when to replace timing chain?

[nathan_454]

First off searched and didnt fint what i was looking for.

 

When should the timing chain be replaced on an l20b. I have a new to me '80 720 pickup with 140K on the odometer. It runs nice and smooth with no noise .but i want it to last. and wondered if theres any way to "check" the chain? I know better safe then sorry, might as well replace it. but want to know if i should or not.

[nismo dr]

there is no rec. interval, if its quiet and your timing is right, leave it alone

[I'm BLUE]

there is no rec. interval, if its quiet and your timing is right, leave it alone

 

that reminds me , mine has a rattle ( at idle sounds like guides are gone but IDK for sure , going to slap new set in and not screw with it ) :lol: ........... better change before I lose it :unsure: :o

[datzenmike]

There's a procedure for checking chain stretch and adjusting.

[nathan_454]

ok great....anyone know what it is? that is willing to share?

 

 

There's a procedure for checking chain stretch and adjusting.

[nathan_454]

edit...found it.

[datzenmike]

The sprockets and chain can wear or maybe stretch and this will effectively advance the cam which in turn will slightly enhance top end but ruin bottom power and torque. Nissan provided a way to retard the cams by 4 degrees too offset this.

 

I'll finish to-morrow, I tired and it was hot and humid at work. Gotta go lay doooon. :mellow:

[nathan_454]

thanks datzenmike, I found your writeup in the other section. I will check mine tomorrow. I am a diesel mechanic by trade. and to be honest anything without timing gears spooks me... too many variables. lol thanks again!

[nismo dr]

if its not broke - fix it till it is

[banzai510(hainz)]

watch this

http://www.guba.com/watch/3000024223/Hainz-Datsun-L-Series-Engine-01-Timing-Tare-down-and-Rebuild

[nathan_454]

A few questions.

 

1. does the OEM Timing gear have 6 holes in the cam gear or 4? mine has 6? maybe it has been replaced already.

 

2. is it OK if the tight side guide is touching on the case, not tight against the chain?

 

3. I assume i am fine because the v-groove is lined up with the dash? i made sure and turned it so the tight side of the chain was tight.

 

here are some pics

 

 

 

Uploaded with ImageShack.us

Uploaded with ImageShack.us

[datzenmike]

1/ Number of holes don't matter. The cam dowel will always line up the hole anyway for checking the timing.

 

2/ Hainz would know, but I think the plastic guide material is beveled at the top so it looks like the chain isn't against it, but further down it is.

 

3/ L20B are usually set on the #2 setting from the factory.

 

[nathan_454]

so is mine messed up because its on number 1 instead of number two?

[metalmonkey47]

if its not broke - fix it till it is

 

 

 

 

 

It ain't broke till you can't fix it anymore.

[datzenmike]

No, the setting look s fine and that governs. If it looks right.... it is. Just be sure you are precisely at TDC while turning clockwise.... and it is what it is.

 

L16/18 are on #1 but L20Bs are on #2. Hainz says it's for emissions or something.

[zed]

The service schedule in the owners hand book which came with my Nissan Hardbody - which has the L18 motor - says the timing chain should be replaced at 100 000 km. But before I learned to work on my Nissan I took it to a big city Nissan dealer here for services: the workshop foreman said they don't replace the timing chain "unless it's noisy"...

[banzai510(hainz)]

Looks good/perfect.

dont worry about it.

 

olddatsuns.com save it as a link. lot of good tech info

[Donki]

My 80 Datsun 720 l20b chain is on number 1 it has 110 thou on it I thought if chain is stretched u move it to 2 

[datzenmike]

All L20B come from the factory on the #2 cam position.

 

 There is provision for moving the sprocket to the #3 hole if it's found the chain has stretched, (I have never seen this) or the head has been milled. To check if the cam is properly timed do the following....

 

Set the engine to TDC on the compression stroke of the #1 cylinder, accurately. Use the notch on the crankshaft pulley and the timing scale just behind it near the alternator. Turn the engine with the crankshaft bolt and a ratchet or breaker bar. It's vitally important that the notch and the 0 are lined up by turning in a clockwise direction and stop. Do NOT back up any amount to set this. If you over shoot the mark then back up 1/4 turn and try again. If it takes 7 tries then this is what it takes so don't expect to get it on the first try. Turning only clockwise assures that all chain slack is on the right side of the chain (left as viewed from the front) and the cam ready to examine.

 

Take the valve cover off and look through the top hole in the cam sprocket and down behind it. If the cam is timed properly and the chain not stretched you should see this...

 

This cam is properly timed. L16/18s were factory set on the #1 hole.

 

Note that there is a U or a V notch on the back of the sprocket and just behind it a small horizontal etched mark on the cam thrust plate. If the cam is properly timed the V notch will be under or just slightly to the right if the small line above it. If the chain in worn or the head was milled you may find the V notch way over to the left and the cam will be too advanced. A too advanced cam will have poorer low end torque that it should have.

 

DO NOT remove the cam sprocket and try to move to the #2 or #3 hole without first finding out how to properly secure the timing chain tensioner. Failure to secure it before removal will allow the tensioner to fall out. This will mean the front of the engine must be taken apart to retrieve it. Add 6 hours of frustration to your job.

 

For now lets just examine if your cam is in need of adjustment or not.