B18B P1800 SU Carb Needles
 

Hi All,
I have been reading lots of the threads with enjoyment, and would like to introduce myself, I have a P1800 and I have been slowly getting it mechanically ready for the last 2 years, I have rebuilt almost every mechanical item and I'm ready to the HS6 Carbs.
I have rebuilt the B18B emgine with a "C" Cam, and oversise 0.040" pistons, the rest is standard with the standard single downpipe exhaust.
I assume my engine would be a type 2 or 3 but i'm not sure the difference,
The Question is what carb needle should I be considering, should I be going for the ZH or KD.
Any assistance greatly appreciated.
Steve...

Steve;

Welcome to this forum!

Congrats on you acquisition of a P1800...you don't mention the level of experience or past contact with SU carbs, so I suggest with a low risk "familiarization", and see where it goes from there...see: https://www.sw-em.com/SU%20Carb%20Service.htm

Why do you ask about the Metering Needles...I expect you got some appropriate ones to start with but KD, KN, ZH are all standard for the Volvo configurations.

Cheers from Connecticut!

Hi Connecticut,

Thanks for the Welcome!!,
I also have an MGB which I rebuilt the carbs on, but I didn't change the configuration of the engine at all, so I retained the same carb Specs, I did the rebuild myself, I am an aircraft Mechanic so I have access to good tooling.
I have always also tuned the carbs myself,

I have rebuilt the p1800 engine but the specs are different from original, eg the cam has gone from "B" to "C" and the pistons 0.040" oversize,

I have rebuilt the carbs with the original TZ needles installed
the engine runs well but to get them tuned, the jets are wound down quite a bit, at least 2 extra full turns from before

I was thinking that the original needles are too lean for the new config I am using, but I don't really know which new needles to try.

I havent as yet road tested the car, maybe I should wait and see what it drives like first?

Steve..

Personally think if you've done some small engine mods then best way is to use a O2 wideband sensor and gauge to get the correct fuel mixture, takes the guess work out. I would start with the standard needle for the engine and ensure fuel ratio is set correctly at idle as per Volvos instructions. You can then plot the needles here for comparison to help chose: http://www.mintylamb.co.uk/suneedle/

For SUs I would shoot for the following air fuel ratios, they will vary a bit with the SUs when looking at the gauge:
Idle - 13.2:1
Cruise 14 to 15:1
WOT 12.5:1

Thanks Burdekin,

I like the Needle comparison page, it looks like the needles for the type 2 and 3 engine are richer at medium to high revs,

I will look for an O2 meter/sensor, it's a very good ides as it will also help me out with other cars, I will then proceed from there.

Thanks,
Steve

I just have the Innovate O2 wideband, works a treat and not expensive. It is temporarily fitted and powered through the cigarette lighter. Another handy tool I have is this multimeter that can read rpm. https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1

When setting mixture keep on winding down the jets until they don't increase rpm anymore, then wind back up one flat. Easy with the multimeter. That should set your fuel mixture about 13.2:1 and is how Volvo recommends it's set.