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Good day. I have recently had my triple webers refurbished and reinstalled. I have tuned them with the obligitory gunson colour tune and balance meter. Now for the timing. Someone once said that the timing should be altered when running triple webers. Can anyone confirm this. If not, what's the recommended settings for the engine. The cams stock by the way. 

Many thanks. 

 

20200729_204449.jpg

Edited by murrayarnold
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Now I am absolutely lost on timing.whats creeping it forward mean. Does that mean advance it. And what does advancing the timing mean. Does it mean go from 11 to 12, or 11 to 10. Timings a black art to me I'm afraid. And how does advancing or retarding effect the engine. 

Sorry if these to some seam stupid questions. 

On 7/29/2020 at 12:08 AM, Mike C said:

Many  people start with 11 degrees before TDC then creep the timing forward until they just get light pinging at low RPM's , WOT.

 

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You generally get more power as you advance the timing, up to a point. From memory -the hot  combustion gas starts burning earlier and as it expands spends more of the stroke pushing the piston down .   If you keep advancing the timing you will reach a point at which the gas mixture just explodes on top of the piston before the piston starts to move down. This explosion is caused knocking or pinging because of the noise it causes. Pinging is very deleterious to engine components as, instead of a gradual force after combustion is initiated there is a sharp pressure rise causing the knocking sound.

The point at which pinging commences is different for each combination of  engine, fuel,   inlet air temperature  temperature . To get the most power you need to advance the ignition as far as it will go without pinging. Pinging is worse at low engine speeds- because the explosion shock wave can develop  easily in gas that is not swirling around- as it does at high engine speeds and at WOT(wide open throttle) because the inlet pressure is high leading to high compression pressures and flame speeds.

Set the timing at 11 deg BTDC and then advance it towards and possibly beyond 12 degrees- until you just hear a slight knocking or rattling sound when you floor the throttle at low speed. 

If you retard the timing too far the combustion gases are still burning when the exhaust valve opens- causing lack of power, burnt valves and generally higher coolant temperatures.

Sorry if this  seems a bit convoluted , but it's a long time since I did Thermo 101.

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44 minutes ago, Andy Moltu said:

You can make minor adjustments with  the little knurled nut.

I have electronic ignition on the car and also triple webbers. There is no vacum hose to the dizzy. Will this have any bearing on timing adjustments

Edited by murrayarnold
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No it shouldn't as such. The vacuum advance uses the same "attachement" as the knurled nut but both work independently.

Sounds like your dizzy doen't use the vacuum advance but the bits are still there even if not in use. (The PI cars too have a vacuum advance device attached but it isn't connected up to the manifold)

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19 minutes ago, SpitFireSIX said:

Somewhere on inlet manifold(s).

Does the car have 7 spark plugs?

Is  the 7th plug  in the inlet manifold ? Looked to be part of the water pump.  I'm not a carb expert but maybe the vacuum line could be connected to the brake booster inlet manifold connection.

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That 7th plugs quite unique. The SU manifold was water cooled. Unlike the webber manifold. So for ease of instalation at the time, 15 years ago, I blanked the pipe with the only thing on hand. A spark plug. Its been there ever since. Hey, if it ain't broke, dont bloody touch it. 

Oh yeah, every car I have with SU carbs gets them tossed un the bin straight away. I detest them. 

Edited by murrayarnold
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Murray(?),

Weber DCOEs don't have provision for vacuum advance. Manifold vacuum is not to be used for this purpose, rather venturi effect vacuum at a port located just behind the throttle plate, as on SU and Stromberg carburetors. No such port exists on the Webers unless perhaps on the 40DCOE151 model currently in production; this is supposedly for a " manometer ".

Stock cam - P.I.? If so, why not use TRIUMPH's recipe which is a 7 degree distributor set to 11 deg.BTDC static time, allowing 25 degrees max. via centrifugal advance. That's what I have in my CP/P.I. cam equipped, triple DCOE engine. 30+ degrees total advance gives pinging on mine.

First I've heard that fitment of Webers warrants a change in timing.

 

Tom

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13 hours ago, Tom Fremont said:

Murray(?),

Weber DCOEs don't have provision for vacuum advance. Manifold vacuum is not to be used for this purpose, rather venturi effect vacuum at a port located just behind the throttle plate, as on SU and Stromberg carburetors. No such port exists on the Webers unless perhaps on the 40DCOE151 model currently in production; this is supposedly for a " manometer ".

Stock cam - P.I.? If so, why not use TRIUMPH's recipe which is a 7 degree distributor set to 11 deg.BTDC static time, allowing 25 degrees max. via centrifugal advance. That's what I have in my CP/P.I. cam equipped, triple DCOE engine. 30+ degrees total advance gives pinging on mine.

First I've heard that fitment of Webers warrants a change in timing.

 

Tom

Many thanks Tom. I will purchase a timing gun and do it in the driveway. I have good hills near by. So will then put her under load and adjust accordingly. Thanks Tom. 

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17 hours ago, Oddball said:

Don’t rely on the pulley marking being accurate. Over the years the rubber annulus deteriorates. Worth checking TDC does match the pulley mark. 

Thats actually something I was considering today. I think i will do exactly that to determine TDC. I have the guage. I will use a white marker to make sure its clear. 

Many thanks

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