4 replies to this topic

[Danyul1275]

Hey guys, I have a 1275 engine running twin HS4s and I'm having a few problems tuning my carbs and i just wanted to check the ignition system before i make a mess of everything, just wanted to know what the gap settings should be on my spark plugs and what the point settings should be on my distributor?
Also any tips on tuning them to there full potential whould be great

cheers
Dan

[finch661]

would of thought that twin hs4s on a 1275 is a bit over kill?

[Danyul1275]

would of thought that twin hs4s on a 1275 is a bit over kill?

Nah they've been fine up untill 2 weeks ago when I managed to crack one of the float chambers, so i put a new chamber on put a service kit on them and now I'm just having trouble tuning them.

[finch661]

best thing to do is to start from scratch

first of all, did you remove the cars/manifold to fix the float chamber? recheck that there are no airleaks (i spent ages trying to tune my hs2's until i found a gap between the manifold and head)

i would screw the mix nuts up, untill the jet is level with the bridge, then turn the nut 2 full turns (12 flats) (remove the dashpot and piston to see this), refit the piston etc, screw the throttle screw all the way out, then in two turns. this should be enough to get the car running.

then use a carb balancer and colortune to check everything

[dklawson]

In answer to the ignition questions, I believe the points gap is 0.015" for any Lucas dizzy. The spark plug gap can be opened or closed a bit depending on what you are trying to achieve but nominally 0.025" would be OK. The ignition timing really depends on your engine, its state of build, and the fuel you use. There will be "text book" numbers to start from, but I tune for a maximum advance around 32 BTDC at 4k RPM. As a basic starting point you could set the static timing around 8 BTDC. That should at least get the engine going so you can work on the mixture.