Ernest Posted May 22, 2015 Report Share Posted May 22, 2015 HI all I think that my query is a little 'messy' in that the solution to it might be quite complicated.....well I thought I would and least ask!! I bought a 4A about 4 weeks ago from a reputable TR spare/repairs/sales co. They said that the carbs were new. I have done about 300 miles I the car now and although quite pleased overall I am sure that it isn't running as it should. When accelerating all well but as soon as I lift off the accelerator (even just slightly) it runs quite 'lumpy'. There is an amount of light blue smoke when accelerating from standstill (oil pressure good) and the inside of exhaust tube is very dark, as are plugs, and tick-over is a lumpy 1100/1200, so I suspect it's running 'rich'. I took it to a reputable TR garage and they 'balanced' the air in-take between carbs, plus made a couple of adjustment to accelerator/choke but if anything this made the running slightly worse. I am thinking this issue might not be carbs. but am at a loss where to start. I live Bromley, south London and I don't know of any garage locally that I would have confidence in for a full tune-up. So, two questions: - Any ideas on what might be the problem.....plus any possible solutions? - Does anyone know of a reliable garage/mechanic in south London or Kent that they have confidence in? What do you think? Ernest Quote Link to post Share on other sites
RogerH Posted May 22, 2015 Report Share Posted May 22, 2015 (edited) Hi Ernest, is there oil in the carb dash pots - if not it can cause chaos. Why not contact the Kent GL and ask for garage recommendations locally. have you spoken to the garage that sold the car - they have some responsibility. Roger PS - I assume they are SU carbs Edited May 22, 2015 by RogerH Quote Link to post Share on other sites
Peter Cobbold Posted May 22, 2015 Report Share Posted May 22, 2015 (edited) Hi Ernest, Well..... thats two TR garages I would not regard as 'reputable'. If they cant fettle SUs then what else are they rubbish at. But we'll assume they done their best with the jet adjustment ( lean-rich) and butterflies. The seller should be sorting this for you, as Roger says. Try a little oil in the dashpots as Roger says, bur assuming that ake no diiference then: Blue smoke is oil burning, black smoke is from unburned petrol ( way too rich). But if its a freshly rebuild engine the rings may still be bedding in. New SUs might not have the right spec for the TR. Any documents to help? - seller should know. You can check the spring by lifting one of the domes. There should be paint on them that tells you the rate. Check against pukka TR4 carbs ( ask here ) When lifitng the dome lift it straight up so you dont bend the needle.!! and watch out for the piston falling out !!!! Use a micrometer to check the needle is correct for the engine. With the dome off you can see the level of the fuel in the jet, it should not be at the top but several mm lower. If its overlfowing then that could be the problem - reset the fuel level in the float chamber. Hopefully the fuel pressure is not too high. Or ask the seller to do all the above until the mixture is right. Peter Edited May 22, 2015 by Peter Cobbold Quote Link to post Share on other sites
trevor Posted May 22, 2015 Report Share Posted May 22, 2015 Hi Eanest, Good to meet you at Kent meet weds. I have heard good things about Sanspeed in Bexleyheath , 020 8301 4676 Good luck, Trevor Quote Link to post Share on other sites
Steve Priest Posted May 22, 2015 Report Share Posted May 22, 2015 It you can't find a good garage then perhaps arm yourself with a Gunson Carb Balancer and Colour Tune and have a go yourself. It's not too difficult and very rewarding. Have a look on eBay as the two are often sold as a kit for not too much money. Cheers, Steve Quote Link to post Share on other sites
Peter Cobbold Posted May 23, 2015 Report Share Posted May 23, 2015 It you can't find a good garage then perhaps arm yourself with a Gunson Carb Balancer and Colour Tune and have a go yourself. It's not too difficult and very rewarding. Have a look on eBay as the two are often sold as a kit for not too much money. Cheers, Steve Steve, That will work if the carbs have the correct spring and needle for the engine. The colortune allows the jet to be adjusted at tickover - about 2horsepower . Mixture prepartion at higher loads will then be correct only if the carb is to spec. A more flexible way is to fit a wideband air fuel ratio ( AFR) sensor in the exhaust so the mixture can be checked while driving at a range of loads. Peter Quote Link to post Share on other sites
graeme Posted May 23, 2015 Report Share Posted May 23, 2015 A more flexible way is to fit a wideband air fuel ratio ( AFR) sensor in the exhaust so the mixture can be checked while driving at a range of loads. Hi Peter, I am considering fitting an AFR sensor, is there a preferred position in the exhaust system? Cheers Graeme Quote Link to post Share on other sites
RogerH Posted May 23, 2015 Report Share Posted May 23, 2015 Hi Graeme, if I had one of those hi-tech AFR thingies the correct position would be the glove box Roger Quote Link to post Share on other sites
Peter Cobbold Posted May 23, 2015 Report Share Posted May 23, 2015 Hi Graeme, There are two requirements. The exhaust temp should not exceed 750C. And the engine should never be run until the electrical heater has brought the sensor up to operating temperature. So it needs to be switched on ca 20 seconds before engine start. Mine is going at the end of the downpipes just before the first joint, alongside the starter, using the longer boss to keep the snout out of the direct exhaust stream. It will be in use all the time. But for temporaory measurements the tailpipe site would be suitable as long as the exhaust pipe joins are gas tight. Much more info here: http://wbo2.com/lsu/position.htm Bosch make the sensor, other companies use them in their kit eg AEM, Innovate etc. Peter Quote Link to post Share on other sites
Ernest Posted May 23, 2015 Author Report Share Posted May 23, 2015 Hi all Thanks very much for these suggestions.....I very much appreciate the range of thoughtful and informed advice. I don't really want to take the car back to the co. I bought it from mainly because this would involve a 300 mile round trip and I am not all that confident that they will resolve the problem - given that they set the new carbs. up initially. It looks like I need to check technical points raised by Peter and Roger. Then, if all OK, either purchase the tuning bits as Steve and Peter suggest, or seek a reliable garage such as Trevor notes (really good to meet you too last Weds Trevor) - I am tempted to have a go at the tuning myself (as this would have a longer-term value) then, if I make a hash of it I can then use a recommended garage as a back-stop. Thank again all Best Wishes Ernest Quote Link to post Share on other sites
Peter Cobbold Posted May 23, 2015 Report Share Posted May 23, 2015 Ernest, Have a go - excellent ! All you need now is the specification of the needle and the spring for TR4. Then you could simply fit new items. This is a good starter article: http://sucarb.co.uk/technical-su-carburetters Peter Quote Link to post Share on other sites
Kiwifrog Posted May 23, 2015 Report Share Posted May 23, 2015 If the carbs can be correctly set at fast idle but do not give correct performence under load I would suspect you have the wrong needles for your application. The carbs should have a tag somewhere indicating what they are set up for. Once you have this reference you can then start looking at solutions. HS6's were used for lots of cars, I have a pair of NOS ones from a morris marina GT which I use on my 3a with a TR4 spec engine after sorting out the right needles and making up some linkages. Most needles have their specification number on the needles themselves (in very small writing) Alan Quote Link to post Share on other sites
McMuttley Posted May 23, 2015 Report Share Posted May 23, 2015 Ernest, if you want to know what knackered SU's sound like, just listen to me driving around the Borough ! A friend at Brands Hatch gave me the name of a SU Specialist in east surrey, I will dig it out tomorrow. I cannot recomend anyone local! Where in Bromley ? Quote Link to post Share on other sites
trevor Posted May 24, 2015 Report Share Posted May 24, 2015 Forgot to say the reason I mentioned Sanspeed is because they have a rolling road , and it's used by a Classic Rally prep chap in Blaclpalfrey Motor club .. Quote Link to post Share on other sites
Ernest Posted May 24, 2015 Author Report Share Posted May 24, 2015 Hi Thanks Trevor for clarification and Alan for useful info. re. carbs. Hi McMuttley - I live I Hayes and as yet I haven't heard you TR passing!! Thanks again all for contributions. Ernest Quote Link to post Share on other sites
lynchpin Posted May 24, 2015 Report Share Posted May 24, 2015 Hi You could look up Burlen Services and give them a call they specialize in fuel systems and are very knowledgeable on SU Carbs, they should be able to advise you of the correct needles and springs your car should have and how to check this.. Cheers Phil.. Quote Link to post Share on other sites
Ernest Posted May 24, 2015 Author Report Share Posted May 24, 2015 Thanks Phil I can see that from their web-site that they would be able to supply standard parts for the carbs. So, if I do need to change the needles back to standard, I can use them Thank again Ernest Quote Link to post Share on other sites
doretti Posted May 25, 2015 Report Share Posted May 25, 2015 Hi, Can anyone suggest a reliable garage in the Bala, North Wales area with experience of tuning twin SU carbs? Ken Quote Link to post Share on other sites
Peter Cobbold Posted May 25, 2015 Report Share Posted May 25, 2015 (edited) Hi Ken, Ask for Andrew Ellis who works at Automark, Rhuthun: http://www.automark.info/Contact.html He lives and breathes classics, does all that garage's classics work. Peter ( in Derwen ) Edited May 25, 2015 by Peter Cobbold Quote Link to post Share on other sites
doretti Posted May 25, 2015 Report Share Posted May 25, 2015 Peter, Thanks for your recommendation. Ken Quote Link to post Share on other sites
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