Cam belt drive

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Cam belt drive

Postby max midas » Wed Oct 31, 2012 12:37 am

I replaced the cam chain during the last rebuild earlier this year. It was good to feel the 'cammyness' of the engine again after so many years. But within a few months she's gone back to the bland feeling off a not well timed cam - the chain has stretched?
So I'm contemplating going for a belt drive instead, perhaps this one
http://www.shengineering.co.uk/sh/conte ... g-belt-kit

Have read stories of belts going catastrophically, anyone any suggestions?
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Re: Cam belt drive

Postby Hans Efde » Wed Oct 31, 2012 3:03 pm

No a chain is always better than a belt. I have the duplex chain, even better.
http://www.minispares.com/product/Class ... o%20search
Are you sure it's not the cam followers that have been worn? My camshaft and followers were in a horrific state. I am now going to use the Miller oil special for engines with the gears in engine oil.
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Cam belt drive

Postby manifold » Wed Oct 31, 2012 3:25 pm

I agree. Avoid a belt if you can. Why spend £300. Get a decent quality duplex chain kit. One with adjustment will be even better.
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Re: Cam belt drive

Postby lankyjames » Wed Oct 31, 2012 6:29 pm

Also check tappet clearance and torque values on the head bolts :)
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Re: Cam belt drive

Postby max midas » Wed Oct 31, 2012 9:35 pm

If I fit a duplex, do I have to do anything to the cover? Reading the following makes me ask (picture at bottom) - http://www.theminiforum.co.uk/forums/to ... ing-chain/

As to why I thought of fitting a belt, The SH Engineering one offers
perfect cam timing and easily adjusted without removing the crank sprocket.
Cam belt tensioner
Optional VR sensor position
Less harmonic vibration (not sure if a problem on a road going Midas)
Quieter, more civilised ;)

How long will a duplex chain last till it also stretches?

Don't think it's the followers Hans, I had a look at them during the last strip down, they were ok.
I'll check the tappets James, but as I did them when I put the chain in, I presume the problem is the chain.
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Re: Cam belt drive

Postby ACourtney » Wed Oct 31, 2012 10:00 pm

I agree with everyone who suggests fitting a duplex chain. They always stretch a bit and if you read the Vizard book you will see that he suggests setting the sprocket with some advance so that the timing is right when the chain has settled in. I can't recall how much, I would need to check the book which is currently in my workshop.
An adjustable pulley makes setting the timing easy, but I always used offset woodruff keys on my race engines.
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Re: Cam belt drive

Postby max midas » Wed Oct 31, 2012 10:10 pm

Ok, thanks everyone - duplex it is, probably vernier like this
http://www.minispares.com/product/Class ... CBack%20to as I'm not keen on woodruff keys.

Will have to find something else to spend the ££ on now. :lol:

Actually, there's an idea, suggestions on what I could spend the £220 (difference between shiney belt drive and vernier duplex) in order to make the engine more reliable/smoother/faster :D
Any ideas?
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Re: Cam belt drive

Postby Rich » Wed Oct 31, 2012 11:00 pm

1.5 ratio rockers?
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Re: Cam belt drive

Postby Hans Efde » Wed Oct 31, 2012 11:31 pm

max midas wrote:Ok, thanks everyone - duplex it is, probably vernier like this
http://www.minispares.com/product/Class ... CBack%20to as I'm not keen on woodruff keys.

Will have to find something else to spend the ££ on now. :lol:

Actually, there's an idea, suggestions on what I could spend the £220 (difference between shiney belt drive and vernier duplex) in order to make the engine more reliable/smoother/faster :D
Any ideas?


Ditching the distributor and installing a programmable ignition seems to be a big step forward in all aspects.
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Re: Cam belt drive

Postby max midas » Wed Oct 31, 2012 11:52 pm

I agree on both hi lift rockers and programable ignition. I have a megasquirt V3 to install, the trigger wheel is on the pulley, just needs the sensor, coil packs etc buying and installing.
Am watching your injection install closely Hans as that'll be next.
I think I'll get the engine back together first (head has been off for skimming), then megasquirt the electrics, then see about the rockers, though with petrol at £1.40/gallon, sorting out the injection would probably pay for itself sooner :|
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