Timing chain tensioner fun

Rob Gaskin

Treasurer
Staff member
Site Administrator
Right I'm still trying to understand the points Club members and Kameari have made re Kameari Twin Idler system.

Thanks Jon for the last 3 photos.

Product description: - The head space can be adjusted between 0-4mm so the cam spacer is unnecessary. WHAT DOES THIS MEAN?

I was misunderstanding where the top sprocket sits because I still can't see how this bit of kit negates the need for shims unless it is just referring to chain tension. Are they saying that skimming the head by 4mm (that's a hell of a lot!!) would not be possible with the OEM system because the plunger would be sticking out too far.

As Jon says, with this kit you can't adjust the cam-timing, that is still necessary by repositioning the cam or by using a special sprocket (or by using shims).

Edit - Z Store Description: Cam spacers are no longer necessary as the kit is adjustable up to 4mm. IS THAT SAYING THE SPROCKET MOVEMENT IS 4MM OR IT COMPENSATES FOR 4MM HEAD SKIM?
 
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SKiddell

Well-Known Forum User
I think it’s important to understand what the system is and not what you think it is.

The standard L6 chain tensioning system is adequate for road based driving however when an engine is modified for performance a number of things are changed which mean that the existing chain tensioner system is no longer fit for purpose, for example

Take a stock road engine, as you apply load and then back off, the cam timing can move as much as several degrees +- however it doesn’t matter as valve to piston clearances are huge, the cam is very modest, the compression is safe, so the tensioner is built to cater for this (why over engineer, it costs money)

But Take a well-built performance engine, (high compression, big valves, well matched cam, triple carbies and a decent exhaust) that requires accurate stable cam timing (+- 1 degree) in order optimise compression, burn, scavenging etc. oh and stop the valves hitting the pistons, the standard tensioner cannot maintain this due to that spring loaded piston, Kameari have observed this issue in high performance engines and developed a system to correct this.........which ideally should be used in conjunction with an adjustable cam sprocket and a modified cam.

The head space can be adjusted between 0-4mm so the cam spacer is unnecessary. WHAT DOES THIS MEAN?
It means that you can alter the head thickness by between 0 and 4mm before you run out of adjustment and that cam spacers (shims) are not necessary.

I still can't see how this bit of kit negates the need for shims unless it is just referring to chain tension.
You have just answered this question

with this kit you can't adjust the cam-timing, that is still necessary by repositioning the cam

Of course you can’t it’s not for that.

or by using a special sprocket (or by using shims).

????? Shims should never be used to adjust timing; they are for people who don’t have one of these who otherwise would have a slack chain due to head skimming.

Of course there are those who will say, “well my engines never needed one” and your probably right, this mod isn’t for garage queens, or popping out for a picnic and a spot of chrome polishing, it’s for the performance modifying brigade who wish to tweak and tune their cars and ensure that there stay in tune throughout the rev/power range and that components don’t collide with each other unnecessarily.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Ok Steve thanks - sorted.

I don't like reading things such as (you don't need shims) without more of an explanation. This bit of kit is a much improved chain tensioner but I was reading it as a device to correct/adjust the cam timing as well which it is not - and that's what I couldn't understand.

Jon, Albrecht etc sorry for being so dense.
 
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jonbills

Membership Secretary
Site Administrator
I've had a fun day or so trying to time my cam.
Kent confirmed it is these settings: http://www.kentcams.com/product-details/13/Camshaft/Camshaft/P284-Turbo/ although of course the valve lift is different because of different rockers etc.

Setting to full lift @ 105 deg, It's about right with the sprocket on timing hole one, with 1 extra link of advance. (my earlier thought that a link is 3.3 degrees is rubbish. I now think a link is maybe 15 degrees - so stock settings way out)
settiming.JPG

When I set it to full lift at 105 deg, I was v surprised to discover I had 326 deg duration on the inlet when it should be 284!

After scratching my head for a while and testing, I think it is that this cam expects the same tappet clearance on inlet as the exhaust - so now with 0.010 cold clearance, rather than the standard datsun 0.012, I have 284 degrees and it's basically timed right.

but I'll have to repeat the exercise when I've skimmed the head!
 
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