B18 needles for a D grind cam

[Juular]

The engine in my car is a B18B with twin SU carbs and high compression head. While rebuilding (more accurately, refreshing) it I noticed that it had a D grind cam installed which I simply reused.

Since balancing, tuning and timing, the engine pulls exceptionally well through the low - mid range. However I've noticed that if I try to rev out the engine, say past 4500-5000rpm, it starts pinking.

In normal driving it does not pink at all and the dizzy seems to be functioning perfectly, advancing up to around 30 degrees at 3000rpm.

Mix seems good for normal driving and plugs look a nice sandy colour.

I have no idea what needles are currently in the carbs but am I right in thinking that the needles should have been changed to match the cam? I suspect it may be too lean at higher rpm.

What needles should I be using for this setup?

[northNH]

Plenty of SU needle info out there, as detailed as you want to go.
There are hundreds of size/taper choices.

Start here with just the tiny segment that were used in B18/20s SUs:

http://www.networksvolvoniacs.org/im...edle_Types.pdf

KD,KF, DX the richest overall, but differ subtly…

[Juular]

Nice. Thanks.

Are there identifying marks on the needles so I can work out what I already have?

Forgive me I'm more used to EFI and CIS.

[gjr0]

There are letters stamped on the top portion of the needle. Sometimes they are very faint.

[Rustinmotion]

If you remove the needle you have to re centre the needle to the jet when re assembling it’s not hard but don’t assume it’s just to swap needles and go

[Salop Farmer]

I have same B18B with D cam 10:1 CR and KD needles in carbs. This was Rally car set up of late 60’s. My experience so far is good although as I am running rebuilt engine in I have not ventured above 3500 rpm. Tick over 900 - 1000rpm and always on the rich side!

[Ron Kwas]

J;

A good light on the subject will help to ID Metering Needle punched markings. Example:

Source: http://www.sw-em.com/SU%20Carb%20Service.htm

If throttle response (which can be adjusted slightly with Mixture Adjustment Nut) is good, and sparkplug inspection also, the KD MN is probably fine with your D Cam...optimum would of course be an exhaust test with wideband O2 sensor and on a Dyne...

Cheers

[Derek UK]

The problem with checking the needles is that they are usually very difficult to remove without bending them. They are usually stuck so get some solvent into the fixing screw hole and maybe drop the piston in very hot water. Even a few minutes in the oven. Think about what you are doing and be careful