Replace HD6 with HS8 Dilemma

Hello. I am tinkering with a '53 XK120 SE OTS. I was ‘encouraged’ to fit 2" HS8’s and I am disappointed with the low down torque (ie off the line power) they have delivered. They are quite a bit better higher up the rev range but I really wanted to improve the off the line power.

It is a 3.4 with an SE head (not C type), both inlet ports reamed to 2". The engine was rebuilt 1000 miles ago. I have trumpets with foam covers. The needles are standard XJ6 BAW. Powerspark ignition.

Is there any way I can dig myself out of this hole. ? Maybe retard the ignition a tad ? Different needles ?

Any wisdoms gratefully received.


First isolate it to being mixture and tune it richer, trial run, if it is worse go leaner.
Then either try other needles or measure and file them to suit, I guess.
You know the website?

Actually this is useless, a standard 3.4 with standard head will not gain from going to HS8 carbs.
The only gain you get is higher fuel consumption.


Hi there:

This is quite true: the breathing ability of the inlet/head is the limit, not the carbs in this case.



Yes… go back to the original carbs: they are MORE than adequate for that car.