7 replies to this topic

[cian]

Has anyone any experience with belt drives or full sprocket timing set ups? Are they really worthwhile over the regular duplex set ups?

[Dan]

  In short, no they aren't worth the hassle IMO.  The belt drives used are of course very short and so get far more wear than a longer belt would, they need to be inspected and replaced very frequently (inspect at 10,000 replace at 20,000 miles) which is a pain of a job in a side rad car.  Belts aren't as efficient as people seem to think and while quiet they do absorb a lot of energy and heat up, which is all robbed from the engine so there is no real difference between a belt and chain in that respect.  Chains are more reliable and last longer.  The direct gear sets are very tricky to setup, and transmit all the harmonic vibrations and rattles in he crank directly into the valve train and timing whilst belt or chain drives dampen these vibrations out a lot.

[Ethel]

I don't think belts are that bad, the belt may be short, but it runs a less complex path, with less flexion, than other engine belts. It also avoids the need for a tensioner. It has less mass than a chain, which will help, and tinkering with the cam timing is much easier. I have to concede the cost/benefit equation isn't likely to stack up for most road cars, though.

[sledgehammer]

most new cars have gone back to chain - due to maintenance - or lack of it

[cian]

I ask the question as i am about to do a pretty comprehensive rebuild but is no " open cheque book" one of my items was a med duplex and the dsn billet timing cover, now both these items together are 310 quid so would i not be better getting a quality trick timing set up possibly saving a tenner or so lol

[Ethel]

I've seen a broken (simplex) chain; it eventually took the crank sprocket with it, with a fair bit of it ending up in the sump. I've never broken a belt, even after throwing a con rod through the block. Depending on your valve lift, neither a belt or chain failure should be terminal on an A Series.

 

Or you could spend a tenth of that and not be able to tell the difference from the driver's seat.

[Cooperman]

I've never seen of heard of a duplex chain breaking, even at mega-revs.

[mini13]

the cam lobes will usually take a nice chunk out of the rods on non S big bores.

 

 

 

I've seen a broken (simplex) chain; it eventually took the crank sprocket with it, with a fair bit of it ending up in the sump. I've never broken a belt, even after throwing a con rod through the block. Depending on your valve lift, neither a belt or chain failure should be terminal on an A Series.

 

Or you could spend a tenth of that and not be able to tell the difference from the driver's seat.