The Triumph Dolomite Club - Discussion Forum

........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

Just an update on my earlier thread.

Firstly, I mentioned I had 1.5 in SU carbs but should have said 1.75s as the Sprint has HS6 which is 1.75. Also, interestingly, I said that the carb needles currently fitted are BCMs, which is what the official Leyland Workshop Manual lists (these are the brown plastic covered type which allows the pages to be removed/replaced).
I have two of these - issue one just shows just the carb type and venturi size but issue two shows an amendment indicating the needle is BCM. However, the Haynes manual, my original Sprint Owners Handbook (given to me when I first bought the car), and various Rimmers sales stuff show the needles as BBT. Not sure why two official Leyland publications would have two different specs.

Anyway, a search through my box of bits found two good nic BBT needles which I shall fit and give the Sprint a burst up some suitably steep hills and see what the difference is. As the dyno print out yesterday showed that the engine wasn't reaching full power at the higher rev end I hope that the BBT needles will help.

Yellow Banana wrote:Not sure why two official Leyland publications would have two different specs.

That'll be because BL, bless 'em, didn't know whether they wanted a sh*te or a haircut. I've two copies of a 1973 parts book and those differ in quite a few of the part numbers listed, so small wonder that the same level of care went into the brown book.

ive recently changed from bbt's to bdq's as i found the bbt's a little to rich,i am running k+n's so not sure if that makes a difference,obviously not all engines run the same, check out this link to compare different needles ,the bbt's where fitted to early sprints and bcms and bdq's on later versions ( i think bdq's where on the last sprints ) i think the change of needles was down to the later cars running the awful ( well in my experience ) waxstat jets and to keep emissions down
http://www.mintylamb.co.uk/suneedle/

BDQ