9 replies to this topic

[lordyoung1980]

Has anyone done it? Was it worth it? I will be rebuilding an automatic unit soon and wondered if it was a worthwhile mod. I will be mildly porting and modding the head to get a little more out of the engine and looking to reduce anything that could shorten the life of the oil and the timing chain and tensioner looks to be a good candidate to go. What's peoples thoughts?

[nicklouse]

An ISWS single chain and tensioner is more than suitable.

[mab01uk]

A single or duplex chain will out last a belt, which on a Mini will require more attention for inspection intervals, any oil contamination and replacement at a specified mileage or period of time.

Edited by mab01uk, 05 September 2026 - 10:40 AM.

[Ethel]

I've run a belt with no issues. It's theoretically more accurate, but with crank triggered ignition it makes no difference. It might be quieter, but I've not really noticed: it's still a tappety A Series.

 

Tinkering with cam timing is way easier, but I don't have a side mounted radiator or much in the way of inner wings. 

 

This seems over complicated & expensive, but it would do the above as well as one of the belt kits for about the same money once you've bought the sprockets to go in it.

[stuart bowes]

is this the video where he briefly mentions belts vs. chain.. maybe?  sorry don't have time to watch or find the bit again right now

 

but it's probably an interesting watch anyway

 

edit: youtube link not showing up for some reason.. ? 

 

if not working for you either I searched  "David Vizard - tuning the A-Series engine"

 

Edited by stuart bowes, 05 September 2026 - 12:18 PM.

[mab01uk]

is this the video where he briefly mentions belts vs. chain.. maybe?  sorry don't have time to watch or find the bit again right now

 

but it's probably an interesting watch anyway

 

edit: youtube link not showing up for some reason.. ? 

 

if not working for you either I searched  "David Vizard - tuning the A-Series engine"

 

 

Youtube links don't show up for me anymore either, just an empty space appears in the post, so I have stopped posting/sharing any recently.

I did ask why here...

 

You Tube Videos Not Showing In Posts?

https://www.theminif...owing-in-posts/

Edited by mab01uk, 05 September 2026 - 01:48 PM.

[Spider]

I did try them back in the 80's (and still have a couple), but went back to chain. Getting good belts, especially these days is a real mission and because they are such a short belt, they have a short life - the recommended change period for the Kevlar Belts was 12,000 miles / 20,000 km.

As mentioned, I still have a couple here, the dowel peg adjustable types. I'll fit these when playing around with cam timing as they are quick, easy and clean to adjust the timing, though, once I have landed where I want to be, and have a number, I'll then fit a chain.

[lordyoung1980]

Thanks for the feedback guys. Sounds like keeping the chain is the way to go. Off to Stanford hall next weekend so now I know what to add to my list.

[coopertaz]

also fitted a mini spares dowel belt kit back in the eighties the lower seal failed and soaked the belt down the M6 (luckily belt did not fail) understand they later changed the seal profile. Was definately quieter than even a new chain but this failure deterred me and been with twin chain ever since. Just been on their site and can see separate items but no housing or full kit listed!!

[bluedragon]

I'd like to emphasize that the quality of the chain, be it simplex or duplex, is key to making it a clear choice between timing chains or timing belts.

 

A high quality simplex chain like the IWIS chain is optimal because it is the simplest fitment and if you are counting angels dancing on pinheads, has the least frictional losses.

 

But the quality of the chain is vital. A cheap or lesser simplex chain will "stretch" rather quickly (actually it's chain elongation due to excess wear of the chain link points) which is why most enthusiasts went for duplex chains. Those extended the period before stretching affected timing, presumably due to halving the load on the links?

 

The belt did not stretch, maintaining timing through its lifespan. But going beyond the lifespan does have risks compared to a chain, since the belt could break or shed teeth whereas the chain is very unlikely to break or fail.

 

Chains of the quality of the IWIS are a fairly recent development by Mini standards (last 15 years or so) and I don't know what other chains, if any, are equal or superior to IWIS. So based on what I know now, if I were choosing today, it would be a simplex IWIS setup.