Adapting an F134 head to an L134 block

[Nemo von Klepper]

After finding cracks in my F134 block, the gears in my head started turning to figure out what my options are. I noticed that the L134 and F134 are so similar that they share a huge number of parts. I can find a replica L134 block to build and I even noticed that the head taps seem to be in identical locations to the F block. It got me to wondering if an L block can be milled and adapted to accept an F head. Apparently the answer is “yes”.
https://www.jalopyjournal.com/forum/threads/willys-l-head-to-f-head-engiine-swap.576654/

There isn’t a lot of info in that post, but most of it went along the lines of the way I was thinking. There’s some explanations I find confusing, maybe swapping the intake side? Or maybe converting an F to L?

Anyway I thought this might be a good conversation starter. Has anyone done a conversion like this?

[gmwillys]

The article is a bit confusing, but also has a lot of good information as well. I learned a lot from it that I have had yet to study.

The biggest hurdle would be that the L head has the intake valves in the block. With that being said, the passage would have to be milled to allow a push rod to travel through the block and head to operate the rocker. Not impossible in theory since the push rod doesn't make contact with anything other than the lifter and the rocker. The cam configuration would have to be swapped due to the opposite rotation of the F head can. The F head has one mount hole within the intake that does not line up, but can be reworked to fit, but requires welding the cast iron.

In my opinion, I would hold off until the F head version of the reproduction block come on to the market. It shouldn't be too long now, since the L head block has been on the market for a year now.

[Nemo von Klepper]

"Like"

So according to the post I referenced, which sort of confirmed what I was thinking, the push rod ports line up exactly with the intake valve ports. The reason you can't just put the F head on the L block is that you won't get a good gasket seal on the account of the intake valve seats. There was mention of having disks milled with holes in the center that would be set into the valve ports like a hardened valve seats. There was also mention of needing to grind the L camshaft to F specs. I have an F camshaft, so that step would be unnecessary.

What I'm wondering about now is if all of the water jackets line up. This was the real reason I did the web search.

[Nemo von Klepper]

Disregard the wonderings about the water jackets. They seem to be a perfect match.

40594060

I'm satisfied that this is a reasonable project. If I find myself in need of building a new engine I think this is doable, I'd just check with an engine shop first to see about their opinion about pressing push rod adapter disks into the L intake ports.

[gmwillys]

It would be a worth while project to follow along with. It will be interesting to learn what the machine shop has to say.

[Nemo von Klepper]

Yeah, anyway, according to the post in the other forum this wasn't that unheard of, to put an F head on an L block. I think it could also be interesting to contact Kaiser Willys about this idea. It might not be such a big deal to market an adapter kit for their L block; anyway, cheaper than setting up the tooling for an F block, for whomever produces their L block.

I'm going to see about getting my cracked block going again, but I feel a bit better about options being out there. I was getting a bit uneasy about sinking much more money into my rig if getting a good original engine was going to be challenging.

[gmwillys]

The L head block is being marketed by an avid collector that saw a need to come up with an alternative to digging through piles of blocks to maybe come up with a viable option for rebuild. He put out for bids from some small U.S. based foundries using CNC mapped modern alloy blocks. When the bids came in, it turned out that the costs were much higher than the average restorer could afford. From there, the bids were put out to some foreign foundries for a price comparison. An outfit out of India,( if I remember correctly) came through with a as specified quality allloy block, as seen offered by Kaiser Willys. If I read between the lines, it looks that KW is either an investor, or the lone distributor of the blocks. Mike put out an answer to the question to when a F134 reproduction would be available. His answer was that hopefully by the end of the year.
With all that being said, this isn't to discourage your idea. We are all about having options to go to. There is always more than one way to do the job.

[Nemo von Klepper]

Great to know! I hadn’t contacted Mike about an F block yet. I was doing the leg work to see what my options were. If I manage to get my present engine running satisfactorily then I don’t imagine I’ll be building an engine right away and I’ll be able to wait. If it’s toast, then building an engine will be the next thing on my list.

The CJB seems to be a little bit of an ugly duckling. It’s not my first choice, it’s what my mom gave me. She bought it in a fit of nostalgia before she realized it had a long way to go to be road worthy. She learned to drive on what I believe was either a CJ2 or 3a on a farm back in the ‘50s.

Anyway if I suddenly got it into my head to buy another Jeep, I’d probably do an MB, CJ2 or 3a. I like their looks just a tad better. Fiddling around with the 3B however and it’s starting to grow on me.

[gmwillys]

The 3B is a bit of an ugly duckling, but as the market decreases in the availability of the MB,2A, and the 3As, people are starting to get into the 3Bs. It is a good platform for installing an unlimited engine options. The same can be said with the Jeepster Commando. Tastes change, and I would love to find a Commando Hurst addition.