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HRA · Aug 3rd, 2020, 09:18

Thanks Ron-Kwas; that's pretty much how I visualised it. My distributor probably has a slightly different graph since the number ends 077. Looking at the 099 graphs, the heavy spring governs the last 5 degrees of advance. I had to back my timing off by about 10 degrees to stop the pinking (or pinging) so I maybe the change of slope of the 077 graph to starts earlier?

Mechanically my work-around seems to be holding-up. I tried to get some photos but the auto-focus on my phone wasn't having it - get close enough to see and all it wants to focus on is the background! However, even though the heavy spring is back in operation I still need to retard the timing nearly 10 degrees to be sure of no pinking.

That's set me wondering about the other causes of pinking:[LIST][*]Spark plug too hot[*]Low-octane fuel[*]mixture too weak

I'm running NGKSPARKA007037 plugs - I think they're pretty standard and I haven't seen any of the white deposits and damage that overheating causes.

I do usually buy the basic 95 RON unleaded fuel. In the past I did try higher octane versions but I didn't notice any difference apart from the price. Having said that, I filled-up again yesterday and added some Castrol Valvemaster Plus that's supposed to increase the octane number.

I've got a single Stromberg: I suppose it might be running a bit lean. I'm getting 30 mpg at the moment so it's certainly running "efficiently"! I set the mixture at idle using a glass spark-plug so I can see the flame-colour in the cylinder. The Stromberg could be running lean at higher revs though.

So, to my plan of action. Triple-S very kindly let me have a couple of old distributors. He described them as "rusty" but a soak in paraffin is getting them clean. I'll either swap-out the part I need for mine, or assemble a complete replacement. That should get the centrifugal timing right. I've already checked the vacuum advance and that seems air-tight.

While that's happening I'm cleaning the air-filter so I've got a level playing-field with the Stromberg.

I'll set the timing at 19 degrees at 1500 rpm. If the Valvemaster has done the trick then there should be no pinking. If not I'll see if richening the mixture slightly solves the problem. If it does then all well and good. If not I'll have to go back to retarding the ignition until the pinking goes away. With any luck I won't need to retard it a full 10 degrees!

I think that sounds like a plan - I'll update this when I've made more progress. In the meantime I've got to go back to the day-job!

Aug 3rd, 2020, 09:18	#6
HRA Junior Member Last Online: Mar 28th, 2024 16:36 Join Date: Aug 2018 Location: Surrey	Thanks Ron-Kwas; that's pretty much how I visualised it. My distributor probably has a slightly different graph since the number ends 077. Looking at the 099 graphs, the heavy spring governs the last 5 degrees of advance. I had to back my timing off by about 10 degrees to stop the pinking (or pinging) so I maybe the change of slope of the 077 graph to starts earlier? Mechanically my work-around seems to be holding-up. I tried to get some photos but the auto-focus on my phone wasn't having it - get close enough to see and all it wants to focus on is the background! However, even though the heavy spring is back in operation I still need to retard the timing nearly 10 degrees to be sure of no pinking. That's set me wondering about the other causes of pinking:[LIST][]Spark plug too hot[]Low-octane fuel[*]mixture too weak I'm running NGKSPARKA007037 plugs - I think they're pretty standard and I haven't seen any of the white deposits and damage that overheating causes. I do usually buy the basic 95 RON unleaded fuel. In the past I did try higher octane versions but I didn't notice any difference apart from the price. Having said that, I filled-up again yesterday and added some Castrol Valvemaster Plus that's supposed to increase the octane number. I've got a single Stromberg: I suppose it might be running a bit lean. I'm getting 30 mpg at the moment so it's certainly running "efficiently"! I set the mixture at idle using a glass spark-plug so I can see the flame-colour in the cylinder. The Stromberg could be running lean at higher revs though. So, to my plan of action. Triple-S very kindly let me have a couple of old distributors. He described them as "rusty" but a soak in paraffin is getting them clean. I'll either swap-out the part I need for mine, or assemble a complete replacement. That should get the centrifugal timing right. I've already checked the vacuum advance and that seems air-tight. While that's happening I'm cleaning the air-filter so I've got a level playing-field with the Stromberg. I'll set the timing at 19 degrees at 1500 rpm. If the Valvemaster has done the trick then there should be no pinking. If not I'll see if richening the mixture slightly solves the problem. If it does then all well and good. If not I'll have to go back to retarding the ignition until the pinking goes away. With any luck I won't need to retard it a full 10 degrees! I think that sounds like a plan - I'll update this when I've made more progress. In the meantime I've got to go back to the day-job!