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I have a 1070 engine with a big valve (37/31) head, 296 cam and twin HS 4s.

Anyone here with a recommendation of needles, where I can start ?

You've asked a question that is absolutely impossible to answer with any degree of accuracy. That's because there are just soooooooo many variables.

Your best bet is to hope that what you have said rings a few bells with them and they'll come up with what works in their car with a similar set-up. When it's running, take it to a rolling road tuner with a vast selection of needles and he'll set it accurately.

That's my answer to the impossible question.

I know that it is not easy.

But I want a point to start.

almondgreen wrote: ↑Wed Aug 30, 2023 7:46 am I have a 1070 engine with a big valve (37/31) head, 296 cam and twin HS 4s.

Anyone here with a recommendation of needles, where I can start ?

Hi, if you can stay put until later today, I will check my records. I may have some starting point for you.

Besides, if you don't have access to a rolling road setup facility it is adviceable to fit a thread for a wideband Lambda sensor to your exhaust manifold and plug it to an AFR data logger like Zeitronix https://www.zeitronix.com/Products/Zt-3/Zt-3.shtml
But you probably know that anyway

I would start with E3 and blue springs and go from there

I have a 1293 A series, big valve 940 cyl head APT 285 cam twin HIF 38s large center pipe LCB. On paper 11.3 t0 1 C/R. Running on my test stand with O2 gauge hooked up fully rich adjustment it begins to lean out with RPM. I'm running floating needles AAA currently but will give AAB which are richer a try once back in car with O2 gauge hooked up. Steve (CTR)

Just consulted my WinSU app and with a roughly similar setup it recommends AAN needles.

whistler wrote: ↑Wed Aug 30, 2023 3:04 pm Just consulted my WinSU app and with a roughly similar setup it recommends AAN needles.

I like WinSU for comparing needle profiles but unfortunately Ive found its needle suggestions for particular engine specs to be well off the mark.

If you want a fixed needle then CP4 and MME were suggested by special tuning on H4 carbs. They’d get you a decent place to start from

I agree with imack, WinSU great for comparisons, but not even close for recommendations.

Only a hint:
when I used Twin HS4 on my 998cc racer I utilised AAA needles with blue springs. I tested this setup with colortune and in general the plugs had the right colours too. I later went to 45DCOE with the Maniflow steel inlet but, of course had to modify the body to fit the setup.

Good to see colortune mentioned R-tec. I am a great believer in it too, especially for initial start-up revs.

The trouble is that the average Joe would need a whole lot of various needles...... plus a true in-depth understanding of the mechanics of the carbs, the physics of burn rates.

Only just seen this. Use a pair of MME's, they "may" need richening up a bit ove the last 1/3rd, but they will certainly get you within striking distance. I haev built many engines of that spec, so I ain't guessing.