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


nicrguy1966

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1 hour ago, nicrguy1966 said:

Whether they're doing the right amount of advance at the right time is not possible for me to test at home.

The Distributor Doctor is your best option for refurbishing your dizzy. He checks and calibrates the advance curve. 

Iain 

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40 minutes ago, nicrguy1966 said:

He only mentioned Lucas distributors on his website. Does he also do Delco?

Not sure best to phone but as Johny posted you can roughly check yourself up to say 3000rpm. After that the neighbours might start yelling😁 

Iain 

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1 minute ago, Iain T said:

Does it tick over OK at say 6-800 rpm?

Yes, lovely and smooth. I can slow it down to about 500rpm without any issues.

The problems occur at >3000rpm where it lacks power (probably due to the spark being stupidly advanced).

With ignition set to 13 BTDC at idle (the Haynes Manual recommended setting, but very different from the numbers provided above), it lacks power at all revs.

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read  the test data in the WSM carefully most Dizzy testing figures  is done DECELERATING so you measure the degrees reducing revs not as you expect raising the revs 

this catches a lot out 

just be sure of the test data and HOW not all are like this but you do need to know  Ha!!!  just another learning curve to combat the peaceful snoozing 

Pete

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1 hour ago, nicrguy1966 said:

He only mentioned Lucas distributors on his website. Does he also do Delco?

There is H&H ignition systems that do Delco, though when I got mine done it was cheaper to go via the club shop than direct

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10 minutes ago, johny said:

Dont forget those workshop manual figures are added to the static setting as the weights fly out under centrifugal force so that would give total 35* max...

That makes a lot more sense now. I did wonder about 0 at 800rpm, it didn't sound like any setting I'd ever seen before.

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34 minutes ago, nicrguy1966 said:

Yes, lovely and smooth. I can slow it down to about 500rpm without any issues.

The problems occur at >3000rpm where it lacks power (probably due to the spark being stupidly advanced).

OK a curve ball which may be a load of rubbish. In the search of 500bhp and 1000ft/lbs of torque out of my tuned Vitesse engine I tried timing it using the manifold vacuum technique. I was surprised that at tick over it did indeed run fine at around 20 degrees advance but did pink a slightly under load. Then I read or someone on the forum posted that with K&N less restricted air filters the vacuum at tick over is effected so I returned to 13 degrees. However at that setting the engine was nowhere near as good as it should be. In fact on a rolling road power dropped like a stone over 4000rpm. 

The answer was leaky carbs/gasket joint and more importantly getting the correct needle and mixture! I've posted in fuel section my woes but now it's 95% correct the difference is huge absolutely transformed the performance and timing back to 13 degrees. 

Iain 

Edited by Iain T
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14 minutes ago, Iain T said:

OK a curve ball which may be a load of rubbish. In the search of 500bhp and 1000ft/lbs of torque out of my tuned Vitesse engine I tried timing it using the manifold vacuum technique. I was surprised that at tick over it did indeed run fine at around 20 degrees advance but did pink a slightly under load. Then I read or someone on the forum posted that with K&N less restricted air filters the vacuum at tick over is effected so I returned to 13 degrees. However at that setting the engine was nowhere near as good as it should be. In fact on a rolling road power dropped like a stone over 4000rpm. 

The answer was leaky carbs/gasket joint and more importantly getting the correct needle and mixture! I've posted in fuel section my woes but now it's 95% correct the difference is huge absolutely transformed the performance and timing back to 13 degrees. 

Iain 

It's amazing how an odd ignition timing can lead in so many different directions! Cam timing, warn distributor and now fuel/air mixture!

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2 minutes ago, nicrguy1966 said:

It's amazing how an odd ignition timing can lead in so many different directions! Cam timing, warn distributor and now fuel/air mixture!

It is natural to suspect cam timing and I'm sure now you've corrected the minor error it will be better. I can only relate my experience which given the head etc required a lot more fuel and timing wasn't the problem. If you lack power after getting it back together try turning the carb adjuster half a turn and ignition at 13 degrees. I think you have a Mk2 which if your engine is standard has 6AC needles. 

Edited by Iain T
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38 minutes ago, Iain T said:

It is natural to suspect cam timing and I'm sure now you've corrected the minor error it will be better. I can only relate my experience which given the head etc required a lot more fuel and timing wasn't the problem. If you lack power after getting it back together try turning the carb adjuster half a turn and ignition at 13 degrees. I think you have a Mk2 which if your engine is standard has 6AC needles. 

It's a late Mk3, and I don't think there is any manual adjustment on the carbs. Changing the needles is the only way to change anything (and fixing any possible leaks around the inlet manifold). 

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24 minutes ago, johny said:

yes and quite a bit of tolerance on the figures as well. Anyway when is the big start up?

After lunch if all goes well.

I'm thinking of starting it up without a radiator or fan, just for a few seconds. If it doesn't start, I'll try a few times with different ignition timings, and if it still doesn't start, I'll have to consider reversing everything I've done over the last few days!

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