F-Head Rebuild Questions

My F-Head will be torn into by a professional mechanic in the near future, and I want to be ready with information to make decisions based on what he finds. I am hoping the work is limited to the head/valves, but it might need a total rebuild.

Here are my initials questions:
1) Do most people increase the compression with a rebuild? If so, what parts?
2) If I need new parts, are there parts that are considered "better than OEM", such as cams with more/longer lift, different shaped pistons, better head gaskets, etc.?
3) I want a clean garage floor, so are there gaskets or other products/techniques that help prevent fluid leaks?
4) Any "gotchas" or advice in general for rebuilds?
5) Recommendations for rebuilds kits for head and bottom end?
6) Ignition upgrade suggestions?

Thanks in advance!

 

Hi John,


I do not have much info as far as the increase of compression and rebuild kits.

On my 58 I recently redid the HG, milled the head, cleaned the block, replaced rings, cleaned and new gasket on the oil pump, and adjusted intakes and exhausts on the way out, that was sufficient for my purposes. My journal bearings were OK so we reused em...good idea? Dunno but my rig doesn't go very far...or very often...

I got my engine rebuild gasket set at Walck's 4wd. I used blue RTV for my oil pan instead of a gasket. No leaks. My engine has .010 over pistons but there was a little more room than that in the cyls due to wear so we prepped the cyl walls bought .020 rings and eyeballed em, then filed down to get to within the recommended cold gaps.

I think if you (or your professional) do it right you wont have leaks at all, the leaks I suffer with are from the transfer case primarily.

Gotchas....? Hmmm there is a headbolt INSIDE the reservoir area under where the carb mounts! Be sure it comes out and goes back in!

Also, you can adjust the exhaust valves without removing the exhaust manifold so don't do that unless you really need to! When reinstalling the head bolts be sure all the sundries are in place so you don't get it all back together and realize OOPS forgot to mount the oil filter bracket....BTDT...

If you're painting the head, dimes are great for covering the bolt holes. a BIG time saver compared to tape!

If I think of more I'll let you know....

 

Matt - Thinks for the detailed reply. You raise an excellent point about miles not accumulating quickly in the future. Honestly, I think it will be a miracle if my Jeep ever sees another 1,000 miles on the ODO. Thus, minimizing the parts and labor expenses make sense. My reason for asking about better than OEM parts is that technology has improved so much since these motors were designed, I am thinking that if I need to replace parts, there might be some choices that are better than others. In particular, the F-Head was low compression (6.7 to 7.4), and with modern fuels, we should be able to run much higher (8.0 to 9.0?). I was thinking that higher compression pistons, higher lift cam, larger valves, and an electronic ignition, might really make a difference. However, in searching, all I find is generic parts.

 

"technology has improved so much since these motors were designed."

I might replace the the word "improved" with "changed". Think any new cars will still be around in sixty years AND still be the best of their type at what they do?

The F-head was built low compression for valid reasons, not from ignorance. And actually "new fuels" in fact are much lower octane than what I grew up with.

I've never had any problem with points ignition such that I couldn't make it home.

Some people might suggest hardened valve seats for your rebuild, but under low stress and limited miles I doubt it would matter.

A very early factory upgrade increased the oil flow to the timing gears. I think the FSM covers this.

 

Pete - I was not insulting the F-Head design or construction in any way. It has been my experience that with any product with such a loyal following as the Jeep, people typically find ways to improve things. I was expecting the same for the F-Head internals - improve pistons, cams, gaskets, etc.. Apparently this is not the case for the F-Head and the OEM products are the norm. This actually works in my favor as I won't be tempted to spend more money purchasing "improved' products that will likely end up causing issues down the road (there never is a free lunch).

 

No offense taken or meant. My experience with the F-head has been that standard shade tree rebuilds have not resulted in any disappointments. I don't think you need to worry, if careful work is done.

I think the consensus is that trying to soup-up an F-head is just putting lipstick on a pig. (A friendly and faithful pig.)

If there is an "improvement" I guess it would be the V6 engine, but I've never owned one. Off-road the F-head will get the job done.

 

Shade tree rebuild? How about leaky blue tarp rebuild. If you all remember, I rebuilt my F head this January, having only rebuilt a 1927 Buick engine before. It's with the help of this board (and no small part to the FSM & Walcks) that I was able to piece things back together. All while under a leaking Seattle sky - no garage space available.

Honestly, I think this "pig" is running beautifully. I'm getting wonderful performance and cruising right up to 52mph without any scary noises. All with oem parts. No need to search out the super charge kit, Holley carburetor, or even those performance head bolts. At least in my lowly opinion...

I've yet to be disappointed with my rebuild. Antique wiring? That's a different story all together ;-]

 

Only trouble with this is that my dad's VW Thing and my Karmann Ghia both run extremely rough on high octane gas. We tried running Super Unleaded at a previous mechanic's urging, and we were back on Regular within a month. I think its something other than octane that's making the gas perform differently.

Either that or the mechanic was advancing the spark well beyond factory spec, which he wasn't supposed to be doing.

 

The rings I installed (also from Walck's) are VERY different from what came out of my engine. So they are definitely "changed" I think the HG is of better quality materials too....but x2 everything 1962CJ5 said, except I can't get to 52 mph without the thing roaring like a lion....I need an OD!! I top out at about 45 and do not stay there very long!

I did my rebuild in a car tent in the back yard with a very knowledgeable friend for the cost of parts, cleaning solvents, engine paint & beer. Mostly it was cleaning! Lots and lots of internal and external grime. Just cleaning out the oil pan was worth the whole project!!

 

There is a lot of specific info on the F head at the 3B Page.



http://www.film.queensu.ca/CJ3B/Tech/KamunenEngine.html

http://www.film.queensu.ca/cj3b/Tech/EngineRebuilding.html

There was a high compression head factory option but trying to locate one is probably a futile task. The aftermarket parts era, for the most part, for the F head ended about 50 years ago. Clifford still makes a header for it.

http://www.cliffordperformance.net/...de=CP&Product_Code=57-0430&Category_Code=J258

All that said, you may gain 5 to 10 hp. I'm not sure if the lipstick on a pig is totally applicable, but if you want noteably more reliable power, an engine swap is the best path. The L 134 was a good design when it first appeared in 1926 and it did win Willys the WWII contract. It was already dated when the F head was grafted to it in 50-51 and, IMO, had far outlived its useful life by 1971.

 

If, as you say, your jeep is unlikely to see 1000 miles, it's probably not the best use of your time and money to try many upgrades. OEM parts will get you where you want to go. Really, just keeping it tuned up is huge with these engines.

Something mentioned time to time is what gas to use in these engines. Try some 100LL in it- 50/50 with regular. My F-head responded to that really well. In fact, once that tank was eventually drained from driving, I put in just regular non-ethanol. I could tell the difference- felt like 5-10 HP disappeared. When I get down halfway in the tank, I'll top off with avgas. Another nice thing about avgas is it does not deteriorate as regular does. Not a bad thing with a vehicle only driven a few miles/yr.

I agree with Duffer- try a swap if you really want to get more HP. I'd say the F-head outlived its design limits by the early 60s. If Kaiser had just used something like the Chevy 153....

Don't get me wrong- I love having an F-head in the fleet

 

The air cooled engines are very different to these - if you did not get 042 or 044 heads for those VW engines then the engine is designed to run on regular leaded gas. They can be ran on unleaded of course but it increases the temperature of the engine which results in it missing and not running as well.

Now, onto the Jeep F-head. I will start by saying unless you can either, get a very cheap deal on the parts or are set on keeping it original I would not rebuild the F-Head. You will easily spend $1,000+ on the rebuild and the engine will be outdated. But, that is definitely personal preference - I drive mine with the F-Head in it and my Jeep easily drives 60 MPH. But, I am in Texas on fairly flat land and my gears are probably different than your Jeeps - I do not have OD.

The thing with the F-Head is this, you can make a little more power but you will not notice it as much as you would think because the components are heavy and the stroke is long. In fact I find the easiest way to make your old Jeep have more pep is to have the flywheel lightened.

Aside from that there are a few things you can do, we got a F-Head up to 121 hp. Be warned that engine did tear itself up, definitely not recommended to do. I would say learn from others mistake on that deal. You can however get it up to around 80 hp by doing the following:

1) Milling the head around .20, but the mechanic will need a rough CC of the heads to determine the right amount. You want around 7.5-8.5 compression.
2) Electronic ignition - it makes a huge difference
3) A carb that is running correctly. The Weber conversion does make more power but you will find the Carter rebuilt is a good carb
4) Stock exhaust but cleaned up and wire brushed out in the inside so it does flow right. You could get a aftermarket header from Clifford's but it will cost you about $400 after delivery
5) 2.25 inch exhaust all the way back. Cliffords says 2.5 but from my experience the Jeep runs better on 2.25

Everything else stock and that will give you a dependable engine that runs near 80 hp and does not rev so fast it tears up. Still have to pay attention though with low gears

My two cents on new cars being built better - IMO the engines are definitely made better and will last longer if you get a modern iron block engine. I also think modern cars are made better but I don't think they are designed in a way to make them last. They are designed to last 200K miles and will do it easy. But, beyond that your just in for trouble with most of them.

The Jeep on the other hand was designed to last, despite what people often say. The designers had no idea how long the war would last or how long the Jeeps would stay in service so they designed the Jeep to be rebuild-able. If you ask me that gives them the edge over any new car and I suspect that is what PeteL was referring to.

 

" If you ask me that gives them the edge over any new car and I suspect that is what PeteL was referring to."

Yes, plus a lot of other stuff.

Flexibility and Drivability creeping over rocks or logs, OR on the road keeping up with a convoy. Capable of being massively overloaded and still pulling a trailer or howitzer. Able to power a ditch digger, generator, or a farm plow, and still go to town on Sunday. Operating anywhere from the Arctic to the Sahara, to high altitude, or completely underwater. Dependable reliability even in a combat zone. Field maintainable. Fair fuel economy. Digesting any grade or quality of available fuel. And so on. A very adaptable and forgiving power plant for a "Universal" vehicle. Okay, so no one uses the F-head for drag racing...I can live with that.

The proof is in the pudding - we are still happily using a engine born almost a century ago. The Zippo lighter or DC3 of off-road, on the trail it's as good as ever.

 

Well I am with PeteL. I drive my 63 all original.

I am toying with the idea of putting a Ford Ranger engine in it but I will keep the original engine of course. In fact I have two F-Head engines right now and access to two more. Both of mine run.

 

To add to what others have said: The BASIC problem with hopping up the 134 Jeep engines is that they have a LONG stroke in comparision to their bore diameter. That makes good torque at low speed but it severely limits the RPM that they can be operated at. In addition they're poorly balanced in comparision to more modern engines. The result is that even if you magically increase their HP you still can't drive the Jeep any faster without over reving the engine. The poor oiling system use in the 134 engines is something else to consider too. It would be dangerous to try to operating these engines at at higher speed due to the bypass oiling system even if you disregard everything else. AND another big factor is the shape of the Jeep body. It's basically a box with a big flat bill board (the windshield) sitting in top of it. Old Jeeps have horrible aerodynamics! And aerodynamic drag increases with the square of the speed and it would take a LOT more HP to overcome the increased drag in order to go faster. That's one of the big reasons why over drives aren't really much help in Jeeps, drag is the real limiting factor to increasing their speed.

You CAN increase the CR (compression ratio) relatively cheaply and easily but most folks have found that it didn't really gain them any power due to other engine design factors such as poor intake and exhaust design. Electronic ignition is almost always is a big help in old engines. Not because it increases the HP but because the old ignition systems didn't really stay in tune very long and would soon rob the engine of developing it's full potential HP. Electronic ignition systems stay in perfect tune with almost no maintenance and almost forever. A more modern cam design would probably be a big help but AFIK no one has made one. Others have already talked about headers and aftermarket carburators. I'll just say that I completely agree with them that you're better off sticking with the originals. Just make sure the carburator is adjusted correctly. Hardened valve seats won't get you any more HP but they MAY make the engine last longer. These engines were designed to operate on leaded gasoline and one of the purposes of the lead was to keep the red hot exhaust valve from trying to weld itself to the valve seat every time that it closed. Since they've taken the lead out of the gasoline, hardened valve seats are mandatory IMO. A broken valve can do a LOT of damage to an engine and hardened valve seats are cheap in comparision! Other than that, you just have to go with the basics: make sure the cylinders are honed correctly and not tapered or out of round so that you don't lose what little compression Jeep have. Make sure that the rings are gapped right and the gaps are off set from each other. Make sure that all the little things such as the counter weights in the distributor are free and operating correctly. You'd be surprised at how many stories I hear of people converting their distributors to electronic ignition because of poor performance but then when they gut the distributor to modify it, they find that the counter weights haven't been cleaned or lubed in YEARS and were frozen and wouldn't move!

Regarding gaskets, a friend of mine is a GREAT mechanic and he swears by the Fel_Pro gaskets. He says that most gaskets will crush after a bit and will cause the head bolts, valve covers, timing chain covers, etc to loosen up and they will need to be retorqued after running for a bit. He says that the Fel_Pro gaskets don't do that and thus eliminate the need to retorque all the bolts. That was on more modern engines so I don't know if it applies to Jeeps or if Fel_Pro even makes gaskets for Jeeps but it's something that you might want to think about.

 

"Since they've taken the lead out of the gasoline, hardened valve seats are mandatory IMO."

I know we all worried when that happened, but since then has anyone actually had a valve problem definitely caused by unleaded fuel? (...In an 'antique' low performance engine.)
I don't personally know of anyone who has.

 

Absolutely. I don't know of it ever happening to a Jeep engine but it has definitely been proven to be an issue with other old engines.

 

"but it has definitely been proven to be an issue with other old engines."

I'm curious if you've seen it personally, or what your source is? I have a bunch of antique vehicles, never met anyone with an "unleaded" valve problem.

 

I have seen it personally and it is documented. Read about VW bug engines that have not been converted, it is common for them to have valve problems running unleaded, it is also common for them to over heat running unleaded gas