Hi
After 33 years of resisting it I converted my ‘64 V8 saloon to negative earth a few weeks back and installed a dynalite. All works well.
The annoying radio interference I hoped would go (I ran it on a polarity converter) is still there although it works better than it did.
New aerial and radio both properly grounded (I think) a new suppressor on the coil (+) terminal to earth and even a capacitor for the alternator (although I suspect it has one built in) make no difference.
It’s a click/crackle which gets worse with engine speed. Any ideas?
Best
Mark
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Probably done to death but radio interference!
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- Classic Wise Man
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- Joined: Wed Sep 05, 2018 9:55 am
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Re: Probably done to death but radio interference!
Hello Mark,
I presume no crackle with the radio on and engine NOT running ??
A crackle that increases with speed is normally dynamo / alternator generated - this will require a suppressor which I believe you have covered.
That said, another overlooked issue is the spark plug leads, modern ones are suppressed (silicone etc) on being manufactured and should be either 7mm or better still 8mm.
Regards.
Richard.
I presume no crackle with the radio on and engine NOT running ??
A crackle that increases with speed is normally dynamo / alternator generated - this will require a suppressor which I believe you have covered.
That said, another overlooked issue is the spark plug leads, modern ones are suppressed (silicone etc) on being manufactured and should be either 7mm or better still 8mm.
Regards.
Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024
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- Extremely Wise Man
- Posts: 1371
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Re: Probably done to death but radio interference!
Mark,
There are two types of radio interference which sound very different.
A clicking noise at tick over, which if you listen carefully coincides with the plugs firing and increases in level but not in frequency with engine revs, is almost certainly ignition interference or noise. Solution is to suppress the ignition both at the coil/distributor and plugs. This can be achieved by adding a .1 mfd capacitor to the distributor 12 volt connection and the + connection on the coil as you have done. As Richard says you need to suppress the plugs, this is best done with modern suppressed plug leads which is the best solution with the V8, it is difficult with the original plug top connectors to fit a suppressor on each plug at that end.
Alternator or dynamo noise is very different, it is more a high pitch whining noise, which increases in frequency and level as engine revs are increased. The alternator you have fitted is already suppressed so I doubt you have a problem there, I would go for the plugs and distributor.
On older cars the heater and windscreen wiper motors can also be a problem but only when they are switch on of course, fit a
.1 mfd capacitor on the 12 volt feed as near to the unit as you can.
As you say the problem which is particularly difficult to sort with the SP250 was done to death on the old forum.
There are two types of radio interference which sound very different.
A clicking noise at tick over, which if you listen carefully coincides with the plugs firing and increases in level but not in frequency with engine revs, is almost certainly ignition interference or noise. Solution is to suppress the ignition both at the coil/distributor and plugs. This can be achieved by adding a .1 mfd capacitor to the distributor 12 volt connection and the + connection on the coil as you have done. As Richard says you need to suppress the plugs, this is best done with modern suppressed plug leads which is the best solution with the V8, it is difficult with the original plug top connectors to fit a suppressor on each plug at that end.
Alternator or dynamo noise is very different, it is more a high pitch whining noise, which increases in frequency and level as engine revs are increased. The alternator you have fitted is already suppressed so I doubt you have a problem there, I would go for the plugs and distributor.
On older cars the heater and windscreen wiper motors can also be a problem but only when they are switch on of course, fit a
.1 mfd capacitor on the 12 volt feed as near to the unit as you can.
As you say the problem which is particularly difficult to sort with the SP250 was done to death on the old forum.
Re: Probably done to death but radio interference!
The aerial should only be earthed at one end preferably the radio end, do not use the aerial as -ve supply, the SP radio suppression with top hat over the distributor with arms to the two plates covering the heads and leads, with all that fitted I never had a problem
Owner since the 70's, Genghis is slightly to my left.
Re: Probably done to death but radio interference!
Thanks you!
Testing spark plug caps seems that they aren’t suppressed. Have ordered 8 supressed one’s. Perhaps that will do the trick?
Mark
Testing spark plug caps seems that they aren’t suppressed. Have ordered 8 supressed one’s. Perhaps that will do the trick?
Mark
Re: Probably done to death but radio interference!
I am aware of shielded spark plug wires bring used on custom motorcycles and cars. Up and up, I actually found a coil of blue in a bin behind a fabrication shop last year and have yet to make up a set for my engine. It is braid wrapped externally the same way as your internet cable without the cover and its available in anodized colors. Just make up a full set of matching custom plug and dizzy shielded wires and bob could be related, in theory. Perhaps this approach along with a coil cover would approximate the star ship Enterprise configuration to reduce the static emissions from the 60's equipment.
Make sure all your grounding points are free of oxidation and corrosion along with braided grounding straps being in good nick
I'll look for the info I had about the shop.
Make sure all your grounding points are free of oxidation and corrosion along with braided grounding straps being in good nick
I'll look for the info I had about the shop.
Bud
Still, that "OTHER" SP 250
https://hosting.photobucket.com/images/ ... &crop=fill
http://i180.photobucket.com/albums/x15/ ... M_0123.jpg
Still, that "OTHER" SP 250
https://hosting.photobucket.com/images/ ... &crop=fill
http://i180.photobucket.com/albums/x15/ ... M_0123.jpg