A question I often wondered the answer - why BMC moved to a duplex timing chain for the Cooper S, but Lotus stayed with the simplex chain…despite the Twin Cam having more grunt? Is more required to drive a single pushrod camshaft than a DOHC?
Not the main reason for the post though. I need a timing chain, Supplier is out of stock, and looking around, I see one from Mountune - extra HD etc etc made in Germany for tough use etc etc, but at $114 against £30 odd in Europe!
Questions therefore - other than on a concurrent thread, do timing chains break (I only see one reference on the internet - someone pushing too hard on the main straight of Catalunya…)? Will I benefit from one from Mountune? I assume that all chains supplied by the likes of Burton, Kelvendon etc are continuous link. or must I specify at order?
I’m sure burtonpower are with no split links.
If you follow saint Miles for sure no split links. If you told saint Miles you are going to use a split link he would start using naughty words and saxon language or french. Lol
Alan
I’ve purchased a few things from Mountune recently, and would probably buy more if they stocked more twin cam parts. Their prices on bearings and fasteners are competitive and I’m happy to support a twin cam builder that is at least in the same state.
I did not feel like I needed an extra HD $114 timing chain though. I got mine from QED along with a box full of other bits. No split links in the timing chain. It does seem a wee bit tight though.
I recently fitted my second, possibly third, new chain after nearly 300k miles but I don’t thrash the engine these days. I once returned a new chain (to St Wilkins) as it drooped sideways as much as the old one, which I continued to use.
The A series Cooper engines had poor tension control compared to our TC but I don’t see the need for a double chain so short. Our TC would have more trouble encasing one whereas the A series had a simple pressed steel cover.
I have used IWIS chains on both my Lotus Twincams (no split link), and my Alfa Twincams (split link). Both first class German quality.
Alfa Twincams all have a split link in the chain, (although they are duplex), and I’ve never had any issues with them over 30-odd years of high revving, hard driving use. You just make sure you fit a new retaining clip the correct way round !
I would expect the need for a single or duplex chain is assessed considering the expected life span and the torque to turn the cam or cams. One cam or two doesn’t make much difference to the torque. Valve spring rate, the number of valves and lift does however. I presume the Cooper S engine has higher rate valve springs than the standard A series.
The latest IWIS chains on offer from some vendors have “ended” rollers ie the roller that contacts the gear teeth is made from one flat piece and rolled into a tube - the seam / ends are visible in each roller. Original equipment were endless rollers and I presume heavy duty chains should also use endless rollers.
That may be the difference between Mountune’s chain and others that are available.
When I rebuilt the engine from my Plus 2 about 12 months ago I was going to replace the cam chain as a matter of course. The the chain I bought from QED however had split rather than solid rollers which I wasn’t very impressed with so I ended up reusing the old one which look to be far better quality.
The chain I recently purchased from QED does indeed have split rollers. What are the shortcomings of the split rollers?
The chain that came off is stamped “Renold England” and has solid/endless rollers. I suppose it could always go back on.
I’d suggest that if you had a genuine chain from a reputable supplier (eg. IWIS who supply OEM) you need not be too concerned about split or full circle rollers. I doubt anyone could pinpoint a chain failure due to having spilt rollers. Split rollers and a dodgy brand maybe but not split rollers and a reputable brand. There’s no evidence that split rollers in isolation are any better or worse.
Does IWIS make two types of roller chain - one with ‘split’ rollers and another with solid or continuous rollers without a seam?
His reply just now:
Yes, it’s called a Bush chain, but it’s bigger and heavier, I don’t knowingly sell any to Lotus Twin cam people, do you know to any troubles with the standard chain?
J.
I can only offer the classic “answer a question with another question” - why have the chains moved away from the design that used endless rollers which were originally supplied to Lotus such as “Morse” and “Renold” products? I have original chains and can confirm both Morse and Reynold used endless rollers.
People aren’t too willing to move onto other products when original equipment seems to be better than old equipment time and time again.
Perhaps Jeremy can provide us all with the information to prove that split-end rollers are consistently good for 50,000 miles in road cars and for extended periods in race cars with high valve-train loads? Surely they’ve done the R&D?
Who knows? Either that, or we don’t get to hear about it. Or the chains haven’t had enough mileage put on them to test them.
I have just looked through my stock and I’ve got 1 x brand new Cross & Morse 120 link chain with endless rollers and 1 x brand new Cross & Morse 122 link chain with endless rollers. I can’t remember where they came from though unfortunately.
Only that all the IWIS chains I’ve used on both my Alfa and Lotus Twincams have not had split rollers…
I did buy them from an English (chain / power transmission) company, but I’d have to look through the car’s history file to remind me of who it was…
Hal,
As I am sure you are aware IWIS chains are made in Germany. Was this viewpoint that of the manufacturer? …Or the sole UK agent for IWIS who are now Denis Welch Motorsport (of big Healey fame)?
