The CJ3A Engine

February 6th, 2015

This page highlights efforts to fire up an untested Jeep Willys L134 four cylinder flathead engine. This engine was purchased to put into a 1950 CJ3A. To find out about the CJ3A, go here: The CJ3A Introduction Page.

Jeep L134 Flathead Engine Testing

Willys L134 Jeep engineIn 2009, I was looking on Craiglist for an engine for my CJ3A and I found an ad for a good candidate that was pretty local to me. I went for a visit and found the seller to be a young fellow with a serious Willys Jeep affliction. He had Jeeps, engines and parts all over the woods in his backyard. 

He used a pine tree as his engine hoist and the engine I was interested was hanging in the tree. I was a little hesitant about buying an engine hanging in a tree, but then the dad meandered over and started throwing in extra parts in order to make the sale. I think he mostly wanted to clean up his backyard. So, with an exhaust, generators, and springs thrown into the deal, I bought it.

Willys L134 Jeep engine 641087 The engine has a casting number of 641087, but curiously the last 4 digits were ground off and then stamped with the "1087" And the stamps look old. The engine was promptly put away in a corner while I worked on other projects, and years have passed.

But recently, the Jeep whisperings have been bubbling to the surface of my brain, and a window of time has opened up at Squids Fab Shop. It was time to get busy on the Jeep. I had never test run the engine, and I wanted to hear it run, so the engine was pulled out from it's dusty corner to begin work.

Willys L134 engine standA crude engine stand was my first mission. A cart was fashioned with some lumber and casters. Old scrap steel was employed to adapt the motor mounts and bellhousing to the cart. More scrap steel was used to position the CJ radiator and shroud in front of the engine to take advantage of the cooling fan. A small panel was made to hold water and oil gauges, as well as switches for the ignition and charging system (not shown yet.) Note how previous owner did some custom stenciling on the side of the block. Also note the head is not the same....keep reading below....

Bypass Oil Filter System

External Fram bypass oil filter for Willys L134 engineWith the "stand" ready, the engine systems were next: The old Jeep flathead engines (like many engines in those days) used externally mounted oil filters, and I was missing many parts. I sourced the external oil lines from, but saved some dough by getting the hard-to-find flare fittings at a local hydraulic supply company. (It pays to search around...there can be huge variations in costs across suppliers, both local and online.

Broken head stud Willys Flathead 134 on 1950 CJ3AInstalling a new oil filter mount disturbed a few of the head studs/nuts, necessatating a re-torquing. Unfortunately one of the head studs broke while approaching the torque value. So off came the head in order to drill out the offending stud. While certainly a bummer, it did allow an inspection of the pistons, cylinder walls and valves. The good news is that it's in pretty decent shape and in fact still has standard bore pistons. 

Industrial Willys L134 head before sandblastingIt seems that a crack in the head gasket allowed gases to erode the stud which weakened it. I managed to drill out and remove the stud without damaging the original threads in the block. I sourced some Dorman head studs p/n 675-013 from Amazon (sometimes you can get Dorman stuff on Amazon for extremely good prices...woot) and switched to my blasted and cleaned "INDUSTRIAL" head from the seized engine that came in the Jeep. (The head I removed was riddled with cracks). I also inspected the tappets, and removed the intake exhaust manifold which in turn required me to source new manifold studs. I got those, shockingly enough, on a twirly rack at a Pepboys.

Charging System

The original CJ Willys charging system was a 6 volt generator with an external regulator. The components on the Jeep have long been dormant and likely corroded beyond usefulness so I decided to "upgrade" to a modern (well, 80's vintage) Delco 12si 3 wire alternator. 

Jeep Willys Alternator swap CJ3a flatfenderThe Delco alternator has internally regulated 12V output, it's cheap, super reliable, and easy to use. The 12si is probably the ultimate unit to look for (better internal cooling according to my research), but the 10si's are fine as well. The P/N I sourced is for a 1980 Camaro application.

A minor glitch when using a modern alternator is the relatively narrow pulley that does not work well with the very wide "V" belt the L134 crank and waterpump use. There are suppliers that sell wide "tractor" type pulleys, or you can chuck the narrow pulley in a lathe and machine the "V" groove wider.

CJ3a alternator conversion bracket Willys L134Adapting a modern alternator to the little flathead requires a custom bracket which can be had from some Jeep specialists online, but it's easy to fabricate your own. My little box of scrap metal yielded enough bits and pieces to weld one up. It's fairly thick steel so I used a propane torch to preheat the metal for better penetration.

Last thing to do was to replace the cap, rotor and ignition wires. I figured the rest should be okay since it was advertised as running when I bought it. At the first start attempt, cranking speed was normal, but there was no sign of a pop. A test for spark (with a removed spark plug) was positive, but there was no ignition when installed. I put in a new coil, and still nothing. I replaced the points, and bingo! Instant ignition. A few leaks were attended to, and a few minutes of run time indicated a dirty carburetor. The solex carb has a bunch of plugs and caps that can be removed to access internal passages. I removed all of them and blasted everything I could with carb spray cleaner. A dramatic improvement to idle quality was observed and after a little warmup, it revved nicely too. There is a bit of blue smoke I think from leaky valve guides, but this little flathead is a decent runner.

I made up a low quality phone video of the running engine:

To see the Willys Jeep CJ3A drivetrain rebuild, click here!



Jeep Forward Control "Mighty FC"

Here's a really cool something Jeep engineers and marketing people came up with that they will never build. I'd buy a Jeep pickup if they would just make one. Oh well. Above is a link to an FC concept hype-mobile.

Here's another cool Jeep Pickup concept from about 2012:

1967 GTO Original Owner

These two videos feature an original owner GTO. This car was featured in Hemmings Muscle Cars magazine a couple years ago. Part 2 has inside and outside shots of the owner driving the car. Very nicely done.

Blues Maker

"Mississippi" Fred McDowell. One of the great Bluesman. This is a documentary made in 1969.


Pinstriping the ol' fashioned way. Pretty nice.

Blues Traveler. Wow.

Blues Traveler plays often on the Dave Letterman show. Here they are playing a toe tapper with Paul Schaffer.

Pepsi Throwback

Pepsi Throwback with Sugar!

Pepsi has put out a "limited edition Throwback" version of Pepsi with REAL sugar, instead of high fructose corn syrup which has been used since the 80's. Holy cow there IS a difference; it's WAY better. Find some quick!

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