13 replies to this topic

[Thelimes79mini]

im installing a new duplex timing gear set up with my new cam
do you still use the original chain tensioner

Thanx the Lime

[Cooperman]

No, especially if you want to use high-ish revs as the tensioner pad can break up.

[dave-88_123]

it depends on the kit no if its a genuine AE set but cheaper ones do use a tensioner you can tell by the amount of slack in the chain when fitted

[Cooperman]

The issue with the tensioner is that with a single chain the tensioner pad sits right in the centre of the chain and overhangs is slightly on each side. This means that the tensioner takes the load equally on each side. With the duplex chain the tensioner sits only on the centre of the chain and this can cause wear just in the centre of the pad which can then break up.

[Wil_h]

This topic has come up befor on TM http://www.turbomini...p=vt&tid=463432 there is no consensus. Advantages and disadvantages to running with and without, Based on available info, you need to decide what is most suitable for you.

[Cooperman]

I've seen one engine with a duplex where the tensioner pad had broken up and another where it was about to. You know, I wnoder if it is partly caused by what happens when the engine runs-on backwards as some engines tend to do when switched off. Both the ones I had the issue with had high comp. ratios. That's just a guess. What do you think chaps?

[TopCatCustom]

Sounds feasible, wouldn't take much of a backwards kick to damage it.

[HUBBA.HUBBA]

Hi chaps, out of interest how firm do you put the tensioner against the chain when you bolt it in? I' m concerned about making to ''too' tense. (Duplex)

[ACDodd]

I have always used a tensioner with no problems, even on competition engines.

AC

[HUBBA.HUBBA]

I have always used a tensioner with no problems, even on competition engines.

AC

But is it pressed hard against the chain, so the chain is super firm or do you give it abit of slack?

[Wil_h]

Just touching.

If it's too tight it will break. Which may be the reason the ones cooperman saw were broken/breaking.

[ukcooper]

What's dose the tensioner do beside taking a little slop out of the duplex chain and making a it a little quiter maybe, Dose it affect the timing or put wear on the gears ??. Im just intrested thats all.

I never fitted the tensioner as it seemed one less thing to break.

[Stevie W]

The tensioner runs on the "slack" side of the chain to take up any "slop" as you riightly state.
Agree with others that if the engines "kicks back" after switch off and runs in the other direction, then the chain will wear the tensioner fairly quickly!
I've personally had no issues with a tensioner on a duplex chain but do understand the implications of doing this.
I set up the tensioner to "just" take up any slack, so in effect the chain just "runs" over the tensioner pad and since I don't use a lot of revs I do not suffer with any problems.
You could imagine that the tensioner may help a little with keeping the cam timing where it was set since the slack side of the chain has a little pressure to stop it whipping about with the engine running.
Its horses for courses really!!!
Steve

Edited by Stevie W, 17 December 2012 - 06:41 PM.

[Cooperman]

In the end it's just personal choice really. The engines I've had where the pad had in one instance disintegrated and in the other was cracked were both on high-revving high-compression engines which had probably 'windmilled' backwards during their life and I'm now fairly certain it's this which caused the failures I've seen.
Also they may have been set too tightly when built (I didn't build either of them, I'll quickly add!).