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PostPosted: Sat Aug 01, 2020 4:31 pm 
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I've been looking at my spare Sprint distributor today. I've had to dismantle it to check the vacuum pod and it did seem to be quite stiff. I couldn't move it by trying to rotate the baseplate.
However I filled up the back of the vacuum pod with Plus-Gas and connected the vacuum line to SWK ( an 1850 at idle).
I was expecting the operating rod to move at idle but it didn't ! It only moved when I revved the engine up to about 2,000 rpm. ( i.e when the engine vacuum was lower.)
However the good news was that after a few minutes of revving the engine and dropping back to idle the operating rod moved O.K.
But it was in the direction of retarding the ignition.
Is this correct please ?

Thanks ,
Tony.


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PostPosted: Sat Aug 01, 2020 7:09 pm 
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A couple of weeks ago, I happened to be building a Sprint dizzy out of 2 suspect ones, the first was very poor in the bearings department and also had a huge amount of vertical travel in the cam. The other looked much better on the face of it, but the baseplate, which is supposed to move against itself for the vac, was seized utterly solid (even once completely removed and devoid of points/condenser) and no amount of WD would free it. the vac also seemed suspect, so the good bearinged one got the baseplate and vac from the duff bearinged one and I have one goodun for my trouble, which I regard as a fair result!

But on your problem, I can't imagine anything that would make a vac unit work backwards, are you sure you didn't just mistake the dizzy rotation direction?

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Sun Aug 02, 2020 12:08 am 
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That doesn't sound possible. How do you know it is retarding the ignition? Have you checked it with a timing gun, with the vacuum connected and disconnected?

The vacuum can only pull one way and I don't see how it could be mounted incorrectly.


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PostPosted: Sun Aug 02, 2020 12:59 pm 
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Quote:
I've been looking at my spare Sprint distributor today. I've had to dismantle it to check the vacuum pod and it did seem to be quite stiff. I couldn't move it by trying to rotate the baseplate.
However I filled up the back of the vacuum pod with Plus-Gas and connected the vacuum line to SWK ( an 1850 at idle).
I was expecting the operating rod to move at idle but it didn't ! It only moved when I revved the engine up to about 2,000 rpm. ( i.e when the engine vacuum was lower.)
However the good news was that after a few minutes of revving the engine and dropping back to idle the operating rod moved O.K.
But it was in the direction of retarding the ignition.
Is this correct please ?

Thanks ,
Tony.

I too thought it was manifold vacuum operated and would advance at idle, etc. But I was wrong.

Assuming your 1850 is on SUs, this from sucarb.co.uk/technical-su-carburetters applies:

"On many cars it is found desirable to use vacuum operated ignition advance to obtain optimum part throttle consumption figures. The take-off point for this vacuum is arranged slightly to the air intake side of the butterfly, and in such a position that opening the butterfly allows the throttle disc to pass over the vacuum take-off point so that it then communicates with the manifold depression. By this means the vacuum is small at the distributor during idling and full throttle conditions, and is large at part throttle, being at a maximum when the throttle is open a few degrees. "

So, as the vacuum port it's shut off by the butterfly at idle, ignition timing is going to retard between mid rpm to idle. Is that what you see?

But, wrt checking the diaphragm operation, what's wrong with sucking at the business end and watching the points plate rotate towards you. If it don't move that way, then it's a fault finding exercise seeing if its the VU that's duff or the plate that's jammed, e.g. by leaving off the washer under the cheese head slotted screw that holds the points.

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Sun Aug 02, 2020 4:32 pm 
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Ah... right; thanks for all your comments.
Now the dizzy shaft revolves anti-clockwise viewed from the top. But the vacuum pod ( in the presence of vacuum ) will pull the baseplate clockwise ... so the spark occurs earlier. O.K. I've got it now ! The timing will be advanced !

Thankyou. Brain fade on my part I'm afraid.
Thanks for your link Graham and the explanation.

Cheers All,
Tony.


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PostPosted: Sun Aug 02, 2020 7:28 pm 
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I'm still looking at the possibility of an adjuster acting on the points plate instead of the vacuum unit. I've got something fitted in place of the VU, with a threaded M4 rod, spring, and knurled knob that gives about 1.75 degrees of advance/retard per turn. The attached photo shows it fitted on my third best distributor. The jamnut behind the knurled one is for locking, and the two on the end are to stop it all falling to bits in the case Sod's law applies. The spring is nearly tight in the slot in the dizzy body, so it also stops the arm coming off the pin or the tops of the mechanical advance mechanism pins catching, when it's assembled. There're no mods to the dizzy body, and I used a blanking plate rather than a proper VU.

In the picture, it's set about where it would be with the VU fitted but not active. There's about 8 or 10 degrees of retard available and about 30 degrees more advance. So it should let me set the dizzy wherever I want for best access to the two screws that hold it down, and then set the timing as needed.

But, I did this more to see if I could than to actually try out. And having read a bit more on ported vacuum advance over manifold vacuum, I'm wondering if I need to integrate both, like is on the 25D distributor. I'm fairly sure I can do that if I take a VU apart, move the hole the points plate pin goes through nearer the end of the arm, and put an adjuster screw between the bits.

I would just block the pipe to the vacuum unit off, and see what effect that has on fuel consumption. But I have the issue with the tank leaking a bit when it's nearly full, so I can't measure consumption very well till that's fixed.

So is there anybody using a car without the VU fitted or with one not working who can say what effect on consumption it has, e.g. round town and on the motorway?

Graham


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_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).
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PostPosted: Sun Aug 02, 2020 7:47 pm 
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Joined: Sun Aug 21, 2011 4:12 pm
Posts: 5786
Location: Highley, Shropshire
Quote:
I'm still looking at the possibility of an adjuster acting on the points plate instead of the vacuum unit. I've got something fitted in place of the VU, with a threaded M4 rod, spring, and knurled knob that gives about 1.75 degrees of advance/retard per turn. The attached photo shows it fitted on my third best distributor. The jamnut behind the knurled one is for locking, and the two on the end are to stop it all falling to bits in the case Sod's law applies. The spring is nearly tight in the slot in the dizzy body, so it also stops the arm coming off the pin or the tops of the mechanical advance mechanism pins catching, when it's assembled. There're no mods to the dizzy body, and I used a blanking plate rather than a proper VU.

In the picture, it's set about where it would be with the VU fitted but not active. There's about 8 or 10 degrees of retard available and about 30 degrees more advance. So it should let me set the dizzy wherever I want for best access to the two screws that hold it down, and then set the timing as needed.

But, I did this more to see if I could than to actually try out. And having read a bit more on ported vacuum advance over manifold vacuum, I'm wondering if I need to integrate both, like is on the 25D distributor. I'm fairly sure I can do that if I take a VU apart, move the hole the points plate pin goes through nearer the end of the arm, and put an adjuster screw between the bits.

I would just block the pipe to the vacuum unit off, and see what effect that has on fuel consumption. But I have the issue with the tank leaking a bit when it's nearly full, so I can't measure consumption very well till that's fixed.

So is there anybody using a car without the VU fitted or with one not working who can say what effect on consumption it has, e.g. round town and on the motorway?

Graham
I've not done it with a Sprint, but I ran my mk II GT6 with a vacless TR6 distributor and a Lumenition Optronic for many years on road, Autobahn and track. I can't say I paid much attention to local fuel economy, surrounded as I am by miles of twisty, camera free B roads, I didn't exactly drive in fuel saver mode! But it did in excess of 40 mpg on long motorway runs which I thought was pretty good. I did pay attention to long distance MPG cos the car only had a piddling little Spitfire fuel tank.

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Sun Aug 02, 2020 8:20 pm 
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I'm not sure the Sprint exactly lends itself to fuel economy anyway. Not cos it's inefficient, but cos it just goes so damned well.

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Sun Aug 02, 2020 9:13 pm 
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Re. your adjuster mod.The old Lucas 25d distirbuters on Reliants,and 60s Minis etc.Have an adjuster for fine tuning the timing,opposite the vac unit.


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PostPosted: Sun Aug 02, 2020 10:55 pm 
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Quote:
Re. your adjuster mod.The old Lucas 25d distirbuters on Reliants,and 60s Minis etc.Have an adjuster for fine tuning the timing,opposite the vac unit.
I know, we've a Herald with a 25D4 too. But to do that would need modifying the dizzy body, which I'm not going to do. So it'll have to be a different design that moves the VU relative to the distributor and so moves the points plate round a bit. I estimate I can get it to move about 15 degrees, perhaps 20, with a collar between the diaphragm case and the formed plate that screws onto the body. It's finding something for the spring to press on at the VU end that's giving me difficulties at the moment.

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Mon Aug 03, 2020 12:58 pm 
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Joined: Sun Aug 21, 2011 4:12 pm
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Location: Highley, Shropshire
Quote:
I'm not sure the Sprint exactly lends itself to fuel economy anyway. Not cos it's inefficient, but cos it just goes so damned well.

Graham
We took Mahesh's Sprint on the 2018 RBRR, fitted with a 123 distributor, from what I remember it averaged something like 43mpg over 2166 miles of consistent thrashing, mitigated only by the fact that he runs it (always) on super unleaded and the 123 was set up on a rolling road specifically to use that fuel. So the fuel bill was still rather large!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Mon Aug 03, 2020 1:30 pm 
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Don't really know the 123 dizzy, tho I've heard of it. Does it have a VU or equivalent input?

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Mon Aug 03, 2020 1:46 pm 
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As to running the Sprint on Super Unleaded (or Super Plus): Other than (rare as rocking horse apples) 5 star leaded, what else would you use?

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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PostPosted: Mon Aug 03, 2020 7:07 pm 
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Joined: Sun Aug 21, 2011 4:12 pm
Posts: 5786
Location: Highley, Shropshire
Quote:
As to running the Sprint on Super Unleaded (or Super Plus): Other than (rare as rocking horse apples) 5 star leaded, what else would you use?

Graham
Seeing as the nearest supplier of Super to here (Shell V-Power) is 14 miles away, Sprints around here run on whatever I can get! My own Sprint of course runs perfectly happily on supermarket crap, but that's the Vauxhall engine for you!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


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PostPosted: Mon Aug 03, 2020 9:35 pm 
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Guess I'm lucky to have the choice of Tesco's or Shell's Super Plus 99 Ron stuff or BP's Super (not sure what Ron says about that).

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


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