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

[nicrguy1966]

Sorry if this is covered elsewhere, I did look, but didn't see anything similar.

I'm still investigating this issue, so I already have a partial "to-do" list of things to look at, but I was hoping for some input from others to rule in or out various causes.

The problem is that when I set the ignition timing to what it "should" be (13 degrees BTDC), the car runs terribly at all revs. No power. Stalls easily when pulling away, feeble acceleration, needs really high revs to do anything. This has caused me problems in the past, for example when I was at the South of England meet one year, there was a company tuning cars, and I hardly made it out of the field without needing to go back and ask them to reverse everything they'd done!

By trial and error, I've found a setting that makes the car drivable, but it's about 20-23 degrees BTDC at idle (Dynamic measurement, I have a timing strobe). I assume this isn't giving me the performance Triumph intended.

I still need to test the vacuum advance and centrifugal advance to make sure they're both doing something close to what they're expected to do. 

Major changes since it left the factory:

1. Running unleaded fuel
2. Twin pipe stainless steel exhaust (original exhaust manifold)
3. K&N air filters
4. Aldon electronic ignition

At one point, I wondered if the timing marks on the crack-pully could be wrong, but from looking at the Haynes manual, it looks like there's a woodruff key, so should only fit in one position.

Does anyone have any ideas about what else could make the engine only run well so far from the original setting? Is it a problem I need to fix, or just set it to what works and warn all future mechanics?

Thanks in advance.

[Pete Lewis]

i would check the timing /damper ring on the front pulley 

the rubber bond breaks down and the timing ting can move/rotate on the pulley   

so need to acurately get no1 at TDC and see just what the timing marks show ,,,,can be miles out 

Pete

[Colin Lindsay]

You could have a tooth out on the distributor drive, or again, as Pete says, the timing marks on the pulley aren't right. My Mk1 ran very well at some strange timing setting, when close to the factory setting it just died. I adjusted it by ear, and by actual driving and disregarded the readings altogether.

[johny]

I wonder if your dizzy needs an overhaul. If the centrifugal weights are stuck and dont fly out to advance the timing as your revs increase the timing wont advance and performance will be poor. By advancing the timing at idle you are partially compensating for this but its not the solution....

[nicrguy1966]

28 minutes ago, Pete Lewis said:

i would check the timing /damper ring on the front pulley 

the rubber bond breaks down and the timing ting can move/rotate on the pulley   

so need to acurately get no1 at TDC and see just what the timing marks show ,,,,can be miles out 

Pete

One idea I had was sticking a screwdriver in the spark plug hole for cylinder 1 to see if I could "feel" TDC from the piston position. Not at all accurate, but hopefully I'd be able to tell if the timing marks are 10 degrees or more out.

[Nigel Clark]

14 minutes ago, johny said:

I wonder if your dizzy needs an overhaul. If the centrifugal weights are stuck and dont fly out to advance the timing as your revs increase the timing wont advance and performance will be poor. By advancing the timing at idle you are partially compensating for this but its not the solution....

I'm also suspecting seized auto advance mechanism, struck in the retarded position. Take the distributor cap off and try twisting the rotor arm....

Does it move one direction and tend to spring back when released? If not, it's seized.

Nigel

[nicrguy1966]

13 minutes ago, johny said:

I wonder if your dizzy needs an overhaul. If the centrifugal weights are stuck and dont fly out to advance the timing as your revs increase the timing wont advance and performance will be poor. By advancing the timing at idle you are partially compensating for this but its not the solution....

Yes, that's on my to-do list.

Last time I tried adjusting the timing with a strobe I was on a deadline and didn't get to run it with/without the vacuum advance, and revved to see if the centrifuge weights were doing their thing.

I wish I'd taken the time as my rush to get the car ready for a drive meant I drove a car that was awful and I ended up doing a roadside timing adjustment without the strobe to get home.

[nicrguy1966]

1 minute ago, Nigel Clark said:

I'm also suspecting seized auto advance mechanism, struck in the retarded position. Take the distributor cap off and try twisting the rotor arm....

Does it move one direction and tend to spring back when released? If not, it's seized.

Nigel

Thanks, I'll try that too.

[nicrguy1966]

34 minutes ago, Colin Lindsay said:

You could have a tooth out on the distributor drive, or again, as Pete says, the timing marks on the pulley aren't right. My Mk1 ran very well at some strange timing setting, when close to the factory setting it just died. I adjusted it by ear, and by actual driving and disregarded the readings altogether.

I'm not sure I understand the first point about the distributor drive tooth, but I've been following the second point for about a year (disregarding the readings, and setting it by trial and error)!

I just wondered if there was an easy fix, and if I'm losing a whole herd of horse power.

[johny]

Has the engine been left unused for sometime and not had its routine dizzy lubrication?

[nicrguy1966]

17 minutes ago, johny said:

Has the engine been left unused for sometime and not had its routine dizzy lubrication?

No and yes!

It has been used regularly (never more than 2 months between drives), but I have neglected routine maintenance as it only does about 1000 mile a year.

On the other hand, this isn't a new problem, it's something that I've been ignoring for years.

Edited August 16, 2023 by nicrguy1966

[johny]

Wow it would put me off driving and dont suppose it helps fuel consumption either!

[nicrguy1966]

1 hour ago, Nigel Clark said:

I'm also suspecting seized auto advance mechanism, struck in the retarded position. Take the distributor cap off and try twisting the rotor arm....

Does it move one direction and tend to spring back when released? If not, it's seized.

Nigel

I just did the above test, as well as sucking on the vacuum pipe. Everything seems OK with the distributor.

1. The rotor arm moves about 1/4 of an inch and springs back in one direction, with no movement in the other direction.
2. When I suck on the vacuum pipe, I can see stuff moving inside the distributor.

So with static tests, no distributor problems are detected.

[Colin Lindsay]

54 minutes ago, nicrguy1966 said:

I'm not sure I understand the first point about the distributor drive tooth

If the dizzy and toothed drive has been removed, then it has to be replaced in the proper orientation to make sure the rotor arm is at the correct spot for the spark. It's very easy to replace in an incorrect alignment, as the teeth are angled so you think you're dropping it back in correctly, but it's actually rotating as it drops and so settles into the wrong spot. If it's replaced even one tooth out, the timing marks are going to be off by a multiplication of that tooth. The general guide is: set engine at TDC, drop the drive gear in with the offset slot towards the front, and a line drawn through the slot will point to no 9 pushrod tube.

[nicrguy1966]

22 minutes ago, johny said:

Wow it would put me off driving and dont suppose it helps fuel consumption either!

Once set "by ear" rather than to recommended settings, it's a nice drive. My problem is that I'd like to know why it's so far from the factory default settings.

[nicrguy1966]

7 minutes ago, Colin Lindsay said:

If the dizzy and toothed drive has been removed, then it has to be replaced in the proper orientation to make sure the rotor arm is at the correct spot for the spark. It's very easy to replace in an incorrect alignment, as the teeth are angled so you think you're dropping it back in correctly, but it's actually rotating as it drops and so settles into the wrong spot. If it's replaced even one tooth out, the timing marks are going to be off by a multiplication of that tooth. The general guide is: set engine at TDC, drop the drive gear in with the offset slot towards the front, and a line drawn through the slot will point to no 9 pushrod tube.

So if I understand you correctly, if the distributor is fitted "one tooth out", when at "factory recommended timing" the rotor arm will be in the wrong position for the connection on the inside of the distributor cap. By changing the timing several degrees more Advance, I'm losing power, but getting a spark that actually makes it to the spark plug?

Have I understood your coment?

Edited August 16, 2023 by nicrguy1966

[Pete Lewis]

if you dont belive the timing rings move ask JohD he has produced as aproject a 6cyl drive test rig to prove the harmonics of these dampers and the moving timing ring

its far more common than many realise  when we got the 1600 many years back you could rotate the timing marked ring around to suit whatever you didnt want

it took a bit of fathoming out where the wild timing  errors were coming from the proble is you cant re adhere the  ring and they are becoming rocking horse pooh !!to replace

Pete

[johny]

25 minutes ago, Colin Lindsay said:

If the dizzy and toothed drive has been removed, then it has to be replaced in the proper orientation to make sure the rotor arm is at the correct spot for the spark. It's very easy to replace in an incorrect alignment, as the teeth are angled so you think you're dropping it back in correctly, but it's actually rotating as it drops and so settles into the wrong spot. If it's replaced even one tooth out, the timing marks are going to be off by a multiplication of that tooth. The general guide is: set engine at TDC, drop the drive gear in with the offset slot towards the front, and a line drawn through the slot will point to no 9 pushrod tube.

I think Colin if youre seeing the timing is correct with a strobe then there cant be much wrong with the distributor gear. Of course as Pete says if the pulley marks have moved then all bets are off😁

[nicrguy1966]

2 minutes ago, Pete Lewis said:

if you dont belive the timing rings move ask JohD he has produced as aproject a 6cyl drive test rig to prove the harmonics of these dampers and the moving timing ring

its far more common than many realise  when we got the 1600 many years back you could rotate the timing marked ring around to suit whatever you didnt want

it took a bit of fathoming out where the wild timing  errors were coming from the proble is you cant re adhere the  ring and they are becoming rocking horse pooh !!to replace

Pete

It's not that I don't believe anything anyone has written, the more suggestions the better.

I need a to-do list of things to try. It was easy to test the vacuum and centrifugal functions, so I did that straight away. I'll need a bit more time to try and figure out if the timing marks on the pully have moved, so that's a job for the weekend.

[nicrguy1966]

13 minutes ago, johny said:

I think Colin if youre seeing the timing is correct with a strobe then there cant be much wrong with the distributor gear. Of course as Pete says if the pulley marks have moved then all bets are off😁

Yes, I was confused by this too.

The timing strobe was firing correctly at the factory settings, so the spark was reaching the sparkplug. Given the amount of effort to check the fitment of the distributor, this will be towards the end of my to-do list! (and I still don't fully understand how fitting the distributor one tooth out would cause the symptoms I'm seeing).

[dougbgt6]

I don't use a strobe, I do it by ear or vacuum gauge. !3 BTDC is for 5 star, sadly no longer available, we had to readjust for 4 star, but now 5% ethanol means further adjust and 10% even more. There will also be slack due to wear in the system so the timing marks are meaningless. As Pete says the ring can slip. (I've seen John's machine to!) 

Doug

[nicrguy1966]

30 minutes ago, dougbgt6 said:

I don't use a strobe, I do it by ear or vacuum gauge. !3 BTDC is for 5 star, sadly no longer available, we had to readjust for 4 star, but now 5% ethanol means further adjust and 10% even more. There will also be slack due to wear in the system so the timing marks are meaningless. As Pete says the ring can slip. (I've seen John's machine to!) 

Doug

So if it's workng OK, don't worry about what the strobe says?

That only works if every mechanic that tries to "tune" the vehicle in the future doesn't set it to factory defaults and make the car undrivable!

[dougbgt6]

13 BTDC is no longer valid, it doesn't work with modern fuel. My manual says front tyres 22, which is dangerous for modern tyres, mine are at 30. There are many things in the manual that should be looked at through modern eyes, does the manual say to change the brake fluid every 2 years? No, but we now know it should. 

Doug

[nicrguy1966]

31 minutes ago, dougbgt6 said:

13 BTDC is no longer valid, it doesn't work with modern fuel. My manual says front tyres 22, which is dangerous for modern tyres, mine are at 30. There are many things in the manual that should be looked at through modern eyes, does the manual say to change the brake fluid every 2 years? No, but we now know it should. 

Doug

So what is the general opinion on the correct timing for our cars with modern fuel?

[Paul H]

3 minutes ago, nicrguy1966 said:

So what is the general opinion on the correct timing for our cars with modern fuel?

Pretty sure mine is 19 / 20 btc in my mk 2 Vitesse 

Paul