Which Needles Tripple SU

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344739lv
Posts: 52
Joined: Thu May 01, 2008 11:30 pm

Which Needles Tripple SU

Postby 344739lv » Sun Jun 02, 2019 9:22 am

Can anyone help?

I am running a freshly rebuilt series 2 DHC - rebuilt engine and carbs etc etc.
The car has open trumpets as the air box has been removed.
It runs perfectly at low speeds but is too lean on acceleration and at speed.
I am running UM needles and was thinking these are part of the problem. My thoughts are moving to UE or UB (UO probably too rich) - but wondered if anyone had a view.

Also running a 123 distributor- compression and valve timing as well as ignition timing all perfect.

General running also perfect.

Any help appreciated.

Tim

MikeNewton
Posts: 1
Joined: Fri Aug 19, 2016 12:14 am

Re: Which Needles Tripple SU

Postby MikeNewton » Tue Jun 18, 2019 12:05 am

Tim,

I can’t really help with the needles but am interested in the 123 ignition set up.

Is the distributor blue tooth, and if so, what advance curves did you set?

Mike

PPV
Posts: 519
Joined: Sat Jun 14, 2008 4:48 pm
Location: Nantwich

Re: Which Needles Tripple SU

Postby PPV » Tue Jun 18, 2019 12:26 pm

How do you know it is running too lean at speed?
Regards,
Paul V
Mk2 3.8
Mercedes A45 AMG
Mercedes AMG GLC43

344739lv
Posts: 52
Joined: Thu May 01, 2008 11:30 pm

Re: Which Needles Tripple SU

Postby 344739lv » Fri Jun 21, 2019 10:12 pm

Mike, it’s not a Bluetooth set up - i’ll Check what advance curve and revert (the 123 was installed by a pal) - it is going well but I don’t know if I notice a real difference from a standard distributor to be honest.

Paul - re the lean running at speed - gentle acceleration was causing a hesitant “flutter” and the car felt very underpowered. Hard acceleration resulted in backfire through the carbs. I have kept the UM needle set up but richened the mixture - now reading 13 in CO2 previously 6. I also had cooler plugs (NGK 6ES) which I have changed to standard 5ES hotter plugs to avoid fouling with the richer mixture. The result seems very positive. Good running - good acceleration now - although conscious that it is not very rich co oared to before.

Tim

344739lv
Posts: 52
Joined: Thu May 01, 2008 11:30 pm

Re: Which Needles Tripple SU

Postby 344739lv » Fri Jun 21, 2019 10:14 pm

Last post should end “now very rich compared to before”

344739lv
Posts: 52
Joined: Thu May 01, 2008 11:30 pm

Re: Which Needles Tripple SU

Postby 344739lv » Fri Jun 28, 2019 7:30 pm

Mike,

I promised to revert with the ignition curve setting in my 123.

It was set up on curve 2.

However only a couple of weeks in and the 123 seems to be failing! Misfires under load despite the set up being as per set up instructions.

Swapped it back for a standard dizzi and all is well! Will check again thoroughly when I have more time - and check the coil (although I have a new one) but at the moment the car runs fine on a standard Powerspark £70 dizzi and performs poorly with a 123.

Tim

344739lv
Posts: 52
Joined: Thu May 01, 2008 11:30 pm

Re: Which Needles Tripple SU

Postby 344739lv » Sat Jul 06, 2019 5:16 pm

Mike,

The new 123 dizzi WAS at fault, in fact when examined by engineer we noticed various burn and arc marks on the inside of the 123 dizzi cap.

Car now running like a dream on a new Powerspark dizzi, Coil and leads - OE needles and NGK 5ES plugs. These have been in for around 300 miles now - lovely colour no fouling - completely opposite to the situation under the 123 Dizzi.

May be that I was unlucky but I certainly won’t be using 123 dizzi again. Very expensive - failed within a couple of weeks and when it WAS working it didn’t change anything over my standard dizzi - certainly no better.

Tim


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