CJ L-134 Engine Disassembly - NEW VALVE QUESTIONS (3/29)

[dtgolder]

Going to post my findings as I disassemble my engine (as part of my ongoing project)...

So far so good today--nothing crazy, but a few questions:

1) I'm misisng the tube that goes from the main bearing cap into the sump. Not sure what the purpose of this is, nor if it's necessary to replace it.

If I do need it, anyone have any idea who might suppy this? And is it just a press fit, or is there some kind of a retension mechanism? (I'd be a bit worried if it's just a press fit that it could work itself loose and drop into the pan, which perhaps is why it's not there?) I also don't see this in my parts manual...

Thinking this would only serve to funnel oil from the main bearing into the sump? So if it's missing, wouldn't the oil just go into the sump anyway?

2) I measured camshaft end play at 20 thou...and spec is 4 to 7 thou...

I haven't taken the cam out yet, but the manual seems to indicate that the end play is the difference between the thickness of the spacer minus the thickness of the thrust plate. Right now, I'm thinking maybe the camshaft gear or thrust plate hasn't been tightened to spec (probably the thrust plate?).

Thrust plate: 20-26 ft lb
Camshaft gear: 30-40 ft lb

3) Cam gear and crank timing gear seem to be in good condition. Are these re-usable or is it best practice to just replace them? (Particularly the cam gear as it is some kind of composite...?)

4) I do have Pal nuts on the rod bolts. Are these even needed? If so, are they re-usable, or is it best practice to buy new ones?

Think that's all for today--going to dig in more tomorrow.

One comment is it was virtually impossible to see the timing mark on the cam pulley that matches up to the crank pulley--I had to line the gears up to where the mark should have been, and then clean and check very carefully, and finally I could see it. Maybe it's more visible on a new cam gear, but even now when I know where it is, it's nearly invisible.

 

[HawaiianCJ]

Hi D-
I can address these since Iʻve been reassembling my motor and everything is still fresh.
1. My rear main cap has the tube- Itʻs a drain back for the seal area. I donʻt think itʻs really necessary, just a little extra insurance. Just for infoʻs sake, the tube has a drilling in one end to match up with the small hole in the cap. The tube plugs into the cap and a split pin goes into the small hole to hold the tube in the cap.
2. Cam end play is kind of trial and error. The spacer is supposed to be slightly thicker (.006”) than the thrust plate to give end play in the specified range. Even with a new plate and spacer I didnʻt have any end play. I used .005 shim brass to make a shim that gave me .004” end play when everything was tightened to spec.
3. Gears are reusable if the wear isnʻt excessive. There is a spec for gear lash (.002”, I think) but if it feels OK it probably is. Just be careful pulling the cam gear- itʻll break pretty easily.
4. My motor didnʻt have the pal nuts and the nuts were tight but since I had to replace the hardware anyway I went ahead and added them on reassembly. The manual says they are one-use only- replace them if you want to use them. Cheap insurance?
Hope this helps.
Tim

 

[JABJEEP]

I had one that didn't have the tube, or a hole for it. I had another one that was missing the tube so I made one by copying another one I had. I think it was 1/2" soft steel tubing.

I never had cam play that was out of spec and I had some pretty worn engines. Crank endplay is a whole 'nuther matter because every time you step on the clutch you stress the thrust bearing (#1 main) that sets crank end play. Seems odd that they let the entire crank take that load insted of having the thrust adjustment set at the rear.

I learned to never remove the sprocket unless you're going to replace it. There's no need to remove for any other reason and they often break if you don't do it properly. They're better off being removed after the camshaft is out.

I use new Pal nuts, most people don't use them at all. You should not re-use them. Most people use a loc-tite product now instead. Remember as you're torquing that the loc-tite product acts as a lubricant (when uncured) and reduce torque accordingly.

 

[1955cj-5]

When an engine runs there is a certain amount of blow-by, which creates a positive pressure in the crankcase.

The PCV valve and associated plumbing is there to ventilate this pressure to a vacuum source, typically the intake manifold.

Some engines like the MGA, used a draft tube. When the car was moving the air flow across the end of the tube would create a low pressure helping to ventilate the crankcase. The Bugeye Sprite might of had a similar tube.

In early engines, without the PCV valve and plumbing, positive pressure in the crankcase would try to force the engine oil out any where it could. The rear main was a favorite.

The Go-Devil L-134 had both a PCV valve and a line from the oil filler tube to the intake crossover tube which would draw the crankcase fumes into the carburetor.

The rear main cap tube, leading from the rear main bearing cap to below the surface of the engine oil in the sump, was meant to allow oil drainage from the cap without allowing the crankcase pressure to force it out the back of the engine and onto the floor, with moderate success.....many early engines didn't have much of a rear seal, if any. The MGA used a reverse scroll to try and force the oil back into the engine.

Class dismissed.

 

[1955cj-5]

?

 

[1955cj-5]

Remember, the oil enters the rear cap at some 60 PSI, so if it is prevented from draining into the sump by crankcase pressure it will find another exit.....

 

[Rastus]

If it's a fibre gear replace it.

 

[dtgolder]

The rear main cap tube, leading from the rear main bearing cap to below the surface of the engine oil in the sump, was meant to allow oil drainage from the cap without allowing the crankcase pressure to force it out the back of the engine and onto the floor, with moderate success.....

Ok, that's the key item I was missing

I didn't realize the tube was beneath the (anticipated) oil level in the sump...and I have to say I keep leaning towards putting in the valve cover with the tube vent in it and skipping the PCV and sump pressure issues entirely...

But if not I likely will need to find a tube for the rear main cap...

Regardless, thanks for the explanation and the "missing link" here in my understanding.

 

[dtgolder]

One additional thought here...(and a point of confusion for me).

There is a tube connecting the dipstick tube to the air intake...my understanding is that this is to provide filtered air into the crankcase (and that air will eventually make its way to the carb via the PCV valve when engine vacuum is low enough to open the PCV valve).

But why can't excess air pressure (e.g. blowby) EXIT that tube (just like it can from a tube on the valve cover)? In fact, my tube is currently not connected to the crossover tube (I'm going to try and run without that, as I'm using a K&N on the carb).

If the whole point here is to vent excess pressure out of the crankcase, why can't that vent be out the dipstick tube? (Yes, it's dirty air, and pollutes more than it should...but why wouldn't that work?)

 

[1955cj-5]

There is a tube connecting the dipstick tube to the air intake...my understanding is that this is to provide filtered air into the crankcase

When the engine is running the dirty air will be sucked out of the crankcase and into the carb. If enough pressure builds internally to force the crankcase air out you might get some oil with it.

The MGA engine like many others has a vent tube from the valve cover that routes to the air cleaner, so it too is pulled into the carb.

 

[dtgolder]

The MGA engine like many others has a vent tube from the valve cover that routes to the air cleaner, so it too is pulled into the carb.

Huh--forgot about that (my Mini had a finned aluminum cover, with the tube, and my Sprite has a custom filter housing incorporating stub stacks (so no provision for the tube) but I do have a couple of old valve covers with those...) And of course have the vented downtube from the side covers...

Have a lot of fond memories of time in an MGA...used to greatly enjoy "blipping" the throttle at stop lights from the passenger compartment (to the total embarrassment of my friend in the driver's seat). Probably the best "feature" ever on the MGA...

 

[1955cj-5]

Have a lot of fond memories of time in an MGA...used to greatly enjoy "blipping" the throttle at stop lights from the passenger compartment (to the total embarrassment of my friend in the driver's seat). Probably the best "feature" ever on the MGA...

Only on the LHD models!Pretty funny though. I've never had anyone do that on purpose...


(there is a crossover rod from the accelerator pedal, across the transmission tunnel, into the pax footwell where it connects to a cable and then to the carbs.....designed as a RHD car so this is for LHD only)

 

[dtgolder]

I've never had anyone do that on purpose...

Well, it provided me with endless hours of entertainment...ESPECIALLY when a Vette or GTO or something similar was next to us.

 

[1955cj-5]

ESPECIALLY when a Vette or GTO or something similar was next to us

Scared 'em pretty bad I bet...

 

[dtgolder]

To summarize yesterday (i.e. notes for myself):

• Get new Pal nuts
• See if I can find a tube for the main shell
• Revisit Cam endplay when I pull the cam
• Buy a new fiber cam gear

UPDATES (and questions) FOR TODAY (Thursday March 26, 2026)

1) Oil Pickup - This seems to be held on by just a cotter pin(!) and if you don't have exactly the right size, it'll come off...(easily). Is that correct? Just a cotter pin? AND - there's no o-ring or anything to seal this, although it does seem like there's a groove to perhaps contain an o-ring? (i.e. do I need to find an appropriate o-ring for this during install?



2) Rod Bearings - in general I was quite pleased with the rod bearings and journals. I'll check again tomorrow very closely, but I didn't find any scoring, and just some mild staining (i.e. I fully expect these can just be polished out). I'm hoping the mains are in as good a shape. HOWEVER, it seems (see bearing picture below) that the rod bearings are 30 under? (If someone could help decipher the bearing codes I'd greatly appreciate it). If so, it seems that's the limit of what I can grind the crank to according to the manual--so if it can't be polished...well am I looking at a new crank then?





3) Rods - all seemed ok, except #1 which was really hard to remove. I had to tap out the rod from the cap. Once removed, all the other caps slid on easily, but #1 couldn't be put together by hand (I'm sure I could put it on by tightening the nuts but...) So I suspect either the bolts have stretched / moved or the rod is stretched (widened). If so, I may need a new rod? Anyone have any thoughts? I'll certainly ask the machine shop to check all the rods to see if they're in spec...Interesting that the other 3 rods are "matched" as they'e stanped as pairs, but there are no stamping on #1...



4) Hardware - should I be looking to buy new rod bolts and nuts? (I was originally thinking I could reuse this hardware, as well as the wrist pin bolts). Are those something that I need to add to my shopping list?

5) Crank Timing Gear - This gear has (thankfully) two threaded holes in it--I ran some bolts in...and I was hoping that if I continued to simply tighten them they would ease the gear off the crank...but before I put any significant pressure on that, I wanted to ask the group whether that's a good idea? If not, I should be able to rig up some type of puller to use those bolts to pull that gear off...



6) Broken Ring - lastly when I pulled #3 there was a broken first (compression) ring...which was what I expected to find, given the damage in #3 cylinder and the history of a seized motor (see this thread for details). Lots of carbon around all the rings on all the pistons, but all the other rings were free, and moving quite nicely...just this one ring...

7) Clutch - and one other aside, when I pulled the engine i did notice the clutch was pretty close to the rivets...so even if pulling the engine was a pain, I'd likley have had to do it fairly soon to replace the clutch.

8) Crank Endplay - oh--did a quick check of crank end play (going to see if I can get a better reading tomorrow) but it looks like I'm at 8 thou (spec is 4 to 6) so not too far off...will see what kind of shims I have in place once I get the front gear off...

Appreciate any and all comments, suggestions, thoughts, recommendations...

 

[JABJEEP]

1). yes, just the cotter pin. The joint is below the oil level so it's "sealed" by the oil.

2). let your machine shop guide you there. Whether the crank can simply be polished or not, you'll be replacing the bearings.

3). again, use the experience of your machine shop. They will weigh it, examine it, compare it to the others, etc. and guide you.

4). I have re-used them, and replaced them, depending on the condition of the engine and how things look overall. Again, your machine shop will have an opinion.

5). don't use those bolts to push. Use them to attach a puller and push on the crank with some sort of protection for the end of the crank and threads.

6). you'll be replacing all the rings.

7). good call

8). that will change with the new crank bearings and you will adjust it (shims) then.

 

[Oldpappy]

I have several random piston/rod assemblies. Let me know if you need one or two and I'll check what I have.

 

[Rastus]

He'll be replacing rings & bearings to fit correctly, having rods re-sized so the bearings fit in them properly with good crush & shell back contact & if not being bored he will remove the ring ridge from each cylinder or have broken rings again.
All rings must be fitted, gap measured & adjusted as necessary 0.003" per " of bore diameter @ the bottom of the cylinder it will be working in.
A dot or TOP on the ring is most important.
The slot in the piston is on the opposite side to the oil spray hole & toward the camshaft.
Don't forget the rods when fitted to the pistons then the crank MUST be central on the piston pin = space either side of the centre.

 

[dtgolder]

He'll be replacing rings & bearings to fit correctly, having rods re-sized so the bearings fit in them properly with good crush & shell back contact & if not being bored he will remove the ring ridge from each cylinder or have broken rings again.
All rings must be fitted, gap measured & adjusted as necessary 0.003" per " of bore diameter @ the bottom of the cylinder it will be working in.
A dot or TOP on the ring is most important.
The slot in the piston is on the opposite side to the oil spray hole & toward the camshaft.
Don't forget the rods when fitted to the pistons then the crank MUST be central on the piston pin = space either side of the centre.

Very little ridge on the cylinders (mostly carbon). Ring was broken from being seized I believe...

I think I understand what you mean by "the rods when fitted to the pistons then the crank MUST be central on the piston pin = space either side of the centre" but let me check--are you saying that the piston fit in the bore needs to be centered over each rod journal (so that the piston rides "true" in each bore)? If so, then isn't this dependent upon the crank grind? (i.e. if this is off, I'm not sure how I'd adjust this or correct it?) Or are you talking about the "narrow side" of each rod being next to the nearest main?

 

[Rastus]

It means the rod's are fitted right way round.
The rods are 2 x 2 if fitted. Incorrectly & the rods will run off centre in the bore & this will be evident by the rod not being central on the gudgeon pin.
No ridge @ all. It must be fully removed properly & not over removed. New rings 120* apart [never central on thrust face} [particularly the top] can break for a number of reasons
1. Not cleaning the ring grooves out properly on previously used pistons
2. too little ring gap
3. ring ridge
4. poor installation
5. over advanced ignition timing [pinging/pinking]
These are pretty good guys to follow doesn't matter L or F heads engines. Not sure if all is correct as I did not watch them right through. Lew has a series of engine assy. videos so sort through & find them all.
I hate seeing dirty benches when folk are assembling engines & the 2nd one shows more of this. It doesn't take much to introduce dirt into ones fresh rebuild.
& I always have a can of clean oil to dunk the piston & rings in prior to fitting to the bore. It's messy but a good practice.
If they don't mention checking rod for twist, one should do that. Plus fitting plastic tube over the con rod bolts so the polished crank is not damaged when assembling.
I don't like the sandal type safety shoes in a later video I just looked @.