L18 Cam Tensioner?

[610StaWag]

1973 Datsun with L18. Ran perfectly for 20 years. Not driven for the last 10 years. Won’t run now. Compression: #1) 150,  #2) 65,  #3) 147,  #4) 65. (oil in cylinders 2&4 does not increase the compression numbers)

 

When in front of the car (with the cam cover off), and I turn the engine by hand, the cam belt/chain is loose on the right side, then there is a clank/click and the belt is tight. I continue to turn and the belt goes slack. Looking down with a flashlight, I can see a small movement (towards the right) on the left side of the belt, when I hear the clank (I assume that this is the tensioner pushing on the belt). When this happens, the belt becomes tight. I assume that when the belt is slack this is messing up the valve timing.

 

I hear horror stories of problems replacing the tensioner.  My questions:

1) Do you think that all I need to do is to replace the tensioner?

2) Do you think I have to replace anything else?

3) Can a very average guy do this? I have worked on a few engines, including a 100% rebuilding of a 1.1 German Opel engine, all my experience is with OHV. I am intimidated by OHC.

4) I asked one mechanic how much to do this and he said a complete repair to the tensioner and guides with a new belt would cost at least $1,000 for labor and new parts.

5) What is the price range for a used engine?

6) What is the price range for a rebuilt long block?

[kgrantkey]

Your gonna need a new chain probably.  I took some pictures when I was rebuilding my l20 and the slack was so much the cam tensioner would almost come out of the cylinder with the spring behind it. Some even remarked it looked like I was trying to put a l20 chain on an l18 motor.

 

 No telling how many miles the chain had but when I got my new l20 chain it was much smaller, same amnt of links tho. 144 or something like that. It made a big difference. I wouldn't pay 1000 dollars to the best mechanic in the world to fix your problem. If you have ever pulled the head off an L motor you can probably fix this yourself. It may take a little time pulling the engine&Tranny out to freshen up some stuff or just remove radiator and anything in the way.  One reason I love my 620 is because its so simple to keep running.

 

OHC is as easy as OHV too me IMHO unless your talking double overhead cam. But your not.

 

Good luck.

[banzai510(hainz)]

this is freehttps://vimeo.com/19077890

 

Tools might be more for a good set

 

 

clean gas tank?????? rust??? drain maybe

 

you ck the vavlve lash pads to make sure they are adjusted so they are not tight and letting compreesion out or letting air in.?????? or just plan fell out.

 

 

you turning the crank clock wise???????best to do that.

 

 

you can ck the cam timming and if good it should still run even with a worn tensioner I think as the cahin will be tight a its running

 

most time you can just replace the slack side guide and then tensioner.

[datzenmike]

If you are turning the engine by turning the cam sprocket you will get slack on the driver's side. Engine crankshaft has to turn the cam. This pulls down on the driver's side of the chain and why it's called the tension side. All the slack is then on the passenger side. If turning the engine, use the crank pulley bolt.

[610StaWag]

Yesterday I had been hand turning the engine counter-clockwise (but not by turning the cam sprocket), and I got the slack and then tight chain. Today I used a wrench on the crank pulley bolt clockwise, and the chain did not go slack (well very, very barely slack. I could deflect the chain barely a 1/32" on the drivers side).

 

I took a large screw driver and used the palm of my hand to tap hard on each valve stem end/spring cap when that valve was not engaged by a cam lobe. I rotated the engine so I could check every valve. Every one opened and shut with a click sound. Some maybe leaking, but none are stuck open.

 

It seems odd to me that #2 and #4 are both at 65.

 

I went through the posts and video from 2011. It isn't as scary now to think about rebuilding the camdrive. I did find an ebay seller with a complete kit (made in Japan) for $89 and free shipping. But now I am beginning to wonder if the cam drive is really the problem.

 

You guys sure know more than I do, so, what should I do now?

[banzai510(hainz)]

this is what I do. if no basic tools on the cam.

 

I rotate the motor till a cam lobe is pointing up and I take my fingers and wiggle the rocker arm. If it wiggles I know the valve is closed. If lobe and and its tight then I need to adjust the rocker arm by loosen the 17mm jam nut then take a 14mm open end and adjust the post down to fit a feeler guage in there. around .008 .010 should be enough. If you cant get the post down anymore that means the valve is sunk and needs to be rebuilt or swap head(ezer)

aIt can be a cracked valve or valve seat or piston crack or rings busted ect....

 

 

I went through the posts and video from 2011. It isn't as scary now to think about rebuilding the camdrive.

 

Just do 15 mins a day and use Ratsun and you can get thru it.

[datzenmike]

The engine may have sat for 10 years with #2 and #4 valves open. They just got rusty and are not sealing.

 

Rotate the engine to the compression stroke on #2 and then #4 and remove the rocker arms. Set the engine at TDC any TDC on #1 then rotate 90 degrees. This puts all the pistons half way down the cylinder and safely out of the way of the valves. Get a 'soft' hammer (I don't know what they are called) and tap the valve spring hard enough to depress the valves on 2 and 4. Do multiple times.They will snap shut with great authority. Any minor rust will be rubbed off and the face will seat.  Re assemble and get it fired up, the valves will polish themselves from running. If this doesn't work, you may need to remove the head and lap or replace the valves.

[610StaWag]

Thank you hainz and datzenmike (and everyone else), I will do both your suggestions.  I guess. I will look for my feeler gauges and then do that rocker removal. I have a rubber mallet (too soft I guess), a rawhide mallet and a hard plastic mallet to hit with.  I do better work when I don't rush, so I may be awhile until I get to it again.

[datzenmike]

A heavy rubber mallet will be best. This will momentarily open the valve and it will slam closed... hopefully sealing better. Driving should improve the seal. If not it was worth a try.

[610StaWag]

I am unsure about the correct way to remove the rockers on this OHC engine. It was easy to release the mousetrap spring but what now? I saw a video and a guy used half of a large channel locks to pry the camshaft up to have room to pull the rocker out. Seems wrong to me. Does the camshaft have to removed? All the other videos I saw had shown the camshaft being removed. If so, that is far beyond what I can do. My left hand is disabled and so is my income. Do you think anyone would be interested in a 1973 610 station wagon that doesn't run? Do I try to sell it/give it to an auto wrecker? I had spent many months on bodywork restoration (prior to my hand situation), the car is now in catalyzed gray primer. I have all the trim and a couple of good looking replacement taillights. 

[banzai510(hainz)]

turn the rocker arm post down far as it can and then use a screw driver to push the valave retanier down to get the rocket to jump out.

of caosrse the lobe must be pointing staright up

 

 

give it to a Datsun guy who MIGHT want it if you cant handle this

 

 

Do you think anyone would be interested in a 1973 610 station wagon that doesn't run?

 

 

YES!!!!!!!!!

[610StaWag]

Thanks for the tips. I am beginning the project. 

1) Is it OK to pry the rocker out on the rocker arm post side instead of the valve spring side? I got one out prying the post end.It was a lot easier than trying to pry the valve end.

2) There is a very slight indentation on the rocker where the cam lobe contacts it (about .0001 I guess), is this normal?

3) I can't remember (where to find the tip/videos)  the order to work on the valves that requires the least amount of turning the camshaft. Does anyone remember this?

4) Can I turn the cam via the camshaft bolt? Does it matter here if I go clockwise or counter-clockwise?

[datzenmike]

If the timing chain is on I would turn the engine by the large crankshaft bolt.

 

Turn the engine until TDC on the timing scale pointer. This will allow half the valves to be closed and the rockers easy to pry out. Turn the engine ONE complete turn and bring to TDC and you can remove the other 4 rockers. As mentioned only the arms that don't have a cam lobe pushing down on them can be removed. Do not pry on the cam lobes, only the spaces between.

 

The slight wear you see may be from using today's oils that have reduced ZDDP in them. I run Shell RotellaT 15W40. (Chevron Dello 400 is also good) This is a light diesel oil with lots of scuff resistant ZDDP in it. If the scuffing is extremely minor you can wet sand it out with fine (1000 grit? wet paper using a sheet of glass in the sink) Research this

[610StaWag]

Thank you, and yes, cam lobes are never to be used to pry. I understand your procedure of doing four, and after 360 degrees, doing the other four. I know it may seem a bit silly to skilled mechanics, but I am interested in the sequence of valves that are at maximum closure. It looks like Intake of #3 is nearly at complete/max closure, i.e., the cam lob is nearly straight up. I know that I could figure this out myself, but it would take me a long time. Does anyone out there know the sequence of valves that have cam lobes pointing straight up? I had read an article a few days ago that had this, but I have been unable to find it again.

 

I assume that TDC is when the "0" on the tag aligns with the single tiny notch on the pulley. #1 and #4 both appear to be at about the top of the stroke.

 

What size is the crank nut. I have been using a medium sized crescent wrench?

 

What do you think of (pricey) ZDDP Mobil 1 Racing for non-cat cars? 

[Doctor510]

Crank nut id 1 1/16", to adjust the valves, do all the exhausts one at a time, then do the intakes, you'll always be right on.

Tech tip:  when adjusting valves, lift all the rocker springs out of its groove towards the center of the rocker, adjust the valve and put the spring back into its groove, that way you'll know that you adjusted the valve.  .008" Intake/.010" exhaust COLD!!!

 

Good luck!

[datzenmike]

Set the engine to TDC on compression stroke on #1. In this position, #1 valves are both closed, #2 the exhaust is closed, #3 the intake is closed and #4 both valves are open. These rockers can now be removed.

 

Rotate engine ONE turn to TDC again (this is now the exhaust stroke) Both #1 valves are open, #2 intake is closed, #3 exhaust is closed and both #4 valves are closed. These rockers can now be removed.

 

 

This method only requires you to turn the engine once to get all 8 rockers out..... or to set the timing. If setting the timing, this method is the fastest, and you can easily adjust all eight before they cool off too much.

[610StaWag]

Good News! You were 100% correct Datzenmike. I did the rocker removal, and used a small sledge to hit a short fat hardwood dowel to knock the valve down/open. After that I replaced the rockers and did a compression test all the cylinders: #1= 150, #2)=155, #3=150 and #4)=155. The number 2 and for were the bad ones. Now they are the best. Guess I might as well tap on the #1 and #3 now. 

 

I have read that I should set the valves, Int @ .008 and Ex @ .010, but I have also read other folks that have said to go .009 for the intake and .012 for exhaust. I am not looking for high performance, just dependable and economical performance.

 

Now I need to take the carb to a shop to see what plugged it up. I got a new fuel pump, but the carb body doesn't fill with gas, even when I use a make-shift gas IV bottle (with vacuum relief) to by-pass the fuel pump. This IV gas drip did work for me on this 610 a few years ago. The 610 Datsun has not been actively driven for well over ten years.

 

Now that it looks like the car is going to live, my wife asked, "Are you going to fix the air conditioning?"  So, all Datsun folks out there, do I just need to get a modern small compressor from a car in a wrecking yard? Does anyone have any suggestions?

[datzenmike]

There are two settings for the valve clearance. 0.008" and 0.010" for intakes and exhaust are cold settings. This assumes that when everything warms up the proper clearances will happen. I would use the cold setting if putting a cam and valve train together for the first time. It's close enough. A far more accurate method is to warm the engine completely, maybe 20 minutes, and make sure the temp gauge is up at the normal operating range, roughly half way up on the NORMAL range. If your engine does not warm up properly the thermostat may be old and stuck part open.

 

 

 

Turn the engine until TDC on the timing scale pointer. This will allow half the valves to be closed and the rockers easy to pry out. Turn the engine ONE complete turn and bring to TDC and you can remove the other 4 rockers. As mentioned only the arms that don't have a cam lobe pushing down on them can be removed. Do not pry on the cam lobes, only the spaces between.

 

 

 

Use this method to set all the closed valves. At TDC compression on #1 set the lash on

 

#1 int.

#1 ex.

#2 int.

#3 ex.  Turn ONE turn and set

 

#2 ex.

#3 int.

#4 int.

#4 ex. Using this method you should easily be able to get them all done before the engine cools off.

[Dirttrack510]

As usual, Datsunmike saves the day :thumbup: