GT6 Mk3 only runs well with VERY advanced timing. Any ideas why?

[nicrguy1966]

17 minutes ago, johny said:

And you dont think you have enough knowledge now to correct the problem? Not rocket science although you dont want to rush it...

If sounds very fiddly, and my garage isn't very spacious or well equipped, so even with the radiator out, getting a good view of the front of the engine and clear access will be difficult.

[Pete Lewis]

23 hours ago, johny said:

Have I got that right?

 

been to sleep since i did this but surely the crank remains at tdc its cam sprocket you have to adjust there is no other way ???

you could buy a vernier adjustable sprocket for a good few ££££

 

Pete    

[johny]

yes got to be adjusted on cam sprocket but if you want half a tooth on the crank (to get TDC and cam rocking position) thats only a quarter tooth on the cam because it goes round half as fast. Then of course theres no problem moving the cam sprocket this amount because the offset mounting holes plus the option of using either face allows just that👍 

As you say if you want any finer adjustment its got to be an expensive vernier jobbie...

 

[nicrguy1966]

On 03/09/2023 at 16:55, johny said:

yes got to be adjusted on cam sprocket but if you want half a tooth on the crank (to get TDC and cam rocking position) thats only a quarter tooth on the cam because it goes round half as fast. Then of course theres no problem moving the cam sprocket this amount because the offset mounting holes plus the option of using either face allows just that👍 

As you say if you want any finer adjustment its got to be an expensive vernier jobbie...

 

The mechanic I spoke to has recommended the "vernier jobbie". He thinks it's the only way to set the cam timing accurately.

I'm just waiting for him to have a slot in his garage to fit me in for some professional diagnostics and hopefully a fix.

[Josef]

With regard to 1/4 tooth adjustments, I think more modern gears can only manage 1/2 tooth? Obviously we don’t yet know what the OP has though. 

[johny]

you could be right if the cam sprocket cant be flipped then youre limited to only a half tooth of adjustment...

[dannyb]

Same as my duplex sprocket. Can't be flipped so only half tooth adjustment.

Danny

[johny]

Interesting...

[Pete Lewis]

this has an old gear so a  flip will work  why would anyone make a gear without the basic indexing solution  makes no sense 

sound more a myth than fact 

Pete

[johny]

I can understand with a duplex sprocket as the mounting face has to be offset or it really will be a lump...

[JohnD]

3 hours ago, nicrguy1966 said:

The mechanic I spoke to has recommended the "vernier jobbie". He thinks it's the only way to set the cam timing accurately.

I'm just waiting for him to have a slot in his garage to fit me in for some professional diagnostics and hopefully a fix.

Hmmmmmmmmmmm!

As said above, even without a 'flip', you should be able to set your timing to within half a tooth. (Can't recall what that is in degrees!) When your original complaint indicates it misset by more than that.   Verniers are for people who want to advance/retard by micro amounts.

John

[nicrguy1966]

17 minutes ago, JohnD said:

Hmmmmmmmmmmm!

As said above, even without a 'flip', you should be able to set your timing to within half a tooth. (Can't recall what that is in degrees!) When your original complaint indicates it misset by more than that.   Verniers are for people who want to advance/retard by micro amounts.

John

I must admit I did think it was more for his convenience than absolutely necessary for a road car. It's not like I'll be striping the engine and tuning it on a regular basis.

[Josef]

12 hours ago, Pete Lewis said:

this has an old gear so a  flip will work  why would anyone make a gear without the basic indexing solution  makes no sense 

sound more a myth than fact 

Pete

Same reason they’ll make synchro rings that’re not round…

I do have no experience of this myself, so can’t say it’s true for certain, but I can believe something like this would be done as a cost saving exercise.

[nicrguy1966]

Before I pay someone to look at it, there was one suggestion earlier that I've not investigated and I think it's within my DIY skillset, and that's to check if the distributor is "one tooth out".

How likely do people think this could cause the problem? I'm doubtful as I can adjust the ignition timing all the way from 13 degrees BTDC to 26 degrees BTDC by twisting the distributor body, so what difference would changing the way gears at the base of the distributor fit make?

[Iain T]

19 minutes ago, nicrguy1966 said:

How likely do people think this could cause the problem

It's not as you just rotate the dizzy to alter the timing.

You have to get the valves working at the correct time in relation to the crank/piston or the engine will never work properly. 

Iain 

[johny]

yes youve already proved with the strobe the spark comes at the right time relative to the position of the piston so thats not the problem...

[Pete Lewis]

the dizzy has no idea where the spark is needed  you can have the gear miles out you just rotate the body to get  your number1 TDC +10deg advance and No1 HT lead where ever it happens to fall.but must line up the rotor and the cap terminal  the only deciding factor is the vac unit will foul the engine block/alternator etc if the body needs to be extremely out  if the HT leads shown as no1 at 11oclock happen to be at 3 oclock who cares so long as the 153624/1342 are in the right order 

im not a originalist   just a realist 

but the cam timing and ign timing are all/both needed at the right time 

Pete

 

 

[Wagger]

Itwill be nothing todo with the distributor. That will just complicate matters. If yo have a single row chain just flip the sprocket over as all the good guys have suggested.

[johny]

Any advance (pun intended) in this intriguing case?

[nicrguy1966]

2 hours ago, johny said:

Any advance (pun intended) in this intriguing case?

I spoke with 2 garages that I know have experience working on older cars. The first didn't seem to have a clue about my car and I felt I'd be paying him to learn more than fix anything.

The second was clearly very knowledgeable but seemed to want to create a much bigger job than just fixing my cam timing (seemed very keen on fitting a different cam shaft as well as a vernier gear on the cam shaft). The idea of just flipping the gear over seemed totally beneath him.

So I've decided to try and do it myself, and I'm just waiting for a good time when I don't need the car for at least a week and I'm less busy at work.

The only question remaining is whether to do it in my tiny, one car garage, or take it to a workshop with much more space, a hydrologic lift, but much more pressure to get the whole job done in a single day. Otherwise the car will be stuck there, undrivable, and about 45 minutes walk from home.

Edited September 23, 2023 by nicrguy1966

[JohnD]

Guy,

You have established that the cam timing is out!  Well done!  Now to bite the bullet and correct it, and you can do this yourself!

But prepare!   You don't want to realise that you need parts when you want the car back on the road.  A new timing cover gasket, and I suggest a new crank oil seal while that is off the car.    One of the most fiddly jobs is to ensure the timing chain tensioning spring is in place when putting the cover back on.    A wire hook like this is helpful - use thick wire! Mine is made from an old coat hanger!    "A" should be the width of the chain, Singlex (as probably on a GT6) or Duplex.   Use it to hold the spring against the cover as you replace it.

You will probably need to remove the radiator for ease of access, so antifreeze to replace the coolant, and (why not?) new rad hoses too.

Then actually doing the timing.     The 'usual' method involves lining up marks on the cam and crank sprockets, but rebuilt engines may have replacement sprockets without marks.   Then, you must use the 'classical'  method that uses protractor wheels on crank and cam, or else ELoO!   I think I have posted for you a link to my article on Sideways, but that uses two dial gauges which you may not have.  There is an alternative methods, one in which you set the valve gaps wide and then check for equality at TDC Look it up, I thin k it;s in the WSM), or else you can use a spirit level!   See: https://sideways-technologies.co.uk/forums/index.php?/topic/9639-a-new-method-of-cam-timing/#comment-134275     There I pictured the method with the head off, but you could use it on the rockers with ease.

Good luck!

John 

[johny]

Yes having time to do the job is important as any pressure is likely to make things more difficult and/or go wrong. I would use your garage, doing it step by step and consulting on here about any doubts or confirmation that might be required...

[nicrguy1966]

3 hours ago, JohnD said:

Guy,

You have established that the cam timing is out!  Well done!  Now to bite the bullet and correct it, and you can do this yourself!

But prepare!   You don't want to realise that you need parts when you want the car back on the road.  A new timing cover gasket, and I suggest a new crank oil seal while that is off the car.    One of the most fiddly jobs is to ensure the timing chain tensioning spring is in place when putting the cover back on.    A wire hook like this is helpful - use thick wire! Mine is made from an old coat hanger!    "A" should be the width of the chain, Singlex (as probably on a GT6) or Duplex.   Use it to hold the spring against the cover as you replace it.

You will probably need to remove the radiator for ease of access, so antifreeze to replace the coolant, and (why not?) new rad hoses too.

Then actually doing the timing.     The 'usual' method involves lining up marks on the cam and crank sprockets, but rebuilt engines may have replacement sprockets without marks.   Then, you must use the 'classical'  method that uses protractor wheels on crank and cam, or else ELoO!   I think I have posted for you a link to my article on Sideways, but that uses two dial gauges which you may not have.  There is an alternative methods, one in which you set the valve gaps wide and then check for equality at TDC Look it up, I thin k it;s in the WSM), or else you can use a spirit level!   See: https://sideways-technologies.co.uk/forums/index.php?/topic/9639-a-new-method-of-cam-timing/#comment-134275     There I pictured the method with the head off, but you could use it on the rockers with ease.

Good luck!

John 

Good tips about the crank oil seal and the timing chain. I hadn't thought of those, I only considered the timing cover gasket.

When I was speaking with the mechanic that did seem to understand the Triumph engine, he said that the marks on the crank and cam gears would have been put on by whoever rebuilt the engine when it was reconditioned. So if they put the engine together wrong, the mark would also probably be in the wrong place. 

I'll have to rely on setting the cam timing using another method, such as finding the "balance point" (described in the WSM).

I'll order some parts next week, then it's just a case of finding the right time to pull the engine apart.

[johny]

Obviously once the covers off but before undoing anything else look for marks on the sprockets and backplate as they might be present and indicating an error. If they are then correct the error and finally check the timing by an alternative method...

I suspect the components will all be in good condition (however inspect everything closely) but apart from the gasket and seal the chain tensioner is the item that wears fastest and as new ones are pretty cheap you might want to have one spare.

[nicrguy1966]

I've ordered the gasket and oil seal from Canley Classics. I don't think I'll need to change the tensioner as the engine was reconditioned around 12 years ago (when the timing problem probably started).

Now I just need to wait for the postie, and for a gap in my work schedule (and probably plaster a wall that's also on my to-do list, and is higher on my wife's list of priorities!)