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Post by dave1800 on Sept 29, 2012 10:15:46 GMT
Hi Chris Yes I had noticed you had managed to make time to get the carb and ignition up so that it runs well at the correct indicated temperature - maybe it was my nagging  I am interested in your comment about the twin carbs being better on a long fast run than running a single carb close to fully open. I guess you are saying that the SUs have a "sweet spot" to use the camera analogy ie a piston lift that provides the optimum economy and performance balance. Do you have any links, I'm fascinated because of my ongoing ignition and mixture control project and don't want to miss something crucial like this. We're never too old to learn! Thanks David Twin carburettors are a sensible choice for this kind of use. A single carburettor will be running close to fully open on a fast long distance run, which is not its most efficient use. A pair of carbs will be running partially open, keeping them more "in the zone" and working efficiently, thus decent fuel economy. David - you may not have noticed, but I have set the engine up again from first principles with decent results. Timing and carburation issues have been dealt with and the temperature has dropped to sensible levels. Chris. |
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Post by Penguin45 on Oct 1, 2012 23:12:04 GMT
I'm looking for the info to justify my comments. In the meantime........  Phwoar! From HI-FLOW. Bring me one back, next time your over David. Chris. |
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Post by indianajones on Oct 1, 2012 23:20:01 GMT
Ohhhhh pretty, and only across the ditch!
-Andrew
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Post by indianajones on Feb 20, 2014 20:07:32 GMT
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Post by Penguin45 on Feb 21, 2014 1:04:28 GMT
You are incorrigible...... (As opposed to cardboard - corrugated.)
The problem we've got here, if you think it through,is the old transverse - vs - inline engine problem. The MGB "B" engine is inline and the manifold is on the right hand side of the engine, sweeping down to the rear. It's actually acknowledged as a very efficient manifold, as far as manufacturers ones go. Now, turn it round through 90° into its correct alignment. The manifold is going to the left (from the front), instead of the right. Somehow, you'd have to bend up a pipe to go across the back of the engine/gearbox assembly, before turning down and back to the rear. Could probably be done, but there isn't a huge amount of room behind the engine, so not quite sure what you'd gain, if anything.
This is where being able to weld would allow you to have so much fun! S/h Peco manifold for instance - it's mild steel and fairly cheap, so no reason that the pipework couldn't be chopped off and turned round into it's correct alignment with some patience and skill.
TBH, the hardest part, if you can do some welding, is the manifold flanges as they're pretty substantial bits of metal. Once you've got them, getting the tube sorted out s pretty simple really.
Chris.
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Post by dave1800 on Feb 21, 2014 2:13:49 GMT
Andrew I admire you enthusiasm and yearning for more power, been there many times! But the first thing to do is to get the engine running properly in standard form before adding any "bolt on" goodies. What I mean is sorting our all ignition, distributor, carb, head, oil consumption, overheating problems and most important brakes. More power will only make these worse and may bring added problems. A well sorted 1800 with 1 carb is nice to drive - I must be getting old . David |
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Post by indianajones on Feb 21, 2014 2:50:13 GMT
lol cheers guys.
The single carb is fine, but I can't help but think a twin carb set up would sound a lot sweeter and give me a bit more pick up.
I fully agree about getting what I have at the moment right and I feel I've made a lot of ground on my beast:
-New radiator cap on the overflow.
-New thermostat with gasket.
-New servo, and I put new pads on her around 2000kms ago, so brakes are pretty sweet.
-Rebuilt the carb.
This is more about idea sharing etc, the above example being great as Chris reminded me that the MGB engine is the wrong way round, so that manifold would need work.
These ideas and mods are more for the engine I'm rebuilding (very....very....slowly lol) .
-Andrew
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Post by dave1800 on Feb 22, 2014 4:27:35 GMT
Back in the real world, sorry, it is a good idea to set yourself a budget and work on the basis that it you may well spend twice that! Then you can work out which are the most cost effective options. You will also need to determine how the car will be driven. There's not much point making it function as a circuit racer but not able to take it downtown. You can spend a few £s or $NZ or many thousands. I would start with trying to locate S or W6/2200 brake calipers to improve the braking. As Chris has pointed out scrap MGBs may be a good starting point for some engine components and you have the links to MGB tuning information already. As far as getting the right carb needle for your air cleaners now the options are to read what others are using on MGBs to get ideas. There is a handy list Google mgaguru.com/mgtech/books/pdf/Tuning_SU_Carburetors.pdf and a look up SU needle selectorThe only way to get it right imho is to use a wideband O2 sensor to see where you are running rich or weak. They cost circa £160 but maybe you could borrow one from a local car club and clip it to the exhaust pipe? Alternatively opt for a slightly richer needle (thinner profile) especially at the wider carb opening, ie full load as your current air cleaner will probably be allowing more air so weakening the mixture which may be a risk. If you are really ambitious you can use a wide band sensor and reprofile (polish) the needle to achieve the right mixture. There's quite a lot on the internet on this. Regards David lol cheers guys. The single carb is fine, but I can't help but think a twin carb set up would sound a lot sweeter and give me a bit more pick up. I fully agree about getting what I have at the moment right and I feel I've made a lot of ground on my beast: -New radiator cap on the overflow. -New thermostat with gasket. -New servo, and I put new pads on her around 2000kms ago, so brakes are pretty sweet. -Rebuilt the carb. This is more about idea sharing etc, the above example being great as Chris reminded me that the MGB engine is the wrong way round, so that manifold would need work. These ideas and mods are more for the engine I'm rebuilding (very....very....slowly lol) . -Andrew |
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Post by dave1800 on Feb 24, 2014 2:20:45 GMT
Andrew It may be worth looking again at the Downton mods (Downton your earlier post) that were available ex factory to give you an idea of how much performance improvements were made and how they were achieved. Mods to the head were made to improve gas flow although you probably wouldn't want to raise the compression too much nowadays with the modern fuel. Another area that was improved was the exhaust flow LCB manifold. Their options were single carb, twin carbs with change of camshaft (unless you had very early Mk1 cam) and special which used an even higher CR head and MGB (1800S profile)camshaft. One thing to watch is the torque range especially if you have lots of hills locally, you will see the single carb version mod is better low down. This engine would accelerate from 10mph in top gear which is handy given the 1800 gearchange. David lol cheers guys. The single carb is fine, but I can't help but think a twin carb set up would sound a lot sweeter and give me a bit more pick up. I fully agree about getting what I have at the moment right and I feel I've made a lot of ground on my beast: -New radiator cap on the overflow. -New thermostat with gasket. -New servo, and I put new pads on her around 2000kms ago, so brakes are pretty sweet. -Rebuilt the carb. This is more about idea sharing etc, the above example being great as Chris reminded me that the MGB engine is the wrong way round, so that manifold would need work. These ideas and mods are more for the engine I'm rebuilding (very....very....slowly lol) . -Andrew |
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