Which needles........
Posted: Sat Mar 05, 2011 8:36 pm
........not to be confused with a similar thread a few months or so back!
Some of you may recall my threads about a year or two back as well as an item in the DM about my Sprint pinking heavily while storming up Haldon Hill near Exeter on the A38 in which I described as more of a spitting sound (like if you were to spit onto a hot plate of an iron to test how hot it is and the spit is bounced off the hot plate with a sharp hiss/spit sound).
Well, as this is still happening and, following a rebuild at the time requiring four new pistons as two of the piston lands and rings had virtually disintegrated (!!) which I am keen not to repeat, I decided to contact a guy in Plymouth who has been in the tuning business for over 30 years and who has a dynomometer. The results were in the main quite encouraging as the car seems to be set up pretty well but, the downside was that I may need some new needles. The pinking was, in the tuning guys opinion, not just pinking but detonation which, if the engine was to be driven under these conditions for a lengthy, continuous period, would result in total piston failure. The carbs (standard 1.5" SU) currently have the factory recommended BCM needles but the dyno print out suggests that the engine is running weak at the higher rev range (3 - 5k revs at about 50 - 70mph).
Is there anybody out there running a similar set up with different needles ie thinner at the pointier end and if so, what needles are you using?
Cheers
Some of you may recall my threads about a year or two back as well as an item in the DM about my Sprint pinking heavily while storming up Haldon Hill near Exeter on the A38 in which I described as more of a spitting sound (like if you were to spit onto a hot plate of an iron to test how hot it is and the spit is bounced off the hot plate with a sharp hiss/spit sound).
Well, as this is still happening and, following a rebuild at the time requiring four new pistons as two of the piston lands and rings had virtually disintegrated (!!) which I am keen not to repeat, I decided to contact a guy in Plymouth who has been in the tuning business for over 30 years and who has a dynomometer. The results were in the main quite encouraging as the car seems to be set up pretty well but, the downside was that I may need some new needles. The pinking was, in the tuning guys opinion, not just pinking but detonation which, if the engine was to be driven under these conditions for a lengthy, continuous period, would result in total piston failure. The carbs (standard 1.5" SU) currently have the factory recommended BCM needles but the dyno print out suggests that the engine is running weak at the higher rev range (3 - 5k revs at about 50 - 70mph).
Is there anybody out there running a similar set up with different needles ie thinner at the pointier end and if so, what needles are you using?
Cheers