Simplex Timing Chain
Turbo Mini Forums

I have a simplex timing chain that seems has a lot a slack in it, but no real wear. I have timed the cam and it is 6 degrees retarded.

I know these chains are notorious for stretching… Would it be better to just get an offset key and go with the stretched chain (which I am assuming will not stretch anymore) or replace the chain and have the new chain stretch?

Mike

Are you using a tensioner? if not, The later A+ tensioner is what you need, and probibly the cover as well, the old rubber rings were pants. new chains without a tensioner has slack in it, they dont cost much, mind you, the postage will probibly cost more.

No tensioner... the rubber rings are not doing much of anything. Is it possible to mod my timing chain cover so that I can install a tensioner? Does anyone a a picture of an A+ cover?

Actually looking into a bit more...I would also have to mod the front plate... don't think I am going to do a tensioner...

Is there any harm in running a slack chain with no tensioner?

Edited by Mikes1098 on 27th Oct, 2008.

The front plate mods are very simple.I use a duplex setup and a tensioner and never hear from the chain again.If you can put up with the noise a slack chain will do, but it will be diffucult to get the valve timing right and the cam timing will "flutter" at low engine speeds -not good on a performance engine I think.

BTW, chains dont stretch at all, the pins and bushes wear and this is a continuous process.

used to test old bike chains by bending them sideways, if theres much flex, then its time to replace

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

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Own the day

What I was trying to indicate in response to the quote that "I am assuming it will not stretch any more" was that it would continue to "stretch".Sorry if I offended anyones tender sensibilities.

Yes, they "stretch", whatever people take that to mean and why.....

But they get longer and slacker.....

The rubber rings on early simplex setups are... USELESS.

The early solution was to use a duplex (no rubber rings but the two chains wore more slowly than thesingle) but the A+ solution was probably the best.

The A+ tensioner requires the appropriate backplate - you can't modify the earlier one as the shape of the plate is different - along with a thre part tensioner and a different cover.

It can take a duplex chain as well, with slight modification.

If you are limited to the earlier type (easy to tell the difference as one has ten bolts, the later, eleven), you can run a duplex setup, with slight modification to the bottom two bolts - this was the early solution 20 years ago - but it won't be perfect.

Or just fit new rubber rings and accept that this is the way it used to be.....

Schrödinger's cat - so which one am I ???

where are these rubber rings? I cant visualise?

i use duplex and a+ tensioner

Schrödinger's cat - so which one am I ???

hmm, I may be young, but have never worked on any other a series engines than pre A+... :) Thanks for the answer!

http://www.minispares.com/Product.aspx?ty=...ENSIONER,%20P...

Schrödinger's cat - so which one am I ???

I got it did not feel offended in any way:)

Ahhh, I see your dilema, your new sprocket doesn't have the grooves so you cant fit the rubber rings anyway...

Although Tadge thinks otherwise, I can't see how you could fit the tensioner to an older backplate and get the cover on.





To maintain backwards compatability with the blocks, they used two holes that would have held the old style cover on, to hold the tensioner in place and the extra (11th) hole (on the larger cover/backplate joint) doesn't go into the block, it just uses a nut and bolt.

EDIT - I just realised what Tadge said - you CAN use the same plate (just drill the extra holes) but what I meant was you CAN'T use the same cover..... I was wrong earlier when I said the shape of the plate is different, I should have looked properly first It's an optical illusion because of the gasket outline...

Edited by Rod S on 28th Oct, 2008.

Schrödinger's cat - so which one am I ???

Soo pleased you got there ! I have been mucking about with A series for so long I no longer remember which bits fit which, so I was getting a bit worried that I had misdirected everyone.New cover definitely.

My mistake entirely.....

Mike, if you can get hold of a later cover, the rest is a bargain price in the UK at the moment
http://www.minispares.com/Product.aspx?ty=...R%206%20PIECE...

Schrödinger's cat - so which one am I ???

You could do worse than buy one of TD's new fangled aluminum backplates. AND he is on the same continent

Ahhh, but does he do new fangled aluminium covers to go with them

Schrödinger's cat - so which one am I ???

Edited by Mikes1098 on 29th Oct, 2008.