Timing chain too loose

[Jimmer84]

I cant seem to get my timing chain to get tight enough. I have it on the #3 hole, and the mark is still to the left of the notch. I have replaced the guides,tensioner and chain. I added more cam tower spacers, and it got better, but when I start it, it still rattles at low RPM. This is a former road racing motor, and it was machined at some time. I dont know how much. How thick of shims can you put under the cams? Are there different chains for different years? Do I have to replace the gears as well? This thing is driving me insane!

Thanks
Jim

[datzenmike]

Properly timed the etched mark on the cam thrust plate SHOULD be just to the left of the cam sprocket VEE.

[img]http://i138.photobucket.com/albums ... .jpg[/img]


If you have the motor precisely on TDC and cannot get the VEE on or slightly to the left of the etch mark, the only thing to do is replace with a new chain.

[Jimmer84]

I already replaced the chain, tensioner and guides.

[datzenmike]

.... and the mark is still to the left of the notch.
Thanks
Jim

Properly timed the etched mark on the cam thrust plate SHOULD be just to the left of the cam sprocket VEE.

[img]http://i138.photobucket.com/albums ... .jpg[/img]


If you have the motor precisely on TDC and cannot get the VEE on or slightly to the left of the etch mark, the only thing to do is replace with a new chain.

[510Freak]

Is the spring in the tensioner?

[datzenmike]

Hey lou!

The tensioner only 'tensions' the slack side of the chain and has no effect on the tight side or cam timing.

[510Freak]

Hi Mike,
Just going by what has been said, rattles a bit at low rpm .

[datzenmike]

Right.

[Jimmer84]

yes the spring is still in the tensioner. but like was said, that should have nothing to do with the tight-side of the chain. how many shims can you stick under the cams? is there a difference in timing chains year to year?

[slodat]

The L20b timing chain is longer than the L16/L18 chain..

[datzenmike]

By about 4cm.

When you installed the slack side guide did you push it as far over to the right against the chain as you could?

[Jimmer84]

how much longer is it?

[datzenmike]

If you have a new chain and tensioner with guides it should work. However if the head has been milled then this will introduce some chain slack. Cam tower shims should raise the cam sprocket and correct it. The tensioner should easily handle and slight slack.

The tensioner itself is supplied with oil pressure from behind which adds to the spring pressure. Oil pressure is lower at idle so this may account for the rattle. This is the back of the tensioner showing the oil inlet hole from the block. The oil bleeds out past the spring and lubes the chain, though I don't think that's it's main purpose.

[img]http://i138.photobucket.com/albums ... .jpg[/img]

IF THIS is the cause, the best way to increase idle oil pressure is to install a Hi Vol oil pump from an '88 and up 240sx KA24E motor (not the DE motor) or a Z24i, KA24E AND DE motor from an '86'5 and up D21 Hardbody. I put one on my tired old L20B and the hot idle oil pressure went from 17 lbs to 29 lbs. With no other change. Operating pressure remains the same, there is just more volume available. If this does not fix the problem the money is well spent on a far better oil pump for your motoranyway.

[Jimmer84]

If you have a new chain and tensioner with guides it should work. However if the head has been milled then this will introduce some chain slack. Cam tower shims should raise the cam sprocket and correct it. The tensioner should easily handle and slight slack.

how many shims can you put on it? can you put too many shims in?

[datzenmike]

I only know that shimming changes your rocker arm contact area and the lash pads have to be changed to retain that same contact point.