Should I build a Jeep 4.6L inline six stroker motor or swap a V-8?

[60Bubba]

Moses, I have watched your videos regarding how to approach a stroker motor.  I have read tons of info on the internet, and I've seen many calculators for quench height, combustion cylinder volume, etc.  It really is baffling to me, and I've begun to realize I could invest a lot of money and end up with an engine that doesn't work.

Is there any identifying info on the block that would allow you (or someone) to write me a "recipe" for what parts I need to build up a stroker? I'm realizing that the added weight of the full size truck axles and 38" tires are going to necessitate more power.  I've been thinking about Ford 302 power, as I have secured a 1993 EEC IV harness and computer, but that swap has its own challenges.

I always thought a stroker was the best way to spice up my powertrain, and I still like the idea if I can be relatively certain if what parts I need to buy to get it right the first time.  Please let me know what you think.

[Moses Ludel]

60Bubba...A stroker, in my view, is always a way to go.  That includes V-8s as well as inline Jeep sixes.  My bias is about the quicker torque rise of a stroker engine (with the right camshaft choice!) and its ability to run well at extremely low speeds under load.  This has been strongly proven by my experience with 350/383 Chevrolet V-8s and the Jeep inline six 4.6L builds.

First, it's best to say that we're looking for trail, stump-pulling power and not an Ultra4 buggy engine, although even an Ultra4 can do well with a closer to square bore/stroke configuration.  The idea is torque rise and higher manifold vacuum at low speeds, and here the 383 Chevrolet build, a Ford 351W build, a GMC 302 four-main bearing inline six from the Stone Age, a Ford 300 cubic inch inline six or, yes, a Jeep 4.0L/4.6L stroker has the edge.

On that level, I would use a 351W before horsing around with a 302.  Bigger crankshaft bearings, better bore/stroke ratio, more torque.  For off-road use, you would be better off with a stock 300/4.9L cubic inch Ford MPI inline six (blasphemy for Jeep buffs!) than a 302 V-8 for low-end torque.  Built right, a 351W or 300 Ford inline six would have more torque than a 4.6L Jeep engine.  Worth mentioning, low range use would level the playing field in any case, but you would need to rev a 302 V-8 higher to produce good horsepower and torque numbers.  It would be more prone to stalling under severe load, although MPI and MAF do compensate for a stable throttle/idle speed.  The good news for the Ford 302 V-8 is its light weight and compact size for an engine swap.  The 351W is not bulky, either.

This brings up the issue of whether you need a stroker for low range use.  I would say, "Yes!" in your situation.  You do drive on the highway, and your Jeep CJ-7 must be pushing 4,000 pounds by now.  (It would pay to run the Jeep over scales at its normal "wet weight" to see...Please share the results.)  Fuel efficiency must be lagging on-highway if that's an issue, and arguably a stroker 4.6L with the right camshaft should improve fuel efficiency. 

Where you would benefit most off-road with a stroker six or the right V-8 would be finesse driving at extremely low speeds—without killing the engine.  I built an FJ40 Land Cruiser project for OFF-ROAD Magazine in the late 'eighties.  The vehicle was destined for the Rubicon Trail and even trailer pulling/testing with a 90-inch wheelbase.  My engine build choice was a 350 Chevy V-8 with a 400 crankshaft:  the popular 383 bore stroke of 4" bore (+ 0.030") and 3.75" stroke.  (Stock 350 stroke is 3.48".)  I ran the same CompCams 252 grind camshaft that Tony Hewes and I still recommend for rock-crawling engines like your 4.0L or a 4.6L build.  I also, and purposely, added Chevrolet's big 168-tooth flywheel for more flywheel mass. 

This flywheel trick is often overlooked, a secret for keeping an idle speed, rock-crawling engine ticking over.  The 383 had high manifold vacuum at low speeds and delivered strong highway performance and good fuel efficiency.  It pulled a 21' Starcraft trailer in a windstorm...and it also scaled the Rubicon Trail at a snail's pace on big rocks, with the clutch engaged in low-low and my foot applying the brake.  This carbureted engine would not die when forced to run as low as 350 rpm—and this was at 7,000 feet elevation with a 3-5% loss of horsepower per 1000 feet of elevation!

All of this stated, for your Jeep a 4.6L build would be a bare minimum.  Considering the modest additional cost, I would not rebuild a 4.0L as a stock engine...My personal build (camshaft pick, compression ratio, injector sizing, etc.)  is described thoroughly at the magazine.  The actual build is not rocket science and should not be dwelt upon.  There are a few serious considerations:  1) decking the block to match piston height at TDC, 2) selecting the right pushrod lengths for the decked block and cylinder head, and 3) picking a sensible compression ratio.  The rest of the build is, frankly, the same as building any later Jeep 4.0L or a 232/258 inline six.  You will not have challenges beyond matching the piston heights to the block deck, and this is a relatively minor, regularly performed machine shop task.  This simpler view demystifies the "quench" and other esoteric discussions.  Make sure the lifter preloads are correct by fitting the pushrod lengths.  CompCams is your neighbor, and its adjustable pushrod gauge provides a quick test for proper pushrod lengths.

As for which 4.0L block or head to use, I'm biased by the late '90s head and block, as there are issues with earlier and later castings.  None of the castings should be a problem if you keep the bore to 0.030" oversize and, if concerned, have the block sonic tested before and after boring to see whether there is core shift at the cylinders.  The engines to avoid as a rule would be '87-'90 Renix 4.0L types with the wrong cylinder head, although in fairness to low-budget owners who have used the earlier Renix for a stroker build or engine swap, I'm sure that engine works okay on the trail.  I would, however, opt for a '91-up Mopar MPI engine with the later cylinder head design.  I would avoid the 2000-up head castings if you have a choice, though many engines have survived with that cylinder head in place, and I wouldn't make a major issue out of this if it's part of your existing engine.  (Though not ideal, the 2000-up/COP engine's valve sizing is just fine for off-road crawling and highway use.)  Provide your block and cylinder head casting numbers, we'll discuss their application and merits.

Overall, if you want V-8 power, then swap in a V-8.  On that note, if you really like Ford, do a 351-Windsor MPI engine and wade your way through the ECM/computer and wiring.  If you like G.M., a nice build would be a TBI or even a Tuned Port 350 with a 400/stroker crankshaft.  If you like Chrysler, do a 5.7L Hemi if you can solve the PCM/wiring riddle easily.  G.M. has street rod engines with California E.O. numbers (the only manufacturer to offer a street legal multi-port fuel injected crate engine), but you would want a 5.3L or 5.7L LS with a very mild roller camshaft grind.  Your Jeep is not a street rod.

We can kick this around.  A 4.6L build would be night-and-day better than your current performance and a possible cure for your Jeep's growing weight problem.  (Bi-pass surgery is out of the question!)  The torque is impressive for the displacement.  Worth mentioning, however, is the old adage:  There is no substitute for cubic inches!

Moses

 

[60Bubba]

Moses,

Seems like sage advice as always! It sounds like I'm well setup if I decide to go the stroker route.  My current engine is out of a 1995 Cherokee. It has the 7120 head that is the best of breed from what I've read.  I haven't ever been inside of it, so I don't know what the condition is.  It still makes good oil pressure, so I suspect it will be a decent canvas to work from. 

That said, last night I plunged into an engine purchase on Rockcrawling Classifieds.  A gentleman in Colorado that races prerunners in the 2.3L class had considered stepping up to the V8 class.  He rebuilt a 1994 Bronco 302 (he's an engine mechanic) and then realized he couldn't afford to be competitive with the V8 crowd.  It's a complete motor (minus exhaust manifolds and oil pan) with ECM and harness.  I paid $250 for all and will pick it up when I go out to Moab in May.  It may be a total scam, as it sounds too good to be true. I can afford to lose $250 if so, but on the off chance that it's legit, I decided not to pass it up.  For that money, I can sell the harness, ECM and some other parts even if there's a hole in the side of the block and not lose much!

I think the truck 302s didn't make as much HP, but I do believe they made more torque down low.  Does that sound correct?

With such a small investment in my V8, I'm willing to change my mind based on the easiest/most cost effective swap.

[Moses Ludel]

60Bubba...Well, I did say a few good things about the 302, right?  I happen to be a 351W fan with its larger crank bearing journals, but the 302 will work well, and especially at the price!  Ford used the World Class T-5 behind this engine in H.O. Mustangs, the transmission is now rare, Advance Adapters once sold brand new WC T-5s by the pallet-full before the well went dry.  A World Class T-5 would be nice, but if not, a truck 4-speed like the T18, T-19 or my favorite, the NP435 that Ford also used in trucks, a great unit except for the lack of overdrive.  For a heavy duty 5-speed with Ford, you'd need a ZF or some way to do an NV4500 (GM and Dodge used them, not Ford, though). 

In your case, you already have the perfect transmission:  the Warner T-19 that you built, you can use all Ford parts with the adapter you now have for the Dana 300!  This actually tips the scale in the direction of a 302/351W over a 4.6L stroker six!  You're halfway home with a Ford V-8 swap.  A Ford bellhousing, flywheel, pilot bearing, clutch assembly, T.O. bearing, release arm and slave cylinder, a sensible mate-up to your clutch linkage if possible, and go for it!  You may have some of these parts with this 302 engine package and perhaps some crossover parts that came with the T-19 swap? 

For those interested, here's 60Bubba's Warner T-19 conversion into his Jeep CJ-7:  

Tune on the truck 302 is much better for your usage, its still an MPI engine, nothing lacking.  You're not interested in H.O. mid-range and high speed performance, you want the power off-idle and through the mid-range.  The fit of that engine will be very neat and clean.  Should have no issues, you can isolate heat from the steering column with tubular headers.  They'll flow well, too.  Make friends with a muffler shop locally to fit the rest of the exhaust system and its bends, a muffler/mufflers and cat(s) if you need the cat for registration or to quiet down the ECM codes.  O2 sensors should follow the Ford scheme unless you have a better, more functional approach.  A big single exhaust system or dual-exhaust will work, you can emulate the '94 Bronco in that regard.  For an oil pan, you want a rear sump to clear the front axle and a matching 4x4 oil pump with the correct pickup tube. 

Conservative, cheap and a real small-block V-8.  You could always do a 351W in the future if this engine does have issues.  A wise move overall, once past the adapters and weld-in motor/frame brackets.  Advance Adapters can help with the adapters and mounts, see the catalogs.  With a V-8, you'll never find yourself questioning a 4.6L six-cylinder stroker build.  You'll like the compactness of the 302 V-8 and its distributor at the front of the engine (so, too, with the 351W)...Take and post lots of pictures when you tackle this swap. Everyone will be interested!

May is a good time for Moab, long after EJS...EJS has worn thin, I'm trying to get out of it this year.  Unless a substantial video assignment pops up, I'll bow out.  I pull the travel trailer, it's a two-day trip at 716 miles each way.  Used to do the marathon one-day drive each way, can't make that kind of time with the 30' travel trailer in tow, and I wouldn't anyway...I've done a dozen of the EJS events, each a heavy work week for me with jacked up prices and hoards of people (some think that's fun) plus a half-dozen consulting jobs, mostly trail guiding media journalists on behalf of Tread Lightly during new 4x4/SUV vehicle launches in the mid-'nineties.  Ugh...Rather do late April or May, away from Spring Break, too.  October/early November would be nice...The area is drop dead gorgeous with wonderful OHV trails.  I know, I've driven or hiked up most of them, mostly with cameras or video gear in tow!

Moses