Timing chain
Turbo Mini Forums

I've always used a tensioner with the duplex - wouldn't run one without - thats where your stretch is coming from - the chain "whipping" during rotation - when was the last time you saw a car with a timing chain not running a tensioner - and I don't care how short the mini one is it will never be tensioned perfectly out of the box - especially if the block is line bored!!

If Carling made Mini engines
it would probably be like this one!

I seriously doubt it!

heres my 2p's worth

i think it will be an almost immediate process that happens within the few mins of running

mainly the chain wearing in from manufacture, i.e high spots/rough/uneven edges on mating surfaces bedding in

and then it will of course stretch with time also

*edited to add really rough workings*

2 degrees of movt on the crank gear is prob about 0.5mm at its outer radius.

the length of chain across the tangent of both cogs is about what 15cm? or 150mm

so the chains stretched about 0.3%?

Edited by joeybaby83 on 2nd Jul, 2008.

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

I seriously doubt it!

As normal Paul it looks like it's one of them things that every one finds different

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

On 2nd Jul, 2008 Miniwilliams said:
As normal Paul it looks like it's one of them things that every one finds different

I seriously doubt it!

Timing Chain stretch is a Very real problem escalated very much by 1.5 roller rockers and heavy valve springs I have always gone with Swifty on this and retarded the cam timing by 1.5 deg,
I have tested this very simple using a dial gauge it is a long process but pays of,
The method for testing this phenomenon is as follows,
1. setup you timing as normal
2. put the dial gauge on each inlet rocker in turn note the max lift figure and crank angle at which this accurse and this angular figure together and divide by 4 and note this figure.
3.run the engine for between 10 and 20 hours.
repeat step 2 and note your figures.
4.run the engine for a further 10 to 20 hours and again repeat step 2 and note your figures,
5.again run the motor for a further 20 hours and note the figures.
6 add the figures you get at step 3 for the 4 inlet valves and divide by 4 repeat this step for the figures you get on step 4 and 5 then add these three figures together.
7. take the figure you get in step 6 and subtract these from your original figure in step 2 and you will have a real world figure for timing chain stretch minus cam shaft wear.
regards,
Paul.

doesnt it mention it in the yellow bible too??

if its such a problem, then why doesnt to the top engines run belts.. is it just a cost thing?

Anton i see what your saying but things have moved on a lot since the yellow bible was out, parts are all probably better made now to.

Best 1/4 mile 13.2 seconds @116 mph
First 5 port miniturbo to make over 200 bhp on a carb?
First 5 port miniturbo to make over 200 bhp on Injection?

http://www.mattwoodsphotography.com

Swifty got back to me and said this chain that he is supplying now will stretch 1 degree.
Ill give it some miles this week and recheck it next week

Paul

I seriously doubt it!

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