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MG MGB Technical Wrong Distributor for Engine Specs ?? BBS discussion at MG-Cars.info
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MG MGB Technical - Wrong Distributor for Engine Specs ??
| Hi Two years ago I purchased a 71MGBT Engine No 18V E-H13121 Chasis No GHD5-233533G,I viewed the car and duly purchased it,The car came with full reciepts,bills that had ever been spent on the car.On looking through the paperwork I realized the engine was far from standard and was indeed quite heavily modified,These Mods iclude,Bored to 1950cc, Stage3 Cylinder Head,Piper270Cam,Lightened and Balanced Crankshaft,and SU HS6 1/34Carbs.The Car runs quite well, but nothing breath taking,Starts from cold, and really has no major running issues,Plugs are the right colour,Smooth Idle, But does suffer with appalling MPG Figures, I bet it does, your probably thinking. My problem is that I have discovered the distributor fitted is the Lucas 45DM4 with remote AB14 Amplifier. Looking through the BBS archives and other Websites such as Paul Hunts amazing site where Paul states the DM4 Distributor which was fitted to much later cars was really fitted through reasons of economy rather than performance,so I may have the completly wrong curves for my engine specs,Which may be the reason for the really bad fuel economy,and a possible power loss,although I have nothing to compare that with, not having driven other MGs. On the Vacuum Capsule it is stamped 5 8 5 I realize the last digit 5 doubles at crankshaft to 10 degrees,but on Pauls site can not find these vacuum specs for any type of Distributor, So I suspect this disributor may not be the correct one according to my engine specs, I am wondering if there are any other BBS members with the same engine specs,and if so which distributor they have fitted or can recommend. Or for the more knowledgable members, Is this DM4 the wrong Dizzy for these engine specs,What Dizzie can they recommend,or what my next move should be. I know I am going to suffer with not very good MPG figures with these engine specs,But I do think a lot of this is due to the fact that possibly the DM4 is not giving the advance needed and has totally the wrong curves, and has a lot to do with my poor MPG figures. I am not seeking massive power increases,however somebody spent a lot of cash and thought into this engine and It would be nice to know that I am making the very best of these engine Mods. Any advice and help with this,would be gratefully appreciated. Malcolm |
| M Brady |
| You say appalling MPG what figures are you getting? A normal GT should give you 30+ but probably no more the 32 or 33 Before you go spending money, check the usual. Does the vacuum advance work. Do the two halves of the dizzy centre shaft move independantly. What is the timing set at? Take the top plate off and see what number is on the advance plate, this will give the maximum centrifugal advance of the unit, (probably 15). Mechanical advance is a product of the bob weights and, more importantly, the bob weight springs. The two springs should be different weights and slightly different lengths.You say the plugs are the right colour...........what? It would be worth a trip to a rolling road, they can check the timing and advance, and maybe swap the springs,plus the fuel mixture at different loads and speeds and maybe change your needles. After-market cams often require different tappet clearances than those of the OE item. Check with Piper. |
| Allan Reeling |
| Malcolm. Allan often asks good questions and his question about what is your actual mileage is the key to what we are looking at. We need to know what your gas mileage is if we are to understand the nature of the problem, indeed to determine if what you perceive is a problem in your mind also a problem in ours. As to your current distributor, it sounds like you have the later Lucas 45DM4 CEI distributor. The 45 series distributors were designed for better performance (better rotor design, better distributor cap lay out) than the earlier Lucas 25 series. Hence, the basic design of the distributor is not a factor and most of us would consider it to be a useful upgrade. The mechanical and vacuum advance curves are useful to know because you need to know what your current distributor is doing to compare it with published advanced curves. You measure your current distributor's advance curve by empirical testing, either having it tested in a distributor test machine or by using your car's engine as the test machine. Simply start the engine, warm it up, and use a dwell tach (set on the tachometer function) and a dial back type timing light to plot your advance curve. I would recommend taking advance readings every 250 rpm beginning at 1,000 rpm and working upwards until the advance stabilizes and the distributor no longer shows any mechanical advance. Testing your distributor is the only method of determining the actual mechanical advance present and the only system which will allow you to make any valid comparison. Knowing your actual fuel mileage and your actual mechanical advance curve will allow us to help you with some precision. Without such information, only hopeful guesses can be offered. Hopeful guess of my own. Many things, besides the mechanical advance curve of the engine's distributor, have an effect on the car's fuel efficiency. These include the type of tires, the inflation pressures of these tires, the type of rims the tires are mounted on, the alignment of the front wheels, and all components of the braking system. All of these area can have an effect on the fuel efficiency with dragging brakes significantly lowering fuel efficiency. Do not focus on a single area in your research, especially one which you have not taken the opportunity to test or have tested. Your distributor could have been installed as a rebuilt unit, offered up by someone highly competent and knowledgeable about MG engine requirements, or it could be a salvage yard unit. Until you test it, you do not know and neither can we. Les |
| Les Bengtson |
| On this side of the Pond, there is a gentleman named Jeff Schlemmer who custom tunes distributors to your engine's specifications. You tell him what components make up your engine, the type of driving that you intend to do and he sets up your old distributor so that it is a perfect match to your engine. All of the B owners I have heard from rave about the results of his work. He has access to parts that have been long discontinued. If you like, he will build you a distributor from scratch and his prices are very reasonable. RAY |
| rjm RAY |
| Malcolm, As Allan comments, what do you consider appalling may not be... Let us know. Also as others have commented, setting up your engine, dissy and carb's would best be done on a rolling road. However he's a few things to consider:- The piper cam is a mild road one which could be smooth at idle. The HS6's will only really take effect in the mid to high rpm when the air demand is required and this assumes they have had the needles correctly set! It's not entirly impossible thay will cause problems at idle with a stage 3 head which I'm assuming has larger valves and the ports opened up. Again this head will work best at higher RPM with the possibility of "slow air flow" at low rpm. An effect of slow air flow can be a loss of fuel atomisation at the carb or the inability to keep the fuel suspended in the air until it reaches the cyl. Both of which will affect the engines ability to produce power (and torque) low down in the range. But there again with 1950cc's sucking the air in this shouldn't be a problem (provided the next comment is true)... Also, I'm assuming you have a good quality sports exhaust fitted? If not, most of the work on improving breathing on the inlet side will be largely wasted!! And all this before you go anywhere near the advance curve! A decent plug and play dissy is the Aldon or 123 which comes with a number of preset curves covering a number of std performance configurations. However these will always be a compromise (just quite good ones) on a full RR set-up. Good luck and let all know how you get on.. MGmike |
| M McAndrew |
| Malcolm Check out the attached which give a good easy to understand (I thought so anyway) overview of how the dissy advance works. http://www.teglerizer.com/mgstuff/lucastuning.pdf MGmike |
| M McAndrew |
| All good advice and relevant questions above. As I have said before, my car with 1950cc overbore stage II head fat road cam etc etc goes very well and can return over 40 MPG (UK gallon). It has the ST spoiler fitted which will help. It only getsthis at an indicated 65 on free flowing motorways, around the lanes on an event it gets 25 driven safely but briskly. The engine is doing a lot of work here through the gears and when its not its off the cam and not breathing well. Do you know what the static timing is. I set mine to 10 using the crankshaft marks and then advanced it till it started pinking and then backed off a bit. This also lets you check the vuacumn retard which is vital for economy. While the car is going up hill at a moderate throttle opening and starts to ping you can open the throttle without changing down. The pinking should stop as the capsule relaxes. |
| Stan Best |
| Hi Thanks to all for all your comments, Allan & Les, I will do a Dizzy Curve Plot,and do an accurate MPG test,I will also remove dizzy and check out what is stamped on the advance plate,and check general condition, Spark plug colour is Light Brown, According to Piper Tappet clearance is Inlet 14"Thou Exhaust 16"Thou set Cold,which I did last Autumn/Fall, When I give a hefty suck on the vacuum tube to dizzy, the plate does move, The 45DM4 is CEI and is the factories pointless system,which is supposed to be a good reliable system,but my original question is because it is a much later system its design was buyest toward ecconomy and not performance, How ever I hear what you guys are saying and can not really help until I give you the information required, Which I will give you,Just give me a couple of days,Yes a trip on the rolling road would be great,However I live in the Highlands of Scotland and such places are few,and thought I would try and get some general opinions,before making such a costly trip. Tyre pressures and brakes checked out O.K. Ray, I have heard of Jeff Schlemmer but think this would be a bit unecconomical on this side of the pond, MGMike Tubular stainless Manifold/Headers Fitted and Big Bore Exhaust fitted,If I find out this dizzy is not suitable I probably would go for the Aldon or the 123 but lets see if I can get to the bottom of this problem first,I will change Dizzy if this DM4 is found not suitable or unservicable,Thanks for the link to Teglerizer a very imformative site. Stan,I know the Timing is set to a lot more than 10 degrees,The car will ping if I drive at very low speeds in to high a gear,but that is no major problem I will set about the work and come back with some figures, soon. Thanks to All Malcolm |
| M Brady |
| After doing many engine modifications and installing a supercharger, I found the most difficult part in getting everything working together was the ignition system. There are few companies that cater to the special needs of performance B series engines, 123 and Mallory being the exceptions. I located an HEI based distributor, similar to yours in design and function, in the Southern US. It is made by a company called Davis Unified Ignitions. They use a distributor from a '80 Jeep 4 cylinder engine and modify it to fit the B cam drive. They make all of their own components including a coil, that's built into the distributor cap, that puts out 50,000 volts. They also make their own modules that increases the dwell time and allows you to open the plug gap to .055". They will set it up to whatever specifications that you provide them with. I've been running one for 8 years and it is really an incredible unit. RAY |
| rjm RAY |
| The first thing to be aware of is that the electronic distributor was never fitted to UK cars by the factory, only those to American spec. Having said that there is no reason that such a distributor cannot have the correct curve for your engine, as that is down to the mechanical centrifugal and vacuum advance mechanisms and not the electronics, which are little more than a transistor switch replacing the points. The reason that America got the electronic distributors is that they were required to run for 50,000 miles without adjustment and stay within MPG limits. I've run points for 15k with little problems, but 50k would be something else. With a modified engine the only way you are going to get the correct curve is by putting it on a rolling road, or buying an engine and distributor package that the supplier has already put on a rolling road. What MPG you are actually getting is the key question. I've got low 40s out of my roadster long-distance touring in France, and 34 out of my V8. However if I use a V8 tank knocking around locally it can be as low as 12. But at the end of the day journey for journey and car for car the driver makes the biggest difference. The ignition system isn't going to make that much difference as long as it works well enough to fire each cylinder when it should. Electronic trigger, dual point, high-voltage and large gaps are only tinkering at the edges and are worth more in bar-room bragging points than MPG. |
| PaulH Solihull |
| Paul, you are absolutely right at the end of the day these are dated engines, the ignition is not computerised, as long as it is firing at the right time, the driver is the biggest factor in economy. I am still amazed how economical,( relatively speaking,) the modern V8's are, compared to the old gas guzzlers of the late 60's early 70's. So if my GT uses a little more fuel, never mind, it's fun to tinker for performance rather than economy, for me! Mike |
| J.M. Doust |
| Hi Gentlemen, Sorry for the delay in getting back oweing to the snow here in the Highlands, I can now supply the information,most people were asking regarding the low MPG figures I am encountering and as to the DM4 Dizzy being correct for the Engine specs I have in my 71 MGBGT, First of all I did the Dizzy plot, the results were Timing was checked at 600RPM vacuum disconected & plugged =16 degrees for the rest of the test I reconected the vacuum to dizzy, at 800rpm =16deg 1,000rpm =18deg 1,500rpm =20deg 2,000rpm =26deg 2,500rpm =28deg 3,000rpm =30deg 3,500rpm =32deg, There was no further advance than 32degrees at any higher RPM. The next step was to remove dizzy to do some visual checks inside,and to find out the numbers stamped on the Advance plate removing the dizzy proved diffucult as the dizzy was seized/frozen to the engine block, When dizzy was removed,apart from the Lucas logo and the the letters DM4 somebody had erazed all other numbers which probably denoted centrifugal advance on the outside of the Dizzy. once stripped the inside looked fairly clean with no signs of corrosion,I noticed the advance plate and find that the number had also been ground away, the only number I could make out was the number 1, the area had been quite severely ground away, Maybe to allow the fitting of larger advance springs,( only a guess) There was no wear in the shaft or bearings,I just cleaned all the old grease off which had solidified over time,and used light weight oil,and made sure every thing moved easily, I then replaced the dizzy and timed the engine at 15degrees at 700rpm, I also opened up the Plug gaps to 30 thou, The engine started easily and seemed to run well, The snow had melted so I took her out for a good run, Well what a differance she ran really well, responsive, smooth, she ran like a little sowing machine, I can,t fault the running of the car,and the service I did on the dizzy was well worth it. While I was out on this drive I did the MPG test that most people had asked about, I emptied all the fuel out of the Tank,then filled it with exactly (4.5 Litres 1 Imp Gal)of Fuel,Travelled at 55mph on level A Road no hills, And she ran out of fuel 19 miles away from home, So MPG figure is( 19 miles per gallon IMP gallon) So to my way of thinking pretty poor MPG figures,Do you think there is a problem somewhere,or is this a normal figure for a car with the engine specs, which I gave in my first Post. A big thank you to all,who have taken part in this Thread. Malc |
| M Brady |
| The DM4 distributor was standard on the MGA while the MGB used the Lucas 25D4 distributor. It would seem that you have a rebuilt MGA distributor in your car and that will need to be taken into account when you purchase tune up parts. The mechanical advance curve is not labeled on the outside of the distributor. The specification number is and was probably removed when the distributor was rebuilt to its current specification. That may, also, be reflected on the grinding away of the cam stop. Your 1971 MGB should have had either an 18V581 or 18V582 engine depending on whether you have overdrive or not. The distributor for that engine was the Lucas 25D4 to specification number 41288. The static advance was 10 deg BTDC and the initial stroboscopic timing was 13 deg BTDC at 600 rpm. The mechanical advance curve was: 0-6 deg at 600 rpm 4-9 deg at 700 rpm 7-11 deg at 900 rpm 13-17 deg at 1600 rpm 18-22 deg at 2200 rpm You would add in the static timing to the numbers shown for the distributor advance to get your total timing taken with a timing light at the crankshaft. It would seem that the overall advance is within the ball park for your engine, but it seems to be coming in somewhat later than the factory specification. This might have an effect on your fuel economy, but I do not see that this alone would drop your fuel economy down to what you are reporting. I would suggest that you drop Peter Burgess an e-mail and ask him his recommendations for the best advance curve for your distributor. I would, also, check out things like front end alignment, dragging brakes, and any leakage from the fuel system. My cars are getting in the mid 20 mpg range with US gallons and spirited driving. Yours should be, at least, in the mid to high 20s even if you do not have/are not using the overdrive. Les |
| Les Bengtson |
| Les, In Malcolm's original post, he described the distributor as a 45DM4, not just DM4. I don't know which he meant or if that would change your pegging it as an MGA distributor. Malcolm, When you emptied the tank, how did you empty it? Did you do it with the electric pump up by the carbs? If so, your mpg test should be valid. But, if you emptied it entirely, there is usually some remaining fuel that the pump doesn't pick up and that would skew your results. I certainly agree that 19 mpg is appalling. One possible suspect for the poor mileage is the 1-3/4 inch carbs. I have been led to believe that they would only be an improvement to performance at high engine RPMs, and that they would add little (or maybe detract from performance) at RPMs that do not exceed the cfm abilities of the original 1-1/2 carbs. It may also be that something unfavorable happened with the manifold that was used to convert it to the 1-3/4 inch carbs. Charley |
| C R Huff |
| Les, Sorry for misleading you, My Mistake As Charley says the said Dizzy is indeed the 45DM4 CEI type, and is NOT the DM4. Charley: I did indeed empty the fuel tank with the pump at the Carbs, I,m glad you agree about the crap mileage. Many Thanks Malc |
| M Brady |
| Charlie. You are perfectly correct. The MGA distributor is a DM2 and I spaced it when reading DM4 which, as Malc notes is a 45DM4. To the best of my knowledge, the UK MGBs continued to use the Lucas 45D4 distributor until the end of production. Thus, finding a 45DM4 would tend to indicate that someone has replaced the original Lucas 25D4 which came with the car. Probably considered to be an upgrade in the same fashion that people install various points replacement sets into the older points type dizzies. With a little tweaking, perhaps none, it should function well, especially after the annual maintenance has been done, as it has here. Again, Peter Burgess would be the best person to contact, in the UK, about the best mechanical advance curve and vacuum advance to use with an engine modified for higher performance. But, it is well to remember that even minor things, such as tire pressure, can have an influence on fuel economy. Dragging brakes can significantly reduce economy and even such small losses, such as could be due to wheel bearings either going out or needing to be inspected and repacked with grease can, collectively, take away from fuel efficiency. Peter should also be able to give a rough estimate as to whether the performance upgrades will take away from average fuel economy. Like Charlie, the HS-6 carbs caught my eye and I wonder what, if anything, would be gained or lost by switching to HS-4 carbs. Again, something Peter can answer, hopefully here so we may all learn. Les |
| Les Bengtson |
| Hi Les, I dont know about teaching anything new, I hope I never stop learning :) Hi Malc To be honest it sounds like your dizzy is tired and the light spring is advancing too early with the figures you give. Why the figures are as they are is irrelevant. As Les has said it needs to suit your car. It needs sorting on a rolling road even if you have to go away and buy another dizzy. The engine specs you have are pretty vague. What is a stage 3 head? What CR, who did the head? If the head is pretty 'hairy' and you have big carbs the cam is too mild to use the potential and will waste gas velocities and fuel economy at low rpms. 1950s are less economical than 1870s, the bore size is great for racing as you get a bigger engine. The combustion process is better with a smaller bore. 32 seems a lot of top end advance for what should be a hairy engine. Peter |
| P Burgess |
| Well at least its going fairly well in return for the fuel! The 19 mpg figure is subject to a lot of experimental error the way you have done it. Its usual to brim the tank and note the mileage, run off that fill to the point where you refill, say about 1/4 and again brim and note the mileage. This will give you miles and fuel consumed for that tank and if you continue this for several tank fulls you will get a very accurate overall figue plus a general idea of how different use affects the consumption, eg did most of one tank get burned on motorway running (here you car should pretty well. I would expect about 25 mpg with your race orientated set up. This is based on a car owned by someone else here with a similar set up, an ex Slades Garage car. A pair of standard SUs and a trip to Peters rolling road when the weather is better might get that up to 30. You divide miles by litres gives MPL and then times 4.5 for MPG. |
| Stan Best |
| Hi All In responce to Peters Thread, Looking in the Moss Catalogue, Quote: Stage 3 Head: These heads are for tuned engines Requiring flow capacity to match the relevent camshaft and carburation modifications.Recommended for all fast road engines,The inlet valve size is increased along with the ports and chambers to produce the special flow profile, All heads are supplied with new valves, road uprated valve springs and new valve springs. You wanted to know who did the engine mods, I,m looking at a bill here from 1990 From ALDON AUTOMOIVE HARTLEBURY, WORCESTERSHIRE,ENGLAND, 1 Regrind Crankshaft .010" Mains & Big Ends 2 Grit blast flywheel,Lighten on rear & skim clutch face. 3 Balance crank, front pulley,flywheel & clutch cover. 4 Check conrod big end diameters.(all + 1/2 thou over max diameter.replace cap joint faces & rehone rods to correct size. 5 Lighten and balance rods. 6 Rebuild rocker assembly including new rockershaft. 7 Remove steel sleeve from rear of crank & supply & fit new bronze spigot bearing. PIPER 270 Camshaft = £27.20 Stage 3 Cylinder Head £255.00. The Rebore and Engine rebuild was done by another company. The Lucas 45DM4 was purchased from the MG Owners club in 1990,but do not have any records regarding any mods to this dizzy,but can say that it has been modified because of the erazing of most of the numbers on the dizzy. So there you have it Car running well but a real juice guzzler, The car is 4 syncro with O/Dr. I do not normally drive at high revs,and have not driven the car over 70mph, I could not afford it! It sounds the only way forward is to get it on a rolling road, and see what is going on. Many Thanks to all, Malc |
| M Brady |
| Hi Malc Are you saying you have a Moss stage 3 head? I cannot quite understand you. You mention Moss, then Aldon then someone else doing the machining? There are no set specs for what a modified head is or how much bhp you can expect. That is why I ask who did the head. Sadly not like measuring the pitch on a bolt thread. What sort of compression readings are you getting? Peter |
| P Burgess |
| Hi Peter, Aldon Automotive,did the work on the engine as of my last thread, built and supplied the head to stage 3, I only included the paragraph from the Moss catalogue,because you asked what a stage 3 head was, according to bills,receipts,etc For some reason the Rebore was done by another company,who then did the engine assembly I don,t know why? I,m sorry if I confused you,as all of this had had been done by P/O I,m confused myself! I have not done compression checks, I don,t have compression tester to check this at present. Many thanks for your responce and to others who have responded. Malc |
| M Brady |
| Hi Malc Aldon did really fine heads, their stage 3 featured 1.69" inlet valves and 1.44" ex valves. Moss stage 3 (which we usually do features the 1.69" inlet valves and 1.34" ex valves). Aldon usually aim for 9.5:1 CR, we would usually aim for 9.75-10:1. Checking the compression readings would give an idea as to what CR you are running. Peter |
| P Burgess |
| You indicate the advance was the same with vacuum disconnected at 600rpm as connected at 800rpm. Was the throttle open a bit more to get the higher rpm? Or did simply reconnecting the vacuum cause the revs to go up? Where is your vacuum source, carb or inlet manifold? Vacuum advance has a significant effect on cruising economy, your ball-park 19mpg at 55mph is dire. |
| PaulH Solihull |
| Hi Paul & Others, Paul, The increase in RPM was due to my adjustment of the throttle cable adjustment, ie: Bespoke HS6 Carbs Throttle bracket, There was no increase in RPM 600rpm - 800rpm from vacuum or centrifugal, I,m sure there must be something wrong somewhere,for the car to give me this 19MPG, no smell of fuel,the car does not smoke in any way, May be a Head problem?? The next time I go out I will connect containers to float bowls, Just in case. Malc |
| M Brady |
| Malc, I'm now seriously hooked on your problem! I feel a road trip coming on... How far in to the Highlands are you? I'll bring a compression tester and a colourtune to have a quick look in to the cyl's. The dissy might not be optimal but I don't think it accounts for such a shortfall. Has it always been this bad or has it got worse since you bought the car? Just a wild sideways thought! Is the gearbox and diff standard? One way to explain a serious reduction in MPG with an engine which seems to be running well is to run with a much higher diff ratio eg for hill climbing. What sort of engine speed are you doing at 70 with/without O/D (or what speed are you doing at say 3k rpm)? MGmike |
| M McAndrew |
| Hi MGmike,and all You would be most welcome ! I live on the A9 East Coast a small town HELMSDALE which is approx 60 miles north of INVERNESS KW86HH. Fuel consumption has always been like this,since I bought the car. As far as I know Diff is standrd GT. I,m not sure about RPM at 70mph, or Engine speed at 3,000rpm, But O/Dr is working with no problems. I will get back to you with these Questions. I was looking at the John Twist W/site( video 29) SU H type Carbs with regards to the Dustless Suction chamber tops, either with or without holes in the cap, I have noticed that my suction chamber caps are without holes, and the suction chambers also are without holes,according to the video this should not be, one or the other should have this hole,( Cap or Chamber) unless this is not the case with HS6.? But I can,t see that they should be any different ? Can any one shed any light on this! Many Thanks. Malc |
| M Brady |
| Malc, that would be an interesting road trip! It's not surprising you can't get to a RR. I'll never say never but Inverness is a long way north for me.... There again I've always wanted to be up your way for the longest day and play golf at midnight! who knows, maybe this year! I'll check my spare set of HS6's for a comparison and let you know but one of them will need a hole. Without one the car will run rich. Basically, as the piston moves up it will need to allow the air above the dashpot oil to go somewhere. If not, the area above the dashpot oil effectively becomes pressurised and prevents the piston moving to the extent needed. This in turn causes the carb's main airflow to pass the jet at a higher speed than it needs to and thus draws more petrol. Now you would expect the plugs to show some sign of running rich, but... If it only runs rich during acceleration (when it should) and at "high speed running" returning to normal at tick over, it's just possible the plugs are cleaning themselves before you check them! So, get some new damper caps. The nice brass ones with MG logo's look good, but drill a 1mm hole as a short term test. Or get to a RR to confirm! MGmike |
| M McAndrew |
| Hi MGmike,and all, Mike: If ever you fancy a short break up here,car problems or not,We do have a spare bedroom and you will be most welcome,I would not expect you to come all that way for one day, As I say if you fancy a short break up here, You know where you can now stay. Just may be, this could be the problem then ? I will take off the Dashpots and just make sure there is no breather hole in them, As I have stated before, plugs are a tan colour,which I took as mixture OK,Car does not smoke,But Tail pipe is always sooty,at the end which I could not understand, I will check dashpots for breather holes, and confirm. I did order Two caps once from Moss but they were too small for my Dashpots,I think they are in the drawer somewhere. Dornoch and Brora Golf Clubs are both local,with some good and empty roads up here. Malc |
| M Brady |
| Hi Malc are you running leadfree? Peter |
| P Burgess |
| Hi Peter, Yes I am! MGmike (I can confirm There are no breather holes in Dashpots or caps) |
| M Brady |
| You will always get black on end of ex pipe with leadfree. You need to look for 'thick' black too rich....thin black just right. It may be worth investing in an innovate AFR meter so you can set the car up yourself. Your dizzy curve is 'near enough' to not run too bad. Peter |
| P Burgess |
| Hi Peter & all I drilled the 1mm hole in the dashpot caps, And took the car out for a short ride, The Car seems much more responsive and much livelier, In my first post I did describe the peformance as, Nothing Breathtaking, The performance now is excellent,very reponsive no complaints, However I would like to try the AFR Meter Test as of your suggestion and that will be hopfully all that is needed for the coming Summer, I can not report on fuel consumption as yet,but I think I am getting close to a result. Peter can you suggest an affordable AFR Meter for the Home Machanic, ( Or Me!!!) Many Thanks Malc |
| M Brady |
| Hi Malc This is a link to the one we have on our rolling road http://www.turbomatrix.co.uk/product_info.php?pName=ngk-powerdex-afx-airfuel-ratio-monitor-kit-19563-2 We also use an innovate stand alone one http://www.grahamgoode.com/innovate/new/inn3806.html I notice some cheaper ones on ebay but I do not know the quality as I have not used them. Peter |
| P Burgess |
| If you are good with a soldering iron you could try www.14point7.com He it in Canada but his prices are USD. I often consider treating myself to one but end up spending my pocket money on something else. |
| David Witham |
| Hi Malc...just had a thought whilst posting on the Weber thread....you can check the effects of too weak by pulling the choke on a little and see how the car responds, you could always buy a pair of 'stair rod' shaped needles and file the profiles step-by-step, howzat for cost effective tuning? If you have a friendly garage with a CO meter holding the revs at say 3000rpm gives a similar reading to cruise conditions, maybe a good starting point? Peter |
| P Burgess |
| Hi Peter, Thanks for returning back to this thread, As well as owning the old and beloved MGBGT, I own a Ford Focus Estate,So going back to when I did the MPG Test,of which I reported 19MPG I did this in the following manner,Drained Tank to empty and Refilled with 1 Gallon, Drove South on A9 at 50-55mph till car ground to a halt, I was quite lucky being able to pull off the Road and parked in a layby and then refilled the tank,recording the mileage that the Gallons worth of fuel had got me. Today I had to go somewhere,which took me past the same Layby, I have been thinking about this for a bit now, So I zerowed my Trip Meter in the Focus before I left home, Same route, when I got to the Layby I looked at the Tripmeter in the Focus and it read 23 Miles. I know this still, isn,t a very good mileage figure,but it is better than 19 mpg. Your Thread Peter,(I seem to have lost you a little) Why should I want to check the effects of a weak mixture on a car that is giving bad MPG figures, surely the car if anything would be running over rich, However according to plugs mixture is fine I am currantly working on the engines breathing, and when finished will have to of course retune the Carbs, at the same time I will look at the needles and see what they are, Then judge from engine performance and MPG figures if any needle changes are required, At the end of the Month the MOT is due so that will be a good time for me to get a CO reading done, What sort of CO figure should I be looking For ?? Obviously the Tripmeter on the MG is not reading accurate and or possibly the Speedo. ( With Greatest Respects) Malc |
| M Brady |
| Hiya Too weak can mean you have to use too much throttle and run inefficiently.I was also trying to say you can get it to run weak then increase fuel to suit. Try for say 3% at idle and 3% at 3000rpm steady throttle. You could also try taking the oil from the dashpots and snap accelerating below 3000 rpm, if it doesnt hiccup it is way too rich. What needles are you using at the moment? Peter |
| P Burgess |
| Without reading all of the above. Have you looked at some more obvious stuff, all of which affects MPG. Wheel and tyre size, circumference of standard set up is 77/78" Tyre pressures. Tracking. Check brakes for binding. Engine over-cooled. Too high a tick over. Clutch slip. Flooding carb. That'll have to do, food is calling. |
| Allan Reeling |
| Malcolm, Could I suggest the best way to estimate MPG is to do it on tank fill/miles covered, recorded over a reasonable time-period, such as two to three months of driving. That way you 'average' out the more fuel costly startup/warmup periods and the shorter/longer runs that actually construct a more realistic overall MPG performance. The method also allows for influence of more/less dense traffic situations and topography driven. A single gallon of fuel speaks only of the context in which it was consumed. Allowing there are comments above from people much more adept at this stuff than I. Regards Roger |
| Roger T |
| Many Thanks to all that have contributed to this Thread. And I have learnt a lot from many people,From Professional Engine Builders, to weekend mechanics,like myself and from people from all around the world with the same common interests MGBs. I first started this thread under the Heading, Wrong Distributor for Engine Specs, I now know the distributor that I have fitted Lucas 45DM4 CEI Ignition is not really a problem, with my engine setup,I now know it,s not the actual distributor,But the components within,a Distributor that does make the differance. The cars performance is very good,it,s just the crap MPG figures that the car is presently returning,which tells me something is amiss, maybe a set up problem somewhere So I Feel this Tread has somewhat deviated from the original Question posted, My only problem is the MPG,consumption, I will be Stripping Carbs,Set them up,amongst doing other work,I will work out MPG figures on full Tanks over the Summer, I will post the results of my investigations as of and when the problem is solved, When this issue is solved I will start a new Thread, High Fuel Consumption Solved, I just think the current thread has now deviated somewhat,and the Low MPG should really be covered under a new Thread. Many Many Thanks to all. Have a great and Safe Summer. Malc |
| M Brady |
This thread was discussed between 07/03/2011 and 03/04/2011
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