Dave Jenner Posted March 6, 2014 Share Posted March 6, 2014 Hi all I'm after any help on offer for tuning up a B81 fitted in an Alvis Salamander (RAF Mk.6). I've just finished sorting out the brakes, for the second time, and now need to get the engine running a little sweeter. The only work I've done so far on the engine is to fit new exhaust, a re-placement re-furbished carb and clean the plugs which at the moment are those platinum tipped type, set at 15 thou. I have avoided even thinking about the twin contacts and distributor. I've been told that a good starting point would be to get shot of the plugs and replace with RSN12Y, any suggestions on where to source these at the best price? When she was running last year there was never a 'backfire' so it could be that the points and timing are ok? I have no technical specs on the points and distributor so again, if anyone has any info on these I would welcome the input. At present she starts well on full choke but once it's fully in the engine is sluggish to rev up from idle until about 1500rpm. There is the occasional flat spot and you get the impression that she is not always on all 8 cylinders. I'm hoping this is just a tune up problem and not due to any significant low compression. Any tips, advice and especially any technical jargon on the distributor would be very gratefully appreciated. Cheers Dave Quote Link to comment Share on other sites More sharing options...
Starfire Posted March 6, 2014 Share Posted March 6, 2014 Tuning the B series engines is pretty basic, in that the carburettor does not have many adjustment points. The most likely cause of a flat spot is that the accelerator pump diaphrams have gone and need to be replaced. That is also the case on my Saracen, but I've not yet found a source for them. A lot of the time, ignition problems will look like a tuning issue, especially given the fact that you're dealing with two sets of points. I would strongly recommend fitting an electronic ignition module; Clive has written a very good article about it: http://hmvf.co.uk/pdf/IGNITIONMATTERS.pdf With an engine that has been sitting for a long time, it may be worth doing a compression test. I understand that the B series can be rather prone to sticking exhaust valves. I have a B series engine manual and tuning informaiton for them. If you send me your email address, I can pass them on. Cheers, Terry Quote Link to comment Share on other sites More sharing options...
Richard Farrant Posted March 6, 2014 Share Posted March 6, 2014 (edited) Tuning the B series engines is pretty basic, in that the carburettor does not have many adjustment points. The most likely cause of a flat spot is that the accelerator pump diaphrams have gone and need to be replaced. That is also the case on my Saracen, but I've not yet found a source for them. A lot of the time, ignition problems will look like a tuning issue, especially given the fact that you're dealing with two sets of points. I would strongly recommend fitting an electronic ignition module; Clive has written a very good article about it: http://hmvf.co.uk/pdf/IGNITIONMATTERS.pdf With an engine that has been sitting for a long time, it may be worth doing a compression test. I understand that the B series can be rather prone to sticking exhaust valves. I have a B series engine manual and tuning informaiton for them. If you send me your email address, I can pass them on. Cheers, Terry Terry, The carby does have two mixture screws on it for each venturi. I have had a lot of experience with B range engines and would advise Dave to check both contact sets are clean and adjusted correctly and equally. Also change the condenser. Richard Edited March 6, 2014 by Richard Farrant Quote Link to comment Share on other sites More sharing options...
Dave Jenner Posted March 7, 2014 Author Share Posted March 7, 2014 Tuning the B series engines is pretty basic, in that the carburettor does not have many adjustment points. The most likely cause of a flat spot is that the accelerator pump diaphrams have gone and need to be replaced. That is also the case on my Saracen, but I've not yet found a source for them. A lot of the time, ignition problems will look like a tuning issue, especially given the fact that you're dealing with two sets of points. I would strongly recommend fitting an electronic ignition module; Clive has written a very good article about it: http://hmvf.co.uk/pdf/IGNITIONMATTERS.pdf With an engine that has been sitting for a long time, it may be worth doing a compression test. I understand that the B series can be rather prone to sticking exhaust valves. I have a B series engine manual and tuning informaiton for them. If you send me your email address, I can pass them on. Cheers, Terry Hi Terry, thanks for your reply, will pm you my email as I would appreciate any tuning info that you have. I am aware of the electronic ignition mod, thanks for that info as well which could be something to look at when our funds improve! Regards Dave Quote Link to comment Share on other sites More sharing options...
Dave Jenner Posted March 7, 2014 Author Share Posted March 7, 2014 Terry, The carby does have two mixture screws on it for each venturi. I have had a lot of experience with B range engines and would advise Dave to check both contact sets are clean and adjusted correctly and equally. Also change the condenser. Richard Hi Richard I've found an item on 'Doug's Heavy Metal' on setting up the points using a self made 45 degree quadrant on the rotor spindle and a timing light. Would you advocate this method or an alternative? Alf at the museum has experience setting up these twin point distributors on other vehicles, is the process pretty generic or are there special considerations on the B80/81? Cheers Dave Quote Link to comment Share on other sites More sharing options...
101 Ron Posted March 7, 2014 Share Posted March 7, 2014 Go for the electronic conversion as once set there is no more stuffing around. If you are carefull all wiring for the electronic conversion can be hidden inside the original metal conduit and housings making the conversion undetectable. I used normal BP5ES W8DC N9YC protruded nose sparkplugs as they are self cleaning and cheap. I did away with the ignition lead shielding as it takes much energy from the spark thrown at the plugs. I use the old leads and fittings with electrical shrink wrap to keep things water tight as possible. I now run 25 thou spark gaps with out trouble. I now have a stalwart that doesn't back fire and never needs its plugs out to be cleaned , even if the motor gets a bit fuelled up. It starts first time every time straight away without any choke. Quote Link to comment Share on other sites More sharing options...
101 Ron Posted March 7, 2014 Share Posted March 7, 2014 For high tension lead I used the old fashion copper cored stuff purchased from people who restore old stationary motors. The connectors for the sparkplugs I used NGK brand as they are quality and seal around the sparkplug giving semi water tight qualities. Quote Link to comment Share on other sites More sharing options...
101 Ron Posted March 7, 2014 Share Posted March 7, 2014 Quote Link to comment Share on other sites More sharing options...
101 Ron Posted March 7, 2014 Share Posted March 7, 2014 Quote Link to comment Share on other sites More sharing options...
Dave Jenner Posted March 7, 2014 Author Share Posted March 7, 2014 Go for the electronic conversion as once set there is no more stuffing around.If you are carefull all wiring for the electronic conversion can be hidden inside the original metal conduit and housings making the conversion undetectable. I used normal BP5ES W8DC N9YC protruded nose sparkplugs as they are self cleaning and cheap. I did away with the ignition lead shielding as it takes much energy from the spark thrown at the plugs. I use the old leads and fittings with electrical shrink wrap to keep things water tight as possible. I now run 25 thou spark gaps with out trouble. I now have a stalwart that doesn't back fire and never needs its plugs out to be cleaned , even if the motor gets a bit fuelled up. It starts first time every time straight away without any choke. Thanks for the info, I like the look of your set up and it sounds as if you have had great results. Our vehicle only does short runs, often not getting up to temp so is very prone to suffering dirty plugs so your set up sounds ideal. I've requested a price on the mod from Classicheads. It could work out more cost effective in the long run. Cheers Dave Quote Link to comment Share on other sites More sharing options...
Marmite!! Posted March 7, 2014 Share Posted March 7, 2014 so is very prone to suffering dirty plugs Dump the RSN13P's & fit RSN12Y's they run a lot better on those plugs & are less prone to fouling. Quote Link to comment Share on other sites More sharing options...
lowfat Posted March 7, 2014 Share Posted March 7, 2014 Tuning the B series engines is pretty basic, in that the carburettor does not have many adjustment points. The most likely cause of a flat spot is that the accelerator pump diaphrams have gone and need to be replaced. That is also the case on my Saracen, but I've not yet found a source for them. A lot of the time, ignition problems will look like a tuning issue, especially given the fact that you're dealing with two sets of points. I would strongly recommend fitting an electronic ignition module; Clive has written a very good article about it: http://hmvf.co.uk/pdf/IGNITIONMATTERS.pdf With an engine that has been sitting for a long time, it may be worth doing a compression test. I understand that the B series can be rather prone to sticking exhaust valves. I have a B series engine manual and tuning informaiton for them. If you send me your email address, I can pass them on. Cheers, Terry are these any good http://www.marcusglenn.com/catalog/viewphoto.php?shoph=319&phqu= http://www.marcusglenn.com/catalog/viewphoto.php?shoph=320&phqu=0 Quote Link to comment Share on other sites More sharing options...
marvinthemartian Posted March 8, 2014 Share Posted March 8, 2014 Marcus also stocks the RSN 12 plugs, ref no MG369. Think pump diaphragm is this one http://www.marcusglenn.com/catalog/viewphoto.php?shoph=320&phqu=0, which is ref MG320. The other is for the economy pump, or so my Martian ISPL says. Quote Link to comment Share on other sites More sharing options...
paulob1 Posted March 11, 2014 Share Posted March 11, 2014 I run my stollys on the electronic ignition from jollys and the 13 plugs and have no foulng problems...she runs a treat, I off road one of mine in second and third using the full rev range with great results.. the jolly gear is great... Quote Link to comment Share on other sites More sharing options...
Dave Jenner Posted March 11, 2014 Author Share Posted March 11, 2014 Thanks to all for all the tips and advice; if the vehicle were my own I would give serious thought to the electronic ignition. I've checked prices and it's currently coming in at £260. This is just one of many vehicles at the museum and I'm not going to be able to spend this, at least not just now. It's going to have to be plugs and points for now. Would there be any mileage in removing the plug lead shielding gaining some HT spark, and fitting standard caps and plugs that I could gap at 25 thou? Dave Quote Link to comment Share on other sites More sharing options...
paulob1 Posted March 17, 2014 Share Posted March 17, 2014 would not really help if your points are bad...cheap new dizzys are about for 50 quid and that may be a cheaper quicker option...they usually just bolt in already set up... has anyone ever tried advancing the ignition a tad to allow for the modern fuel, I know the b61 fires at or just past top dead normally but has anyone tried a bit of advance over norm... Quote Link to comment Share on other sites More sharing options...
Dave Jenner Posted March 21, 2014 Author Share Posted March 21, 2014 would not really help if your points are bad...cheap new dizzys are about for 50 quid and that may be a cheaper quicker option...they usually just bolt in already set up... has anyone ever tried advancing the ignition a tad to allow for the modern fuel, I know the b61 fires at or just past top dead normally but has anyone tried a bit of advance over norm... Thanks for this, I have another dizzy to play around with and perhaps fit with new points at a later date. There was also a problem with the carb having muck in it, probably drawn up when I had the petrol tank out to get to the brake cylinder. Running sweet again...for now! Cheers Dave Quote Link to comment Share on other sites More sharing options...
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