. Also what kind of numbers could I get with this setup? Just generally. I know there's tons of factors

Well before you get ahead of yourself...what do you want from it? What purpose will it serve? What rpm will you be cruising..you understand you will need a matching trans for the 4.0L right? The 4.0L is a strong engine as it when geared correctly already!! Also cost..what are you looking at spending realisticly?

You may look into the 4.2L mini strokers as they can be damn potent and decently cheap! This is the route I took. Basically the 4.2L can be done with a 100% rebuild, a 3.8L crank shaft and appropriate pistons. Other than that you won't need too worry about much! I'd say 1000-1500bucks. I'm about 1800 in now. Thats 3.8L crank, new valve train, pistons, dual roller timing set, machine work ect.
A cheap 4.5-4.6L would put out similar numbers, be LESS efficient, and be less reliable! Thats considering rod ratio, piston speed, quench height ect. Again they would put out similar numbers as well, just food for thought


A decent 4.5L or 4.6-4.7L would cost quite a bit..I'd say 2500 minimum. And again the piston speed would be higher & have a worse rod ratio which in theory would be less reliable! The higher cost would come from more machining to get a better quench height ect..or from doing a long rod stroker ect ect.

I'm using it as a dd an trail rig. I was planning between 3000-3500 for the build. I Heard that 305 pistons are the same bore. Can you use 305 pistons in a 4.0? Is there a better option?

you've got alot of reading to do bud...with 3000, you can built the poor mans 4.6L stroker. It would make around 240hp
Here's a few options & shows basic power output.
http://www.jeep4.0performance.4mg.com/photo3.html

I'm doing the 4.2L milder setup..just altered. 9.4:1 static, 8.18 dynamic. Using a 87-95 cam installed at -2*, 59cc cumbustion chambers, 15cc piston dish, zero deck height. Also using a ported head, that I cleaned up and very lightly ported/gasket matched. I unshrouded the valves & polished the cumbustion chambers to also help fight of detenation. I'll be using 1.55" exhaust valves & 1.93" intake valves. Going to advance the timing 6* and tune it on 91octane...let the computer pull the timing if it wants to.
Basics for me were, good rod ratio, acceptable piston speed, & good quench. The tighter the quench the less chance of detenation & better efficient the motor is! The slight increase in compression is just fine because the tighter quench, so do not worry about that!
The bigger strokers 4.5-4.7L will make the power slightly lower in the rpms than the 4.2L stroker. Just remember with more power & torque comes more strength issues..axles, trans & Ujoints need to hold up to the added power. So I kept mine simple, yet effect & it will run very very very strong & healthy.
I'm estimating 260hp @ 4800rpm, 305ftlbs @ 3200rpm.
The online dyno simulators shows it higher actually, 270/315...but we will see. This is also at the crank!

Deffinetly get a dual roller timing set..fully forged is best. There was a thread not long ago about this! And use just OEM replacement lifters! Sealed power lifters are like 6 bucks each. No need to waste money there
Also you can use the 87-95 cam..its actually a damn good performer. It will hold power from 2400rpm-6200rpm..but if you advance it from -8* to -4*. It will run from around 1800-5600. You can even install it -2* or 0* which would give a even better power band for daily driving..shifter it lower basically. Plus you won't have to worry about the aftermarket cam failures that seem to be happening!


The 4.2L route is so much cheaper because everyone wants the bigger strokers..and so the 258 crank thats needed for that is costing more and getting harder to find! The 199 crank needed for the 4.2L stroker cost around 200 shipped to your door with bearings ready to use. The plus of the 4.2L is with the cran and a 1.58x" pin height piston you get a zero deck, give or take slightly..the bigger 4.5-4.7L strokers need the block to be decked which cost more money. Hence why a good once would cost 3k minimum. With 3000, I would be a badass 4.2L, full balanced out, ported head with SBC valves, get a cam if you want, forged dual roller timing chain, good header, exhaust, 99-01 intake manifold, bored throttle body..every bolt on possible! Thats how I would do it at least!


Also here is dinos other site.
http://jeep4.0performance.4mg.com/
He has the one linked above as well. As well is on these forums. I copied every bolt on he did on my stock 4.0L, its peppy as all hell & gets great mileage. I'm hoping my new stroker will get slightly better mileage with a .040" quench height. Should be much more efficient.

This is exactly why I was looking for to get started. Just to do some planning. So the big stokers use a larger 4.2 crank and the minis use a smaller 3.8? And your saying they make roughly the same numbers just on a different curve?

Gmm213 wrote:This is exactly why I was looking for to get started. Just to do some planning. So the big stokers use a larger 4.2 crank and the minis use a smaller 3.8? And your saying they make roughly the same numbers just on a different curve?

Yes bigger strokers use the 4.2L 258cu crank..has a 3.895" stroker. The mini strokers use a 3.8L 199cu crank with a 3.500" stroke. Stock 4.0 242cu cranks have a 3.410" stroke. The biggest upgrade on the mini strokers is cost is very low, with the crank and appropriate pistons you get a zero deck give or take..so litterally no machine cost to have that done! The bigger strokers will need to be decked for a zero deck. The zero deck gives great efficieny gains..allows for higher compression without the need of higher octane gas because of the tighter quench height!
Honestly I'd love a 4.6L done up right but that would cost me at least 4000 dollars to be realistic! Can be done cheaper but again there is other issues that come with that. Also making sure the trans & transfer & axles can hold that power ect ect..its more than just a motor lol. Also the piston speed & ratio ratio concerned me, more so that I choose to do my 4.2L!


As far as power wise..it truely depends on what you do..cam, ported head ect ect! But essentially if you do it right, yes a basic 4.5-4.6L will make around the same as a 4.2L..just lower in the rpm range..and the bigger motor will cost more & use more fuel...not that thats a concern fro must Of course you could have a all out 4.6L and it would make more than a all out 4.2L...
By all out, I mean high compression, premium grade gas, ported head, cammed, roller rockers ect ect! Bigger motors always will make more when done correctly..but for your budget, I'd do a badass 4.2L...it'll be efficient as all hell..who knows how much mileage it may gain over a stock 4.0..but it'll be more efficient and if taken care of correctly it will last, if not out last a stock 4.0. Its 100% the same except your uipgrading! Piston speed & rod ratio change almost nothing, a forged dual roller timing chain, ect ect..you can make it outlast a stock 4.0!

Porting/cleaning up the head goes a long way! Polish the combustion chambers & exhaust runners will also help alot..polished chambers prevent detenation, and polished exhaust runners keep exhaust moving fast and smooth out of the head! Honestly the head is where you will gain alot I think! The 4.2Ls are very simple to do, crank and pistons & otherwise a stock bottomn end rebuild!
I spent alot of time doing my head with stones & paper rolls. This took more time than using carbide bits but I didn't screw up at all, and I got it exactly how I wanted. Using carbide bits can be dangerous as they take away alot of material very fast..I took the slow and steady route! My chambers & exhaust runners are near glass smooth! My intake manifold..or what I could reach is also glass smooth. the intake runners were cleaned up then polished with 80 grit rolls to help with fuel atomization!
I will be running 1.55" ls6 sodium filled exhaust valves, and 2.00" ls1 intake valves. The intakes will be turned down to a 1.92-1.95"..haven't decided yet. My cumbustion chambers are 61cc currently with stock valves. With the new valves, they have tuliped undersides, I will gain a cc or 2! This may not seem like much but it helps get the quench height as tight as possible, which allows for more compression without detenation! Compression and flow build power in a N/A motor
Focus on the head, try to run tuliped valves & polish up the chambers. Buy a good 7120 cast head and start working on it..then buy your bottom end and build it! Get your head build correctly! Do it badass, 100% like you want..and go slow. Then build up a bottom end and slap them together! Exactly what I did. Alot goes into porting..but its really not bad when you get into it!


My jeep is an 88. It makes 170hp & 220ftlbs in stock form. Its now with 100% bolt ons around 190hp and maybe 235ftlbs. The 4.2L mini stroker with the same bolt ons should be making 250hp minimum and around 300ftlbs..I'm hoping mine will be making slightly more but honestly thats a 80hp jump..you are gaurnteed to notice that lol.

Gmm213 wrote:I'm using it as a dd an trail rig. I was planning between 3000-3500 for the build.

In that case you could build a 4.6L modified "poor man's" stroker and use the change to add all the external performance and supporting bolt-ons (CAI, 62mm TB, header, high-flow cat, catback exhaust, bigger injectors). Mine is an original "poor man's" stroker and it's great fun to drive.