1975 620 Longbed "Shelley"

[Jskinny]

5 minutes ago, datzenmike said:

Rocker may have come off.

Lock nut on adjuster may have loosened

 

I had the valve cover off yesterday and didn't notice anything visually. If a rocker came off wouldn't that at least cause a misfire? 

 

Unless you mean just loose, in which case you'd have to turn the engine over until each cam lobe is not engaging its rocker and see if the rocker moves?

 

Again I'm just learning as I go.

 

 

[datzenmike]

Rockers have been known to jump off the pivot post if clearance is excessive and revved too high. If an intake the cylinder won't fire, if an exhaust it might pop back through the carburetor.

 

To quickly check/set the valve lash, warm the engine and set the engine to TDC compression stroke on #1 cylinder. Check that the first cam lobe is at 2 o'clock and the second lobe is at 10 o'clock as viewed from the front.

 

Now adjust both valves on cylinder #1, the intake on#2, the exhaust on #3

 

Turn engine ONE complete turn...

 

Adjust the exhaust on #2, the intake on #3 and both valves on #4.

 

This avoids tediously bumping the engine around with the starter (and over shooting) and is fast enough to do before the engine cools down. This is a HOT clearance setting so 0.010" intake and 0.012" exhaust.

[Jskinny]

21 minutes ago, datzenmike said:

Rockers have been known to jump off the pivot post if clearance is excessive and revved too high. If an intake the cylinder won't fire, if an exhaust it might pop back through the carburetor.

 

To quickly check/set the valve lash, warm the engine and set the engine to TDC compression stroke on #1 cylinder. Check that the first cam lobe is at 2 o'clock and the second lobe is at 10 o'clock as viewed from the front.

 

Now adjust both valves on cylinder #1, the intake on#2, the exhaust on #3

 

Turn engine ONE complete turn...

 

Adjust the exhaust on #2, the intake on #3 and both valves on #4.

 

This avoids tediously bumping the engine around with the starter (and over shooting) and is fast enough to do before the engine cools down. This is a HOT clearance setting so 0.010" intake and 0.012" exhaust.

I checked yesterday on cylinder 4 (frontmost cylinder) and both valves after being warmed up were too tight using the .010 and .012 feelers, respectively. 

 

I had the 2 cam lobes on cylinder 4 at 10 and 2, but I think the notch on the timing chain gear showed a 2... I'll have to double check.

 

Either way, didn't get too far but I'm planning to continue tonight and see if I can get anywhere.

 

I appreciate the step by step!

 

[datzenmike]

The front most cylinder with the distributor on the left and the fuel pump on the right is cylinder number one.  Having it the opposite way round could cause enormous problems in understanding when trying to explain a problem to someone else.

 

 Plus or minus a thousandths of an inch or two is fine. The 0.010 and 0.012 clearance is considered the proper setting on a warm engine and provides enough valve on seat time to transfer heat to the seat to keep the valve cool enough. When the clearance gets tighter the valve runs hotter.

[Jskinny]

25 minutes ago, datzenmike said:

The front most cylinder with the distributor on the left and the fuel pump on the right is cylinder number one. 

 

Hmm the cylinders must be mislabeled then from the previous owner... seems to run smooth so maybe things are matched up correctly but just mislabeled. .

 

Currently I have it as cylinder 4 closest to the grille, and cylinder 1 closest to the firewall. 

 

<blockquote class="imgur-embed-pub" lang="en" data-id="a/oyzKhMs" data-context="false" ><a href="//imgur.com/a/oyzKhMs"></a></blockquote><script async src="//s.imgur.com/min/embed.js" charset="utf-8"></script>

 

If that doesn't embed properly I'll try to upload it when I get off work, I'm on mobile right now. 

 

https://imgur.com/a/oyzKhMs

Edited October 4, 2023 by Jskinny
Maybe the link will work

[datzenmike]

If the plug wires, they're just miss labeled. As long as you know which is which and it agrees with everyone else.

[Jskinny]

Got the valves adjusted tonight. Seems to be running a bit nicer, at least a bit quieter.

 

However it just made the noise coming from the timing chain end more apparent.

 

With all the chain slack on the driver's side of the engine, it seems like there is a more slack than there should be... It slaps around pretty good as in these 2 clips. (probably not set to TDC on any of the cylinders if that matters, but this was after we finished with the valves.)

 

We noticed there seems to be some marks along the level where that bolt is... there's no way the chain would move that far side to side, so it has to be just where they ground down the casting from the factory, correct?

 

However there were some wear marks from the timing chain on the inside of the valve cover (which i neglected to get a photo of) Would this point to a tensioner issue like Stoffregen mentioned, or could this be a stretched chain? Something else?

14 hours ago, Stoffregen Motorsports said:

If this noise just started, it could be that the rubber face of the chain tensioner ground or broke off, and the chain is not riding on metal. This is common with old tensioners (and guides) as the hot oil hardens the rubber over time making it brittle.

 

 

Seems like the only way to check the tensioner is to remove the radiator and shroud... which seems like loads of fun. 

 

Edited October 5, 2023 by Jskinny

[banzai510(hainz)]

Stop!!!!!!! seeing the socket on the cam sprocket is wrong already!!!!!!!!

you tighten the driver side of chain by turning the motor clock clock wise from the CRANK bolt then there will never be slack on driver side.

if anything the slack side guide needs to be adjusted and or new  with NEW tensioner.

 

dial the motor to TDC coming up to zero on crank then look where your V and dash on the sprocket is. then youll know if you have chain stretch , but most likely the tensioer is wearing or or guide wasnt perfect either.

see how much slack you go on the pass side slack side guide.stretch after you dial to zero.

 

think your fine running it as is unless you think someothing otherwise I dont know about.

if starts goes up hills fine its timed mechanically and electrically(disributor wise) I wouldnt worry about it

 

tensioner ?you can look down passenger side and see how far out it is .  I had mine that was out and cocked 45 deg wearing down to the metal. But still ran.

Edited October 5, 2023 by banzai510(hainz)

[datzenmike]

The engine turns clockwise and pulls down against the resistance of the cam and opening valves. It is always tight on the distributor side when running. 

 

I don't see how the chain would stretch, it's quite robust, but the sprockets and rollers might. If there is any 'stretch' the valve events happen later and later in relation to the crankshaft position. The intake valve would close later on the compression stroke and at low speeds wouldn't allow full cylinder filling but at high RPMs would. 

 

Check your chain 'stretch' by turning crankshaft up to and stopping at exactly TDC on the compression stroke. If you back up it will move slack to the normally tight side and ruin this test. If you over shoot TDC back up at least 1/4 turn and keep trying. Only in the clockwise direction will keep the slack on the aptly named 'slack side'.

 

Once set, take the valve cover off and look through the top hole in the cam sprocket. On the back of the sprocket is a Vee notch and just above it on the cam thrust plate is a small horizontal etched line. If the notch is to the left of the line above it there is 'stretch' and this can be adjusted out by repositioning the cam sprocket. What you want to see is this, with the notch just under and slightly left of the line...

 

 

Do NOT EVER try to remove the cam sprocket without knowing how to secure the tensioner from falling out!!! Very important.

[Jskinny]

Ok here's a newbie question- 

Is TDC achieved just by looking at the notch behind the cam sprocket, and making sure its slightly to the right of the horizontal line? 

Does it matter which number is at the top? (in the example it's 1) I read somewhere that for the L20b it should be the 2?

 

 

We were getting a bit confused since we couldnt find the harmonic balancer.. my friend is used to chevy small blocks.

 

I'm new to timing stuff so forgive my ignorance.

 

I'm mostly worried about the chain wearing down something and then getting sparkly oil.

[datzenmike]

TDC is set by the notch on the rearmost part of the pulley on the crankshaft aligning with the 0 on the timing scale. There are 2 TDCs on a four stroke engine. You want the compression stroke on the #1 cylinder. If not sure take the valve cover off and both valves should be closed. If not you are on the exhaust stroke so turn engine ONE full turn.

 

 

[iceman510]

On 10/5/2023 at 12:36 AM, Jskinny said:

We noticed there seems to be some marks along the level where that bolt is... there's no way the chain would move that far side to side, so it has to be just where they ground down the casting from the factory, correct?

 

 

 

 

Yes, that is correct.  Those marks are not from the chain.

[datzenmike]

It's where the casting flash was ground away at the foundry. The 'bolt' is just a sealed hole used for removing the internal casting sand.

[banzai510(hainz)]

your motor is fine.

 

[Jskinny]

So.... I figured out what the unpleasant noise was... I was driving around a roundabout and the oil light flashed on and off for a second or two. Pulled off for a bit, and added some oil. Started it up and the sound went away within a few seconds. So I guess I've learned what low oil sounds like.

Typically its hard to get a reading on the dipstick.

 

I haven't noticed any leaks, so I guess its just burning a bit of oil. Hopefully that doesn't point to anything bad, haven't noticed much smoke apart from starting it up on cold mornings for a few seconds.

 

Got behind the orange 510 we have in town. Hopefully I didn't embarass him too much with my holey exhaust...

 

Also stopped at Deception Pass with my fiance - as we were leaving I had a gentleman come up and compliment my truck, said he had one as his first car in the early 70s when they first came out. And as he left there was another guy across the road with a nice-looking camera taking photos of us as we left.

[hobospyder]

orange 510 would be @sturdys.speed.shop on instagram, don't remember his ratsun name but he also has a drift 620 now. good kid

[hobospyder]

mentioning the drift 620 was my way of saying i'm sure he wasn't embarrassed. probably enjoyed it

[Jskinny]

Haha his sounded miles better than mine. Might start looking into exhaust next...

 

Where's a good place to start for figuring out an exhaust for an L20B? I've seen a few threads with various setups, but I tend to get lost when people start talking back pressure, pipe diameter etc. I've heard you shouldn't go any bigger than 2" or 2.25"?

I like the idea of something period correct, but a proven combo that sounds good would also be good. Just don't want it to sound like a fart can. 

 

I also want to install one or more 12v cigarette lighter/accessory outlets.  I've seen some 620s have them from the factory, but mine has the choke where most have the cigarette lighter. 

Is there a specific circuit I should tap into? Or something that would have been a placeholder? 

 

Been reading through some more build threads, making me want to keep working on my own truck! 

 

I put some door pulls on. They look nicer than the old grimy door handles, but I'm not sure I like having to reach farther and not have an arm rest....

[banzai510(hainz)]

If your oil light comes ON when you go around the corner means you been LOW for a long time.How much wear you put on the motor.Bet your a oil burner from now on.. Someone told me it only takes 5 pounds to make that light go out

5 quarts is about right. I put 4.5 in then run it with the new oil filter then add per the dipstick to get it right.

 

 

2inch is fine for a exhaust and mufflers plentiful aluminized pipe, it will last for 20plus years

I myself being older would run a quiet muffler like a walker turbo type case. Trucks I just like less noise now.

I have a super turbo from Dynomax  very small case. Its quiet once warmed up. But wakes the neiboors in morning. They know what time it is.

Edited November 9, 2023 by banzai510(hainz)

[Jskinny]

Been trying to figure out gauge bezel removal and need some help. The 3 screws in the top of each gauge bucket were easy, but the radio seems to be what's keeping the entire right side attached to the rest of the dash? 

 

Can't see any fasteners apart from the two nuts which look like theyre a part of the heater/air controls, and those are part of the entire bracket.

 

I was watching this video and he says the wash/wipe knob is what holds the rest of it in but it feels like there is something else back there holding mine in. Would the radio knobs be causing this?

 

 

 

Going to check back on this in a few days, we got a random dump of snow so now everything is cold.

 

This dude was watching me today...

[datzenmike]

Take the wiper knob and the two  heater control knobs off and the bezel should just slide off towards you. Remove any knobs on the radio.

 

Pull the wiper switch all the way out. Grip the stem tightly with needle nose pliers and hold. Push in on the knob and twist to release.

The heater knobs just pull off or have a screw on the under side

[Jskinny]

wipe/wash knob came off easy. There was another screw into the bezel on the left of the radio deck, I think there might be one more I need to find. Here's the screw location conveniently pointed out.

 

 

Knobs just pulled off like was mentioned. There is a nut and washer on each of the radio tuner pins which come off before the radio comes loose.

 

So now i think there is one more screw to the right of the radio? I'll have to check again. Then is the heater controls and hopefully the whole thing will come out.

[hobospyder]

That screw you removed was for the foam pad not the bezel. You can come over and look at a loose dashboard if you want, I just don't have a radio or radio bezel in it

[hobospyder]

From me looking at the loose one you should have everything loose if you got the 3 screws in the gauge holes, wiper switch, lighter, radio and climate controls

[datzenmike]

I always forgot the cigar lighter. What about the heater and radio knobs?