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

[nicrguy1966]

31 minutes ago, JohnD said:

Your pic from above, niceguy, and it shows the distributor rotated clockwise from the normal position, which is with No.1 lead at 'six o'clock'.    This I presume is the "Very advanced  timing" that you have found necessary.      But why, everyone cries!

The legbone's connected to the ... kneebone, or in this case the dizzie drive shaft is connected to the distributor drive gear and thereby to the cam shaft, and to the oil pump.   The pump has a 'dog' on the end of its shaft that connects to the drive gear.    But when assembling these parts, the pump must go in long before the others.    Then when inserting  the drive gear, the pump shaft must be rotated so that the dogs match, AND the gear must be inserted several degrees away from this orientation, as the hypoid cogs  between camshaft and drive gear rotate the gear as it descends into place.    The objective of this fiddly manoeuvre is to orientate the drive slot in the face of the gear to match the peg in the end of the Dizzie drive shaft, so that the dizzie is then in the correct orientation, with 1 at six o'clock.

Phew!  A picture is worth a thousand words, but I can't find a  diagram of all three (Pump, drive gear, dizzie) as they are always in different sections of the parts catalogue!

What I'm saying is that it is possible to assemble these parts in as many positions as there are cogs on the drive gear!   That's 16, I think, so the possible error is in multiples of 20 degrees.

I suggest that is your problem, nice guy!   Your cam mistiming is trivial, carb tuning likewise, neither could account for the advance you need to use.     It's the Distributor!   Take it out, look at the slot in the face of the drive gear.   It should be in a "five past seven" position , but note, the slot is slightly offset, which should be to the left, thusly:

Alternatively, just move all your ignition plug leads one place counter-clockwise!  Then re-time!

Simples!

John

I agree with Johny.

I have full adjustment of the distributor from firing at TDC to 20 BTDC just by twisting the body. I could do everything you described, but to get it to run smoothly, the spark would be at exactly the same time as it is now.

Edit: I haven't actually checked the ignition timing since adjusting the cam timing, so it might already be "fixed" (wishful thinking).

Edited October 18, 2023 by nicrguy1966

[Iain T]

21 minutes ago, nicrguy1966 said:

Edit: I haven't actually checked the ignition timing since adjusting the cam timing, so it might already be "fixed" (wishful thinking).

The suspense!! Do tell..... 

Dizzy drive slot orientation can't be the problem it only makes the body in an odd or unable to rotate position. My distributor is with 10 degrees advance about 90 degrees anti clockwise to yours but then I have a Lucas. 

Iain 

Edited October 18, 2023 by Iain T

[nicrguy1966]

17 minutes ago, Iain T said:

The suspense!! Do tell..... 

Dizzy drive slot orientation can't be the problem it only makes the body in an odd or unable to rotate position. 

Iain 

I'll be playing with it again after lunch. I'll first check the rocker gaps and replace a bad hose clip while the engine is cold, then fire her up and check/adjust the ignition timing.

I know it needs to be retarded as there was pinking when I had a drive yesterday. I never had pinking before, as the engine seemed to like a stupid amount of advance, so something has already changed.

[Pete Lewis]

yes its going to rain 

i agree where the dizzy body is doesnt matter other than the vac unit can get in the way of any adjustment 

so long as no1 lead is where  the rotor points at no1 tdc compression    ,  it works with 153624 anticlock firing order ht leads from that no1 point 

it is quite easy to fit the drive offset half a turn out when all the fittings, clamp,  dog and slot are a bit old 

it wont help but if its wrong you apply loads to the dizzy shaft you dont need 

Pete

Edited October 18, 2023 by Pete Lewis

[JohnD]

For the love of the gods, TRY IT!   I've proposed a simple fix. You've tried everything else, including things that just aren't  relevant to excessively retarded ignition. 

John

[nicrguy1966]

Today's installment:

1. Fixed the leaky hose
2. Adjusted all tappets so there's no rattle
3. Got the strobe out and found that my "roadside" setting was way off and retarded the ignition to around 16 degrees BTDC (any less than this and the engine started to sound unstable)
4. Went for a drive. A nice smooth tickover at 500 rpm. Lacking a bit of power at low revs, but not as bad as it used to be when set to 13 degrees BTDC. A blip on the accelerator and I could pull away with no problem. At 2000 to 3000 rpm it felt like I had more power than before. I took it to a stretch of motorway and pushed it up above the speed limit without any issues. The lack of power I used to have above 3000 rpm seems to have gone, so nice acceleration in 4th gear from 70 to XX mph (just in case the police are watching!)

I need to use the car Friday so I'll probably leave it as it is until after that, but I suspect I'll be playing with the ignition timing again in the next couple of weeks (and might even double-check the cam timing now I know how "easy" it is!). As an experiment, I plan to set the ignition to 13 degrees BTDC to see how it drives, but not until after Friday.

Edited October 18, 2023 by nicrguy1966

[Ian Foster]

In case it helps, here is the ignition side of my GT6 engine, which also has a Delco distributor.

#1 plug lead at 6 o'clock position using a Pertronix electronic ignition.

If you are using electronic ignition, the distributor will probably be in a slightly different position compared to a points set-up.

Post engine rebuild I discovered that the distributor drive was 180 deg out (slot towards the right), now corrected.

I set the timing at 12deg BTDC using a strobe, which is 10 deg BTDC static. (which is the book figure for the Mk2)

Ian

PS Nic, perhaps you can give us a summary of exactly where you are with this, as I'm a bit confused reading recent posts. 

Edited November 6, 2023 by Ian Foster

[Iain T]

A good result so far well done! 

You have a Aldon electronic ignition which is really Pertronix and a very good bit of kit and made my tick over etc much smoother. The final tweaks may just be carb setting and using at least super grade fuel. I use Tesco Momentum which is 99 octane. Like Ian my ignition is set to 10-12 BTDC (I just loose the 13 degree white line mark under the pointer). 

Iain 

Edited October 18, 2023 by Iain T

[nicrguy1966]

31 minutes ago, Ian Foster said:

In case it helps, here is the ignition side of my GT6 engine, which also has a Delco distributor.

#1 plug lead at 6 o'clock position using a Pertronix electronic ignition.

If you are using electronic ignition, the distributor will probably be in a slightly different position compared to a points set-up.

Post engine rebuild I discovered that the distributor drive was 180 deg out (slot towards the right), now corrected.

I set the timing at 12deg BTDC using a strobe, which is 10 deg BTDC static.

Ian

PS Nic, perhaps you can give us a summary of exactly where you are with this, as I'm a bit confused reading recent posts. 

So clean! Do you ever drive your car? 😁

I'm sure I could rearrange the leads to match yours if I wanted (and twist the dizzy body), but I'm not sure how it would make any difference to the running of the engine.

Where I am is that I have changed the cam timing, and things seem a little better than before, but I still have a little fine-tuning to do before I'm finished. 

[Ian Foster]

4 hours ago, nicrguy1966 said:

So clean! Do you ever drive your car? 😁

2016 and 2018 RBRRs, Isle of Man and a few more good trips, ....so yes!

[johny]

Any conclusion on the patient yet?

[nicrguy1966]

On 31/10/2023 at 19:14, johny said:

Any conclusion on the patient yet?

Given the sudden drop in temperature, I've not spent much time working on the car for a couple of weeks.

Things still to do:

1) Recheck the cam timing now the cars done a few hundred miles (using balance point of 1 & 2 rockers)

2) Try various slight adjustments of the ignition timing to see if I can increase power at <1500 rpm without hurting the power at >1500 rpm. If not, increase idle speed from 500 rpm to 850 rpm.

If I find the cam timing isn't perfect, I'm happy that I can repeat the process of adjustment without the 10 pages of help I needed last time!

[Pete Lewis]

500 is too slow   target is generally 800ish 

500 is ok for strobe ign  timing check so no advance is produced by the centrifugal weights in the dizzy but a bit on the slow side for a normal idle 

Pete

 

[nicrguy1966]

1 hour ago, Pete Lewis said:

500 is too slow   target is generally 800ish 

500 is ok for strobe ign  timing check so no advance is produced by the centrifugal weights in the dizzy but a bit on the slow side for a normal idle 

Pete

 

I know a 500 rpm idle is lower than standard, but the car used to be perfectly drivable at that setting.

Now I have to really rev it and slip the clutch to pull away, and on one occasion when I needed to do a hill start, I was reving up to about 3000 rpm to pull away, otherwise as soon as the clutch bit, the car felt like it was going to stall. Once moving, the car is a better drive than before I changed the cam timing.

Until I've tried a few different ignition timing settings I'm quite relaxed about this issue. It might be a very easy fix.

[Pete Lewis]

with the revised cam setting i would be inclined to time by ear 

advance the dizzy to get the best fastest idle and back it off a bit 

if you have a vac gauge then idle of 18-21inhg  

then dont check the pointers and sleep easy 

3k for an antistall start is extreme  thats just wrong !!

you may find at 500idle  the idle mixture is just set too lean 

Pete 

[Iain T]

On 05/11/2023 at 12:28, Pete Lewis said:

you may find at 500idle  the idle mixture is just set too lean 

I still maintain this was primarily a mixture problem. Before going down any more dark alleys try raising the needle half a turn to richen the mixture and idle at 800rpm. Don't play with ignition and take for a spin. If its better adjust ignition to get optimum setting. 

This way will tell if the original problem was a timing or mixture. 

Iain 

Edited November 6, 2023 by Iain T

[Wagger]

500 rpm is too low for proper oil pressure. My 2.5L idle at 750rpm. Do as Iain annd PeteL suggest.

When setting the dizzy, disconnect and block the vacuum pipe, set the dizzy for maximum idle speed and back off just a tad.

Reconnect the vacuum and try driving. This always works for me. New fuel requires a different setting from the 4 and 5 star that was around when these cars were new. It makes nonsense of static and running settings using a strobe.

I use this method on all old cars and my b-i-l's Minor went like a rocket (well almost) doing 85 mph tops and returning 38mpg on a run after spending a week in my care. (Was that the right word?). It was slightly tuned 1098cc engine. (Disc brakes, ani roll bar and special dampers fitted).

[Iain T]

14 minutes ago, Wagger said:

It was slightly tuned 1098cc engine.

But still the characteristic botty burp out the pea shooter exhaust? It wouldn't be a Minor without that. 

Iain 

[Wagger]

4 hours ago, Iain T said:

But still the characteristic botty burp out the pea shooter exhaust? It wouldn't be a Minor without that. 

Iain 

Quite so. It was a split screen 1955 two door, originally 803cc. I made and fitted an adapter plate for B-I-L to the gearbox maintaining the 'Pudding stirrer' gearstick. It all looked as originally delivered, apart from a servo.

[Straightsix]

Apologies for going off topic, my head is doing cartwheels following this thread, so when Minors got mentioned I got all dreamy remembering mine, Zetec powered!

Thought you might enjoy the pic!

Back to topic…….

[Wagger]

9 hours ago, Straightsix said:

Apologies for going off topic, my head is doing cartwheels following this thread, so when Minors got mentioned I got all dreamy remembering mine, Zetec powered!

Thought you might enjoy the pic!

Back to topic…….

25 years back at a Minor meet, I saw a Minor van with a Toyota MR2 engine and transmission in the rear. Held the back down better than the conventional set up. Others had Fiat Twin cam engines installed. We chose to keep ours as original looking as possible. BIL sold it in 2005 for over £5k.

Apologies to all for the diversion. It is a shame that the Vitesse is so nose heavy, I do not like chuckng mine around anything like as much as the minor.

Getting back on topic, my car only runs really well when fully warmed up. No good messing with anything until it has run for about 20 minutes. Best done in warmer weather too.

[nicrguy1966]

2 hours ago, Wagger said:

25 years back at a Minor meet, I saw a Minor van with a Toyota MR2 engine and transmission in the rear. Held the back down better than the conventional set up. Others had Fiat Twin cam engines installed. We chose to keep ours as original looking as possible. BIL sold it in 2005 for over £5k.

Apologies to all for the diversion. It is a shame that the Vitesse is so nose heavy, I do not like chuckng mine around anything like as much as the minor.

Getting back on topic, my car only runs really well when fully warmed up. No good messing with anything until it has run for about 20 minutes. Best done in warmer weather too.

I'm very happy to wait for warmer weather! My garage isn't heated and I tend to damage my fingers much more working on a car in the freezing cold.

[Straightsix]

Oh no!!! 😱 I’ve just popped out and checked the position of my distributor!

I’ve not got around to checking the timing yet!   Not sure I want to now. (Engine has a different cam fitted) 

nicrguy what have you started 🤦🏼‍♂️

[Iain T]

I think you gear drive needs rotating. It won't effect performance as is but seems 90 degrees out

Iain 

[Wagger]

Straightsix,

If all is running ok, leave it as it is. Your Tacho cable may be better off if all was rotated 60 degrees ACW. That could be straight forward (or not).