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I'm redoing some cam timing, however, how much slack should there be on the non drive side, if measured with a straight edge between the two gears, in the photo is this too much?

Where is the best place to get a new good chain?

John

IMG_2815 (2).JPG

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I’m with Jochem on the IWIS chains. Personally I would replace this chain while you will have to remove the chain for valve timing adjustment anyway. 
“standard quality” items are reported on here to wear the tensioner because they are not polished.

Also, while setting the timing, anticipate on the wear you will get during running the engine.

Waldi

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1 hour ago, Waldi said:

Also, while setting the timing, anticipate on the wear you will get during running the engine.

Waldi, what do you mean? for instance, cam @ full lift is 103°. So you set the timing at 102° since the chain will stretch ?? 

Jochem

Edited by JochemsTR
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4 hours ago, John L said:

I'm redoing some cam timing, however, how much slack should there be on the non drive side, if measured with a straight edge between the two gears, in the photo is this too much?

Where is the best place to get a new good chain?

John

IMG_2815 (2).JPG

You need to change the chain and the cogs and before you refit grind the wear grove flat on the back plate reweld and grind flat.

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1 hour ago, Bfg said:

If I might ask .. how do you stop (or greatly reduce) the wear between the tension blade and the timing cover ? 

Pete.  

P1330699s.jpg.3cf1ca95861c50a4074d2ebfe4fed9c1.jpg

You don't.

The spring is a hardened steel, the cover is just mild steel.   But it won't wear its way through!

 

NTC said "You need to change the chain and the cogs and before you refit grind the wear grove flat on the back plate reweld and grind flat."

Those cog teeth do look a bit worn and assymetric, but they will go on working a lot longer.  So it's your choice.

As for the FRONT engine plate, the spring has worn, very slightly, onto the plate's surface.   What possible defect can that cause?  Ignore that 'advice'.

John

Edited by john.r.davies
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Sorry John, I've discarded a couple of timing covers where the tensioner made it's way through to daylight. Plus 1 with Neil on timing cover repair method.  

Mick Richards

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But BFG's wear as so far from that as to make it ridiculous to attempt a potentially warping  'repair' by welding the timing cover.

Was NTC referring to that?   Surely not?    If he was, I still think his advice is way, way over the top!

John

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5 minutes ago, john.r.davies said:

But BFG's wear as so far from that as to make it ridiculous to attempt a potentially warping  'repair' by welding the timing cover.

Was NTC referring to that?   Surely not?    If he was, I still think his advice is way, way over the top!

John

I suspect the wear that Neil was referring to is actually in the front engine plate where the chain will also wear a groove.

Stuart.

Edited by stuart
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23 minutes ago, john.r.davies said:

That's what I thought, and why I thought his advice - unnecessary, shall we say?

Give me strength can you not see the wear marks that the worn out parts have done ? the tensioner has worn the plate and without doing what I said it will snag again,but you know better :lol:

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I’m with Neil on this one. With the new chain the tensioner will operate at a different location and may bind on the burrs or in the groove.

Waldi

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3 hours ago, JochemsTR said:

Waldi, what do you mean? for instance, cam @ full lift is 103°. So you set the timing at 102° since the chain will stretch ?? 

Jochem

Hi Jochem,

yes, one or two degrees. I’m not that brilliant, I think it was Tom Fremont who brought that up some time ago.

So a bit advanced as it will retard over time. 

Waldi

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22 minutes ago, Waldi said:

yes, one or two degrees. I’m not that brilliant, I think it was Tom Fremont who brought that up some time ago.

So a bit advanced as it will retard over time.

I do not agree with this. This is all calculated within the slack coming over time. 
There are various statements in advancing or retarding the timing few degrees. Each one has its advantage. But I will stick to the Manual. 
Jochem

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In my opinion, but I could be wrong,

the absolute different lenght of the timing chain new or worn is not worth the mention.

Why?

When I had both next to each other on my working bench

I was not able to identify them by their different lenght.

You only realize it because "hangs through", like a wire bridge over an canyon.

Edited by Z320
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Hi Jochem,
Here we have a classic example of differing opinions. Let’s agree not to agree on this one.
I do not know if Triumph considered this in their procedure. The same could then apply for ignition timing, valve clearance etc. 

Regards,
Waldi

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Aha, facts, we all like that.

Thanks Pete.

How much degrees camshaft change would this give (crankshaft would be twice that).

Cheers,

Waldi

 

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Hi Pete,

isn't the chain 1.66 mm longer because its 0.84 mm on the pulling side and 0.84 mm on the tensior side?

If this is the case the angle is half as much you calculated?

And on the crankshaft again half the angle?

Ciao Marco

 

Edited by Z320
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1 hour ago, Z320 said:

isn't the chain 1.66 mm longer because its 0.84 mm on the pulling side and 0.84 mm on the tensior side?

If this is the case the angle is half as much you calculated?

..good point, and quite possibly yes ..after all - the other side feels taught (and is a straight run) so all of the 1.66mm stretch is measured in the deflection.  After all the question was by how much would (max) chain-wear alter the valve timing, and not how much total-whiplash there would be.

 

2 hours ago, Z320 said:

And on the crankshaft again half the angle?

I don't feel this is relevant, because the crankshaft sprocket is pulling on the camshaft sprocket via ~ 12 links of the duplex chain. 

The crankshaft and sprocket are fixed, only the tie between the two sprockets has stretched, so the question relates only to how much less an angle has the camshaft subsequently sprocket turned (..the radial difference between new and old chains)  

Pete

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10 hours ago, Waldi said:

Hi Jochem,
Here we have a classic example of differing opinions. Let’s agree not to agree on this one.
I do not know if Triumph considered this in their procedure. The same could then apply for ignition timing, valve clearance etc. 

Regards,
Waldi

Hi Waldi,

if there is scientific evidence to advance the timing due to coming slack, that would be great. So far, I have not identified this. Pete's example shows about 1° degree difference between the 5mm and 10mm slack (5mm is a new chain) @ crankshaft. Korrekt?

David Vizard writes this:

" If you have a choice of two settings which are equally spaced either side of the desired setting, then choose the one most retarded of the two as a delay in inlet valve closure is better than an earlier opening. "

Jochem

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Two stories about ignition timing:

1.

On my pre war motorcycles I start the engine at late, when the engine runs I immediately adjust manual for max advance.

Manual because their engines have no automatic mechanism.

The engine runs more smoothly with that, even on ideling - and I drive all the way on max advance.

2.

A friend of mine realized his new timing gun was not working. We compared with mine - same problem.

We found the automatic mechanism in his distributor glued / fixed by oil and rust on some deg. less than max. 

He drove the car this way probably since he bought it, this was for some years (3-5).

So in my opinion this is no rocket technic.

Edited by Z320
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Pete,

you are my star of the day, somewhere in life I missed the boat to ACAD and similar tools.

Regarding the effect of chain wear on angle: 
I think Marco is correct, in fact it is the elongation in the pulling (straight) part that affects valve timing by retarding is. So  1.46 camshaft degrees @ 10 mm slack, devided by 2 makes 0.73 degrees actual retardance.

On the crankshaft this doubles (half the nominal diameter so 1.46 degrees @ 10 mm (total) slack.

If we follow Jochems logic that we start with 5mm slack on a new chain, the retarding from wear is only half (from 10-5=5 mm), so not that much: 0.73 degree on the crankshaft.

I do not know what the effect of this on performance is.

John,

Sorry for drifting off the original question by John, but hopefully that’s answered too.

Waldi

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