Rebuilding A Jeep Engine In The Driveway - Jp Magazine

Pete Trasborg Brand Manager, Jp

Way back in the July ’09 issue, Trasborg decided to buy a ’68 Jeepster Commando and take it to Moab, Utah, for Easter Jeep Safari. The problem was, the Jeep hadn’t run or drove for about five years and was full of rat scat. We then regaled you of our five-week thrash-fest with things like Marvel Mystery oil, replacing rusted out floorboards, replacing the rear crossmember from a failed Dodge rescue, and more. By the time we got the Jeep to Moab, after wheeling it for a shakedown weekend in the Truckhaven hills, it was in tip-top shape. Or so we thought.

budget Rebuild Part 1 stock Engine Photo 37099782

It ran great through the snow the first two days in Moab and once it got nice, the Jeepster just refused to run well. Junk in the carb and fuel line coupled with ignition problems doomed the Jeep, and even a partial carb rebuild and lots of distributor work couldn’t get it going again for more than a few miles at a time. Trasborg is really good at pulling the carb on this thing apart, cleaning it out, adjusting it, and putting it back together again. Once that got old, we wheeled the tow rig the rest of the week, brought the Jeepster home, and you guys (and maybe at least one gal) haven’t heard of it since.

In the two years since then, we’ve swapped motors, transmissions, and even the T-case. We actually found rodent bones in the bellhousing and other stuff we’d rather not talk about. We rebuilt the engine and transmission mounts, put a rebuilt carb on it, and ran it. Part of the charm of this Jeep is that it doesn’t have an inline-six and the idle of the odd-fire engine in strangely comforting. So, when the loaner engine’s time was coming near, the only logical choice was to rebuild the engine that the Kaiser factory workers originally put between the framerails more than four decades before.

budget Rebuild Part 1 engine Building Tools Photo 37099788

After years of building and breaking Jeeps, our tool boxes aren’t anything to laugh at. However, building (or rebuilding) engines requires different tools than would be used in the normal Jeep buildup. To buy them separately would cost a pretty penny. Fortunately, Summit Racing has teamed up with Craftsman and is now offering application-specific tool kits. We went with the Engine Builder kit for this job and had to actually take the catalog out to prove how little all the tools cost. It is a very complete kit and includes a piston ring squaring tool, piston ring filer, rod bolt stretch gauge, dial bore gauge, ½-inch drive torque wrench, digital calipers, micrometer set, camshaft bearing installation and removal tool, camshaft degree kit, harmonic balancer removal/installation tool, and work gloves.

True to longstanding Jp magazine tradition, when the time came to actually rebuild the engine, we couldn’t stand the thought of someone else doing it—so we decided we’d rebuild our 225ci odd-fire Dauntless V-6 ourselves, in our own driveway. Also true to long-standing tradition, we decided that we might as well get some more power out of it while we were in there and make it more reliable as well. In short, we wanted it all, and we were going to do it all ourselves. We’ve broken the rebuild down into two installments with this one covering the valvetrain, most of the tools needed, and some basic engine rebuilding tips. For the next installment, we’ll finish the bottom end and cover reinstalling the engine where it sat for the 40-plus years before we came around.

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Once you’ve got the engine out, clean it off. We were in full hantavirus-phobia mode with this one, thanks to all the rodent droppings. However, we’ve had great results with using oven cleaner over the years. That is, as long as you don’t care about paint or most anything else. Spray it on, let it bubble and go from white to some yellowish-brownish color, maybe scrub a bit, and rinse off. Well, in this case, we stayed at arm’s length to avoid breathing anything in.

Once we had it cleaned off, we pulled it apart and poked around. By the ridges formed in the walls of the cylinder, it was obvious this engine had seen some use. We were originally just going to hand-lap the valves, but amid concerns for non-hardened valve seats and to get the valves to flow a bit more, we took the heads to our local machine shop to have a three-angle valve job done and hardened valve seats installed to deal with today’s fuel. We’re trying to rebuild on a budget and five-angle valves and seats just weren’t in it. We had some slop in the valveguides, but all of them were under 0.005-inch. The maximum accepted value is 0.0032-inch, but we were keeping costs down so we decided to just run it. It really wasn’t that bad.

We needed to deliver the heads to the machine shop bare to avoid being charged the labor of breaking the heads down. If you’ve never pulled a head apart, you will need some kind of valvespring compressor to get ’er done. The compressor is even more important when putting new springs in. In our formative years, we have been able to get the old springs out using pliers and screwdrivers. Yeah, it’s butch, but it is doable. Then we tried to install the new ones using the reverse method. Yeah, nope, not happening, and that is not to mention the damage that might occur to the new parts, thus costing more money. This Performance Tools compressor is our favorite type. The large jaw uses the valve or combustion chamber itself for leverage rather than just prying on the spring. This is the safest way to do it and avoids damaging any of the new parts upon reinstallation.

While the heads were at the machine shop our fingers did the walking through the Comp Cams catalog and we ordered up a complete valvetrain kit (PN K63-235-4) and a set of pushrods. The complete kit includes a cam, lifters, timing chain set, valvesprings, and valve stem seals all in one package. We went with the mid-level 260H cam with 110 degrees of lobe separation, 212 degrees of duration, 0.454-inch intake and exhaust valve lift. Now some might look at this cam and think we are over-camming it, but we’ve got no overdrive in the Jeep and are always in 4-Lo off-road anyway. Comp claims a near smooth idle which is exactly what we’ve come to expect from our little Dauntless powerhouse.

When they built Jeepsters, plastic was the next big thing. Unfortunately, it was also the new thing and plastic in automobiles and its interaction with automotive fluids was not thoroughly understood. We found plastic in various odd locations in this Jeep that had failed spectacularly, but a plastic-covered aluminum timing gear was a first for us. It was missing plastic and aluminum in two spots, and we are amazed that the engine still ran and the chain didn’t skip teeth.

If you are on a budget, a ridge reamer is another of those save-you-money kinds of tools. Before you go knocking the pistons out of the engine, take the ridge down with one of these and you will be much less likely to damage rings or piston. We borrowed this one, but over the years it had lost some critical springs for the cutting blade.

We ended up using our Performance Tools cylinder hone from Summit to knock the ridge down and hone the cylinder, but in the end it didn’t matter. We still ended up with a compression ring coming out in two pieces for cylinder number three and a crack at the wrist pin for cylinder five. Normally taking the ridge down will avoid these problems, so we suspect these issues were there before we took the pistons out. Interestingly, cylinder five also had a concave lifter lobe and a partially rounded-off cam lobe. We aren’t sure if that had anything to do with the crack, but there it is.

Before you knock the pistons out—heck, before you even loosen the connecting rod bolts or nuts—make sure to mark the rod caps and rods. They are machined together and need to go back together. We didn’t have a stamp set on hand, so we went with the old school multiple-dot method. The number of dots tells us which ones to match. And because we aren’t fools, we know to match dot-side of cap to dot-side of connecting rod. Make sure to keep your marks as far away from the joint to prevent any galling or metal deformation issues.

The best way to overbore an engine isn’t by hand with an inexpensive tool, but we started this rebuild with budget in mind. The best way is to drop the block off at the machine shop and let ’em rip. The next best way would have been to use a coarse stone to knock the ridges down and then a finer stone to clean it all up once we were within 0.003-inch of our 3.780-inch goal. However, as of this writing, the Performance Tool abrasives are only available in 220-grit. We’d rather have had 150-grit or so to knock the ridges down and 300-grit or finer for the finish. We used Rapid Tap cutting oil to lubricate and cool the stones, but engine oil also works in a pinch. We turned the pre-load up at the beginning to knock the ridges down and dialed it back down later.

The factory Dauntless bore is 3.750 inches and by the time we had all the ridges ground down the number three cylinder was at 3.770 inches (thanks to the broken ring). So we decided to go with a 0.030-inch overbore. Using the bore gauge from the rebuilder’s kit we were able to come up with the measurement. After boring a cylinder, it is possible that the cylinder walls aren’t parallel. That can lead to all kinds of nastiness from oil blow-by to busted rings. Much like our old high-school shop teacher would say, “Measure twice, cut once.” Don’t just go whole-hog with the boring tool, take your time and measure. Also, don’t measure just one spot in the cylinder. Measure the top, bottom, and center as well as a couple of spots in between.

As worn as the cylinder walls were, the crank bearings and connecting ring bearings looked surprisingly good and were within spec, so we were able to clean the crank up with some steel wool and install new bearings. We got the Clevite (PN CLE-MS960P) main bearings and Sealed Power (SLP-2500RAA) connecting rod bearings from Summit. We used Royal Purple assembly lube on everything.

Since the rebuilder’s kit came with a cam bearing installation and removal tool, we popped the $33 for the cam bearings (Sealed Power PN Z1205M). However, once we had the engine apart, our existing cam bearings were in fine shape. We originally used a flashlight to peer at the cam bearings, and the new cam felt good when we installed it. We were able to use this Harbor Freight LCD inspection camera for a better look and were able to verify the bearings looked good. It would have been better to measure them with a micrometer and feeler blocks, but we had no way to get an inside micrometer in there and no blocks with enough reach, so we’ll run it as is and return the bearings.

Body Chassis Transmission Drivetrain Electrical Engine Suspension Brakes Wheels Tires Tech QA

Rebuilding A Jeep Engine In The Driveway - Jp Magazine

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