Timing chain tension sprocket

[gordon]

My 230 65 sl engine has been rebuilt by me in stages over the last 4 years and I'm now intending to finish it this time. Amongst other things it's had a new timing chain and I'm about to fit the chain tensioner. The tensioner sprocket is in place and the chain is very tight to the extent that the lever ( against which the tensioner acts) on the sprocket is tight against the inside of the head with no space to poke a screw driver into a gap. The engine rotates without problems with all the marks lining up.
 I can't see how I can bleed the chain tensioner if the lever of the sprocket is hard against the inside of the head. Also I wouldn't have expected that chain to be so tight.

All comments will be gratefully received

[stickandrudderman]

You're right to be cautious; it should not be tight so something is wrong.

[MarkCan]

Why not just remove the whole thing. This is also a great opportunity to clean the unit and remove the sludge accumulated over the years. Remember the oil goes in there and stays in there. It’s not all that complicated, 20 min and you are done.

[MarkCan]

Here is the pic,
Remember to fill the cylinder with some oil when assembling.

[gordon]

Thanks guys. I need to get to the bottom of the tight chain.
I'm sure I compared the new chain to the old when I did it and they were same length. Where could I have lost the equivalent of a link or two of chain length?

[gordon]

MarkCan , what do you suggest in a 20 minute strip down to determine where the difficulty lies?

Thanks Gordon

[MarkCan]

MarkCan , what do you suggest in a 20 minute strip down to determine where the difficulty lies?

Thanks Gordon

I don’t suspect any problems. It is tensioners job to hold the chain tight. Imagine what would happen if the tensioner backed out with the engine is off.
Loosen the big nut on the front, than take the whole assembly out. Take it apart, clean it, fill with oil and put it back.

[gordon]

My concern is not about the tensioner which is out at the moment, it's the fact that the chain is so tight with the tensioner not fitted and it's not possible to rock the tensioner sprocket arm which should be possible for the tensioner to work.

I think it's back to basics time.

[MarkCan]

That is really odd. Why don’t you take the distributor cover off. That will give you a nice inspection window. It is possible to place the sprocket out of alignment.
If by any chance the bolts on the crank or camshaft were secured/torqued without locking the shaft first that could make the chain jump. But you already told us that all the marks are lined up.
What I would do here? I would pull the rockers off. Get the chain out and measure it. Don’t worry you can put it back in no problem.
I have my old chain that I’ll measure for you in a bit.
Most important, make notes of whatever you do.

[MarkCan]

Here you go;
1271mm + the master link (10mm)

[gordon]

Hi Mark, thanks for your input. I've just measured the old chain which is the same length as yours. I've removed the rocker arms with the idea of feeding the old chain in, but before I do that
I'll remove the distributor and cover as you suggest and hopefully see what's going on.

[gordon]

Ok, I think I've found the problem. Removed distributor cover all looked ok, dropped the sump and think I can see loose chain on the bottom of the crank sprocket, probably 1 link. I think that as the chain rotates the situation remains unchanged. Because of the chain guides it's not possible to dislodge the surplus chain towards the tensioner or in the other direction so I think I'll need to pull the chain and start again .

I'm ok with lining up the crank, cam and distributer but unsure about disturbing the injection pump timing. Should I pull the distributor drive sprocket them replace it.

More guidance would be appreciated, Thanks, Gordon

[gordon]

Hi all, problem solved, the chain was not engaged on one tooth on the crank pulley at the bottom. This resulted in the chain being loose at the bottom of the crank sprocket but fully engaged at the sides of the sprocket, hence every thing rotated. How I managed this I don't know.
Timing is reset wth the exception of the injection pump which I'll remove and reset.

Thanks for all input, received with thanks.