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PV, 120 (Amazon), 1800 General Forum for the Volvo PV, 120 and 1800 cars

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544 B20B help

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Old Jul 22nd, 2021, 04:08   #11
blueosprey90
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The MG engine is fairly similar to the Volvo. Here is a link to the potential causes of dieseling in our MG engines. Please note that the combustion chamber is in the head, not the block.

https://mgaguru.com/mgtech/engine/ro101.htm


By running with the vacuum disconnected, you are getting no vacuum advance from the distributor, only mechanical advance. Consequently you are probably running too retarded. This will contribute to overheating and perhaps your other issues.
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Old Jul 22nd, 2021, 07:34   #12
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[QUOTE=lelshaddai;2755553]This is the distributor I have. I know it is not correct but I cannot find the correct one. This one has worked for many years.

It is pretty clear now that the first move is to get the correct distributor and get it timed correctly ...
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Old Jul 22nd, 2021, 08:59   #13
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Perhaps this the time to bite the bullet and get a 123.
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Old Jul 22nd, 2021, 09:12   #14
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Quote:
Originally Posted by arcturus View Post
Perhaps this the time to bite the bullet and get a 123.
The most reliable will always be the original with points 👍
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Old Jul 22nd, 2021, 09:30   #15
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Quote:
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The most reliable will always be the original with points 👍
The 123 is a lovely bit of kit especially as original ones are getting worn and harder to source. They don't do anything different to a original in proper working condition in the sense they have the same ignition curves but there is less maintenance. If you want to keep original totally fine but I can't see any reason why not to fit one.
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Old Jul 22nd, 2021, 10:30   #16
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Originally Posted by lelshaddai View Post
This is the distributor I have. I know it is not correct but I cannot find the correct one. This one has worked for many years. Also pic of cylinder inside.


Understand you have taken the distributor apart to take pictures, i.e. cap and rota - but have you removed the screw that holds the points in place ? or is it missing ? that won't help :-(
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Old Jul 22nd, 2021, 10:40   #17
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Distributors.
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File Type: jpg Volvo Distributors.jpg (179.1 KB, 7 views)
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Old Jul 22nd, 2021, 10:57   #18
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Quote:
Originally Posted by Burdekin View Post
The 123 is a lovely bit of kit especially as original ones are getting worn and harder to source. They don't do anything different to a original in proper working condition in the sense they have the same ignition curves but there is less maintenance. If you want to keep original totally fine but I can't see any reason why not to fit one.
All aftermarket electronic ignition units will fail sooner or later in my 50 year driving experiences ... They don't really give anything noticeably better , and you are stuck , you will never get it going ...... with points you will get on your way with a screwdriver . the more simple the better .👍
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Old Jul 22nd, 2021, 11:18   #19
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Quote:
Originally Posted by Clan View Post
All aftermarket electronic ignition units will fail sooner or later in my 50 year driving experiences ... They don't really give anything noticeably better , and you are stuck , you will never get it going ...... with points you will get on your way with a screwdriver . the more simple the better .👍
That's if it is in proper good condition to start with after 50 to 60 years. The 123 are a pretty reliable bit of kit and my thinking is it's one less thing to go wrong on a ageing car, there's always stuff that needs doing if running them daily. If you have a dizzy in good condition and you're happy to maintain it then no need to change, if like in this instance it isn't and not correct a 123 is a good choice. But if he wants to source a original one, recondition it and maintain it then it will obviously work and be reliable as well. For me there's no valid argument against either option.
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Old Jul 22nd, 2021, 15:22   #20
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The distributor appears to be from a late B20 from the last of the 140s or the earliest 240 before they received the OHC engine. It doesn't even show up on that list posted by Derek. I thought all the B20s in the final 140s and the 240s in the US were K jet starting in 1974 or 1975. However, carb equipped 140s and 240s did continue on in Canada well into the '70s so perhaps it came from a Canadian spec B20.

I think the designation means that the distributor is equipped with vacuum advance whereas the typical B20B engines would be equipped with vacuum retard. The typical distributor on a B20B pre 1974 would be a JFUR4. I don't have any data on the later distributors. It might be equipped with very little centrifugal advance which may be the cause of your lack of advance or the advance mechanism could be stuck. Pull the points plate off and see if the centrifugal advance operates smoothly. If it does, then you may have to dig up the specs for a late B20A or B (perhaps Canadian spec) to find out what the specified advance is. The advance curve may be wrong for your particular B20B depending on whether you have a high or low compression B20B. If so, you may have to investigate replacing the advance mechanism.

As an observation, if the distributor has not been rebuilt then it probably has shaft wear which causes timing problems at higher RPM. The distributor on my 1971 B20E worked fine at low RPM; but, as you increased the RPM you could see the timing marks bouncing around quite a bit starting around 2500 - 3000 RPM. A new 123 distributor might be one way to address your distributor uncertainty and eliminate any wear issues.

The top of the piston looks moderately clean. The bigger problem would be the actual combustion chamber. In particular are there deposits on the exhaust valve which runs hot and provides more opportunity for hot ignition sources? Since the engine appears to be out of the car I would assume that you are going to do an engine clean which may address most of the run-on problems.

Last edited by 142 Guy; Jul 22nd, 2021 at 15:32.
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