SU Carbs

[beandip]

Pulled rear SU down today and found that needle was slightly off centre when rolled along bench. This is probably part of my problem, Can someone tell me where I can get a set of N-27 needles in Australia. Called SU Midel but they only do English SU's.

Glen.

Has any one asked if these are 4 screws or 3 ? The needles are easy to straighten by the way. Why I asked about which SUs you have is the 4 screw have a adjustable nozzle holder, the 3 screw have alignment plastic pins on the top of the carb base to align the dome and all that it holds. If the needle shows wear at all, look VARY closely at the nozzle because it could likely be worn also. Nissan may still have 27s I bought a set recently here in the US . They were available for the '70 240 Z . Nozzles on the other hand are no longer available as far as I know , at least in the U.S. If you need a nozzle contact me by PM . This might be part of your problem , however I think much of the flat running at low Rs is due to a radical cam and low engine vacuum at the low end . This is why , I think , she comes alive in the upper end . this was a concern of mine because of my cam. This is why I mentioned what I have in my car and how it runs with SUs . SUs will supply 280s to 6K or so , if that is what you are looking for . Up in that range you might be better suited with triples. Gary

[Zedrally]

post #5.

Still none the wiser as we haven't been advised.

[Glen]

SU's have 4 allen screws holding down the domed outer sleeve. I believe they are Hitachi. Please explain the nozzle, is this the sleeve that the needle slides through? How can I check my vacuum is correct at low rpm? Can I straighten the needle with gentle heat and rolling it between two pieces of flat bar?

[Zedrally]

SU's have 4 allen screws.

oops, both my 240 & 260 I have have phillips head type screws.

Maybe yours have been swapped out by a PO or mine may have been swapped or....you may not have hitachi SU's.

Time for more input by others.

[Glen]

Sure that the allen screws have been a later addition as they are very new looking, stainless steel items. I assume the older screws were just worn or had been deformed.

[=Enigma=]

You can straighten the needle by spinning it in a hand drill chuck at high RPM while pushing it against a rag held in your hand or on a bench. You will see the wobble while it's rotating. Use gentle steady pressure to straighten it out. I recommend a little oil to reduce the friction and minimize the possibility of wear on the needle. Use a clean rag.

[Glen]

Thankyou all who gave advise. Have straightened the needle and replaced oil in SU's with 3 in 1 sewing machine oil, a few tweeks with the mixture and idle and away we go, car is running a treat.

Thanks again guys.

Glen