Timing Chain Noise

[david.g.chapman]

My timing chain makes a slight rattle up to 1500rpm, and only when the engine is hot. I can't hear much at higher speeds.

I have just replaced the timing chain tensioner spring with a standard new one from Burton Power (it seemed to be as springy as the old one).

The timing chain adjuster is set for 0.5 inch of play in the chain. The chain is new, and the slipper pad is virtually new as well. I tried moving the tensioner sprocket with a screwdriver, but it seems pretty solid. That spring does not seem to be doing much.

Should the chain be silent when the engine is hot, or is a little rattle the norm?

Some years ago Keith Franck had the same problem, and solved it with a stronger spring. Does any one know of a source in the UK?

Dave Chapman.

[bcmc33]

Why not try a longer spring designed for the tall block long chain. This is sold by Burton and QED.

However, it does seem to be treating the symptom and not the root cause.

[frearther]

During my last rebuild, I found that the bore in the front cover (the one that the plunger rides in) was rough enough that the plunger did not move freely over the last fraction of an inch of travel. That meant that, no matter what I did with the spring, the plunger could not exert enough pressure on the tensioner to remove the slack. A little careful polishing took care of it.

[david.g.chapman]

Thanks to both of you.

I took the cam cover off again and had another look. If I slackened off the adjustment by several turns I could move the tensioner sprocket away from the chain with a long screwdriver, and it sprang back satisfactorily. However, I am not so sure when the adjuster is about 3/4 of a turn from the coil bound position, which corresponds to about 1/2 inch of free play.

I did find that the 1.2 inch measurement takes a bit of experience for me to get "right". You can set the adjuster so that if you just apply light force to the chain the deflection is 1/2 inch. As the adjuster is wound in further the defection still seems to be 1/2 inch, but more force is required to deflect the chain. I carried on until the point where I started to lose the 1/2 inch deflection. I could not see the adjuster sprocket moving, though - maybe the movement is too small to notice.

I have not run the engine hot yet, but will do so in the next few days. If I still get the rattle I will look at the possibility of the plunger sticking. I have never had the chain make a whining noise, so perhaps I have never had it too tight (or tight enough) and I have got it right this time.

Update for 4th April - I have taken the car for a run with the engine hot, and there is no rattle.

Dave Chapman

[billwill]

Have you looked into the possibility that, when tensioned, the chain is touching the inside of the timing case near the water pump. This is more likely (I think) if you have converted to a chaincase with podule water-pump.

Mine was doing this and so I fitted a new timing chain, which was a smigeon smaller due to lack of wear. The clearance between the chain and case is very small though.

The possibility of this happening is increased if the head is skimmed because this brings the camshafts closer to the crankshaft sprocket. i.e implying a shorter chain.

I was wondering whether I was going to need to find a special 119 link or 118 link chain instead of the standard 120 link, but it looked as if 120link chain is just about OK, though not much allowance for future wear.

Somewhat academic now until I get a new head.

[david.g.chapman]

Sorry to hear about your head Bill.

I had a look at the chain fouling the water pump casing on the front cover, and there is clearance there (I do have a Burton replaceable water pump module though).

The chain also just misses the join between the head and the block.

I suppose the clincher is the twin marks of the chain on the inside of the cam cover - although I don't know how old they are.

I did a sneaky edit on my previous post. There is now no rattle from the chain. I did have to keep increasing the tension untill I was just about to lose the 1/2 inch even with a hefty pull and push. At that point the chain felt springy - maybe that was the tensioner working!

Dave.

[frearther]

The "hefty push" for the 1/2" clearance is what works for me, too.