Timing belt or chain-which is best?

What vehicle is fitted with a duplex timing chain but no tensioner?

The message from "Mike G" contains these words:

Better yet, take the fan off and fit an electric one. It'll rarely come on unless stuck in traffic.

My old mini for a start.

Presumably it would have to be fitted in front of the radiator, as there's very little space between the w/pump and radiator. There's only enough clearance for a Viva fan, if one takes into account engine movement under heavy braking. Mike.

The message from "Mike G" contains these words:

Nowt wrong with that - it's how the Maestro/Montego did it.

Reverse mounted fans are fine. 306's have them and so does the Corsa valver I knocked together.

It was only an observation, not a criticism. Both my BMW E39 and E34 have fans in front of the radiator, so it must be a good idea from an engineering POV. :-) Mike.

Minis all have tensioners.

Only aux fans, though. The viscous coupled one does the main work.

The message from "Dave Plowman (News)" contains these words:

Yebbut - they only work for a thousand miles or so before they start to rattle again.

Where?

Chris

"bucket" wrote in news: snipped-for-privacy@corp.supernews.com:

I must add that I did this with two other very cosseted Volvos and a "home-maker" wife who could pick me up in a trice after a quick call on the mobly. Which happened once when the hose from the radiator to the head split down its length and dumped all the water when I was WOT leaving the toll booths on the FRB. I kept it WOT until I crested the bridge then switched off and coasted to the lay-bye on the north side. A quick visit to my garage for a length of hose and a couple of 1 gallon water carriers I use for camping fixed it. That was at about 250,000 miles.

The message from Chris Whelan contains these words:

It's a slipper sort - in effect a rubber block with a leaf-spring which almost, but not entirely, manages to fail to stop the chain rattling.

Or even before you drive out of the garage. ;-) But it's part of a Mini's charm.

On the earliest ones, two rubber rings round the cam cog. Not that they do much for long.

I've just dug out the manual I have for pre '72 Minis and there is no mention or picture of them. Likewise for the Cooper/Cooper S. I'm sure they were not fitted to early cars, although it was a long time ago since I had one in bits!

I rallied a Cooper S in the mid '70's. One of the (many!) mods I did was to fit the BL Special Tuning uprated timing chain kit, which was basically just the duplex bits from something else. I remember being amused by the novelty of the O-ring "tensioners" because I ran a straight-cut gearbox, straight-cut primary gears, and a Weber 45DCOE which ended up roughly where the speedo should have been. The last thing I would have heard was the timing chain!

I'm absolutely certain that the single chain and sprockets I removed had neither O-rings, or the grooves for them.

Chris

*All* the early A Series I've ever had apart had them, IIRC. It might not have been obvious as old ones look very much like part of the cog. The first Mini I had was early - it had the non baulk ring gearbox.

The only BMC workshop manual I have to hand is for the Midget, and that clearly shows the rubber rings and simplex chain for the 948 version. It would be easy to send you a scan of that page if you'd like.

Mine was a '66 with of course the single row chain from the factory but as I mentioned in my post a *modification* is to fit a duplex chain and gears for which I'm pretty sure there was no tensioner fitted. Probably is described in the "tuning the A series engine" book.

So not all minis have tensioners 'cos mine doesn't. ...or at least it didn't - I sold it a number of years ago.

Ignoring side valve and OHV pushrod motors. other than racing engines it's not been seen on OHC cars for years and it was very rare even then.

70's Nissan LZ race engines used gear train to a short chain. Honda had to use gears when failure of Hi-Vo inverted tooth chains in the VFR750 V4 showed that they don't have a clue about designing cam drives for 180 degree twins. Exactly the same root cause lies behind the K4, G5, CJ and CX500 problems. They did manage to cure the CX500 by fitting a bigger bolt. K4's snapped the camshaft so on the G5/CJ they fitted a middle bearing, the tensioner snapped on those. On the Superdream twin they used a hi-vo chain and thought they had fixed the problem but that was a 360 degree twin and the problem doesn't exist. Exactly the same problem is inherent in the design of the flat 4 Gold Wing and V4 Pan European, they don't suffer failures as they have belt cam drive which can cope with the shock loads much better than a chain.

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