740 cam chain and timing
 

I bought a 740 saloon with a B230E replacement engine which was destined for the scrap yard. It has a multitude of minor problems, and I've fixed a few of them, and I'm really enjoying driving the car. There is a ticking noise from the engine, and I read somewhere that sometimes this can be cured by advancing the ignition. Today I tried an experiment. On checking the distributor, I noticed that the timing mark on the distributor was below the mark on the cam cover, and I would guess it was about 2 degrees. I realigned these, and the engine sounded as rough as anything, so I moved it back and added what I would guess to be another degree. This seems to have made the car more responsive, so the first question is - have I advanced the engine by another degree? The improvement may be a bit subjective, as the Volvo feels like a McLaren after driving my 3.5 tonne LDV for a few years.

The next Q relates to the timing chain. The engine is of unknown vintage and mileage, but I believe it is older than the 1988 740. I understand that the timing chain may have stretched a bit, and at what stage should I consider replacing it? That is assuming that chains are still available. Is it an interference head, and I should play safe by replacing it?

It’s a belt bud, change as soon as possible if you don’t know when last done!👍

Thanks
I don't know where I got the idea it is a chain. I've looked at the belt cover enough times. I gather that a few engines ate interference to squeeze a bit of extra horsepower, so a change looks like a sensible precaution.
I'm still not sure about the ignition timing, and I may take the cover off to see if it is tappet rattle.

The interval is 5 years or 48k miles I believe

If the dizzy is mounted on the back of the head, the timing is non-adjustable but make sure the nylon hose from the inlet manifold through the bulkhead to the EZK ignition ECU above the brake pedal is intact and the manifold stub is clean internally - will make a world of difference if that's loose and/or blocked and you remedy it!

Have a look at the timing belt and find out whether you have square or round teeth on it. Square teeth are 36k miles/3 years, round teeth are 4 years or 40k miles if memory serves - if in doubt err on the side of caution and renew at 36k miles but for the cost of a new belt, do it ASAP and you know it's been done - don't forget to retension it after 600 miles too!

Some distributors have two holes so they can't be adjusted and others have a slot one side so you can adjust them, they usually have a molded plastic insert in the slot that only allows you to bolt it in one position. However we all now what happens to heat cycled oil soaked plastic and it sounds like it has broken up and gone wandering on this one so it can be adjusted.

I'll double check my manuals for the belt interval as I don't ever remember seeing a different change interval for the different teeth. I know the Haynes manual just says 5 years or 48k miles.

They are both 5 years or 50k for belts regardless of square or round teeth

Checked my Haynes as the green books didn't say an interval, I was in two minds between 48 & 50k and the Haynes says 50k :)

Just checked my Haynes book for the 760 and that says 4 years/48k miles. For some reason the Volvo 7/9xx Data Pocket page has disappeared from the wibbly-wobbly-web as i'm sure that is where i saw the 36k and 48k intervals as i quoted above. Fairly certain an older 740 Haynes book quoted 36k miles on the square toothed belt and that tallies again with what i quoted above.

If memory serves the B230E is non-interference so won't be a major problem if it does fail, just inconvenient although prevention is always better than cure.

That's where I got 48k from then as I've got a 700 Haynes too.