BigT_DK wrote:My spitmkIII (standard worn oil pissing engine, but with K&Ns and extractor manifold) runs on AAQ needles... Thanks, it appears from all online reading, AAQ seems to be the needle I should get michael_charlton wrote:http://www.mintylamb.co.uk/suneedle/ Have a play around Thank you, I have found that site and the other link where it lets you enter values for a given needle sector, then bring up all matching needle. But my problem is that I don’t know how to put that cart in to real life as I have had no experience in swapping needles. 4058 wrote:When you say dyno tune, do you mean a guy with a diagnostic computer, or a rolling road? It was a roller dyno. I agree, no tuning is real tuning unless it is road tuned or dyno tuned. He also had Bosch ETT connected. Maybe it is the good mechanic part that is missing here. I may have to take it somewhere else to get a second opinion. 2674 wrote: I spent ages trying to track it down in the end it was poor float chamber needles that would let the float chamber over fill at idle then empty out at higher revs, they looked perfect when inspected but obviously weren't. These carbs were rebuilt beginning of the year, they ran somewhat okay. Used to miss on high rpm, eg. above 3.5k or so. But that something worth checking again. 2674 wrote: As you have an electronic fuel pump you could also have an over pressure problem, if the pump is too strong for the float valve you will get the same problem the float chamber will over fill at idle. I think the correct pressure for SU systems is about 3 PSI (I am sure someone will correct me if I am wrong). This very well can be the issue here. I have found that pump runs between 3-4 psi. yes, you are correct, pressure for my car, I believe is 2.5 to 3psi. 2674 wrote: I am guessing you have checked this as well but if your carbs were recently rebuilt it would also be worth checking the needles a re centred correctly. Thanks, I have done that. I have also done usual troubleshooting on manual, like timing and valve clearance etc. Since posting here, I have found that BO needles are infact correct needles for Mk 3 1300. Float chamber tags have AUD257 - can someone with a MK 3 Spitfire confirm that for me? Many thanks in advance to all of you.