Guest Karlbristol Posted May 26, 2004 Report Share Posted May 26, 2004 Hi everyone, I've not had the car that long (1979 2lt) and although it's running a lot better than it did when I got it, it's still not doing what it should. All I've basically done is (as some of you know) replaced the electronic ignition and put new plugs in. This has made the car a lot easier to start and it doesn't cut out at lights etc. when I apply a little choke. The carburettor needles were rich BAP ones (please see my site for the SU carb needle chart) but I recently got the standard BDM ones. I fitted K&N filters to it the other day and put in the BDM needles and it was actually running worse so I put the BAP's back in last night and there is a definate improvement. Since I've had the car I haven't speeded in it at all and I think the fastest we've gone was a brief 80 on the motorway. We didn't keep it at 80 for too long as it was screaming a bit. I've taken the car out today and although ticking over reasonably well, as soon as I open her up a bit, as soon as I get to around the 3,500 - 4,000 rev it's pinking like hell (if pinking is the word I'm looking for here) which basically means, the engine is kinda red-lining at about 4,500 and at that point there is no more power. There haven't been any major mods done to the engine 'yet' as I plainly can't afford them or a new - uprated - engine but it does have a fast road camshaft. Can anyone point me in the general direction of what might be wrong ? I'm suspecting that the leads might need changing and maybe the vacumm hoses could do with replacing and the rubber mounts on the carbs have probably seen better days and they, too, could be replaced. Is it something else, timing, etc. ? or should I get someone to have an expensive look at it ? Thanks for your help. Karl Quote Link to post Share on other sites
malcolm Posted May 26, 2004 Report Share Posted May 26, 2004 Karl. Did you get the carbs set-up properly? This is most likely the problem. Even if they are a little worn it will make the world of difference. When I first ran my 7 after changing the engine (& inlet manifold) it did just what your's is doing. A couple of hours getting it into a passable state of tune and it drives OK. Now I just have to replace the water pump..... SU tune-up document Malcolm. Quote Link to post Share on other sites
andrewt Posted May 26, 2004 Report Share Posted May 26, 2004 Hi Karl I have forgotten most of the details on specific needles, but if you have K&N filters fitted and a fast road cam, then the engine is going to have significantly changed in its fuel demands, more so as the revs rise & the cam starts to be noticeable. As such the standard neddles will definitely be too lean. However that is not to say the other ones you have are right either. I would suggest calling some of the companies who are regularly tuning & supplying needles to see which ones they suggest. You may even find someone who will let you try a few different ones before committing to one pair. Be careful because if you run with too lean a needle for any time at all at high engine speeds you could do serious damage to your engine! S&S preparations may be a good place to start as i always find them to be very helpful. Cheers Andy Quote Link to post Share on other sites
Guest Karlbristol Posted May 26, 2004 Report Share Posted May 26, 2004 Thanks Malcolm and Andy. I'm going to use your document, hopefully tomorrow Malcolm Andy, I'll get in touch with S&S and see what they can do. I know there's loads more in the engine and think that malcolm has a point, but as to which needle... the chart I found is of no help to me whatsoever even with my engineering background. Karl Quote Link to post Share on other sites
marvmul Posted May 26, 2004 Report Share Posted May 26, 2004 Karl, you're mentioning the rubber mounts : this could well be the problem. You're car seems to run much too lean with the standard BDM needle's. The BAP needles are much richer. Perhaps there is an air leak (on the rubber mounts) and this weakens the air/fuel mixture a lot. So I would replace these mountings, you can also remove the vacuum pipes and close the pipe connections on the carbs. As a start, bring the jets flush with the carb bridges and then turn them down about nine flats. With BDM needles, the car should run fine if everything else is ok even with K&N air filters. The pistons should fall freely after lifting them by hand. Look at the pistons when blipping the engine : they should rise equally. An oir leak can be located with special spray, but also spraying WD40 in the direction of the supposed air leak will change the rpm of the running engine if there is indeed a leak. Quote Link to post Share on other sites
robgeev Posted May 26, 2004 Report Share Posted May 26, 2004 Look at the pistons when blipping the engine : they should rise equally. An oir leak can be located with special spray, but also spraying WD40 in the direction of the supposed air leak will change the rpm of the running engine if there is indeed a leak. Lighter fuel (butane-not Zippo) is very good for finding air leaks, without the mess and secondary incendiary issues, we use it to find problems on LPG conversions all the time. I would agree with the lean mix/ strangled fuel supply ideas though. Rob. Ps.How do you like the carrot? Quote Link to post Share on other sites
Guest Karlbristol Posted May 27, 2004 Report Share Posted May 27, 2004 Thanks for all this.. I put together a bit of a spreadsheet to see the differences in some of the 300 needles.. You'll be able to see it here. http://www.thamesmarketing.com/tr7/articles.htm and there is a much lengthier post here: http://www.forum.triumphtr7.com/ Karl Quote Link to post Share on other sites
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