Relative jet heights on full choke

[ALAN COCHRANE]

Hi Everyone

I've just finished rebuilding the twin HS6 carbs on the Triumph and set up the initial jet heights:-
On the first carb that means two full turns down on the adjusting nut, measure the depth with a micrometer (48 thou in this case) and then set up the second jet accordingly.
All good so far. Out of interest I decided to check the jet depths with the linkage fully engaged, ie when the choke is fully on. Carb one was 235 thou and carb two was 285 thou. This was the closest I could get them even after some judicious bending of the connecting rods to the jets.
I realise that this will only have an effect when the choke is used but is this difference normal?

Cheers

[mgcjag]

Hi Alan....wrong forum or did you mean to ask here. ....Steve

[ALAN COCHRANE]

Hi Steve

I did mean to post here. Although it's about the GT6 carbs, the common link is that they are SUs. In any case GT6s left the factory armed with a 2l engine and Stromberg CD150s. My car now sports a 2.5l engine and HS6 SUs.
The level of expertise and depth of knowledge here is unparalleled so I thought I was much more likely to get a definitive answer.

[mgcjag]

HS6 are quite different ftom HD8......you said it isnt causeing a problem as its only when on choke....but yes they should be the same in an ideal world...but thats not always possible with linkages .....Steve

[cactusman]

My MGB has HS4 carbs.....slightly smaller but same principle....On choke both jets move down by roughly the same amount but I've never checked to see if they are identical. In my opinion a small difference won't make much difference to the operation of the choke...they move a long way down to ensure a flood of fuel . Probably more important to make sure that once you let the choke off back to the fast idle position when the jets are now back up but the butterflies held slightly open that they are both held open to the same degree....just my hunch....my MGB almost never fails to start first time...

[PeterCrespin]

The level .... and depth ... here is unparalleled....

So are your jets. These’ll fix it:

[ALAN COCHRANE]

Julian

They were my thoughts as well. I never checked the carbs before I rebuilt them so don't know if the difference was always present. I didn't bother to check the E-Type's carbs after their rebuild either. They may well have the same discrepancies.
The Triumph had "Frankenstein" carbs before the rebuild. Consisting of cut down bells from a Rover SDI which worked well but they're now sporting pukka Dolomite Sprint carbs.
The reason being that the bonnet clearance on the forward bell is extremely marginal-only 2 to 3mm at best. In fact if you press the bonnet down with your hand you can feel the top of the carb.
Anyway I think I'll leave well alone and if the choke works then I'm happy. I need to stop over analysing things.

[malcolm]

Julian

I need to stop over analysing things.

Youre like me Alan! I overanalyse everything. Nearly had my engine taken apart at great cost because of needless concerns. Fortunately saw the light of day, a few checks, and found everything was fine.