SU's on V8 110 Running Lean?

[japspeed]

I am battling to get the SU's to run properly on my 89 V8 110. Symptom: Runs fine when cold, when warm starts jerking, feels like fuel starvation. When I tap off, she runs properly. Foot down, jerks again. Started after a long 8 hour run flat out (my normal driving style).

I have done the following:

- Replaced all seals on carbs, including both sides of throttle butterfly shaft;

- Replaced fuel pump;

- New fuel filter;

- Blocked off PCV pipes on carbs & routed crankcase breathers into catch can - made a huge improvement;

- Turned idle mixture screws 3,5 turns rich after ensuring that main jet is level with bridge;

- Balanced carb airflow equally;

- Made sure fuel pickups in float chambers are facing inwards;

- Checked float levels;

- Cleaned out carbs thorughly;

- Checked height of needles - collars level with body of piston.

All of the above have improved matters greatly, but still jerking. It feels as if it leans out when warm - what about the bi-metal thingys that hold the jet in place?

Cheers,

Japspeed.

[101sean]

What about the fuel pick up, does it have a clogged or collapsed sock on the end (common 101 problem)

Other thought, is your coil breaking down when hot?

[Quagmire]

Have you checked the dashpots? Could they be sticking? Jerking on application of throttle is definitely a symptom of lean condition as far as i know. If the pistons are sticking too far down you'd get rich, but too far open and you'd get the opposite.

I had similiar at first when setting up my LPG vapouriser. My idle bypass was too far closed, the result was that you had a kind of "digital" throttle effect. You had to push the throttle quite far before it did anything, and no matter how gentle you were it still gave the on or off feeling. Terrible in slow traffic, not good for the transmission either!

[japspeed]

What about the fuel pick up, does it have a clogged or collapsed sock on the end (common 101 problem)

Other thought, is your coil breaking down when hot?

Good point on the coil, hadn't thought of that. Does the coil get progressively worse, or just pack up completely?

[japspeed]

Have you checked the dashpots? Could they be sticking? Jerking on application of throttle is definitely a symptom of lean condition as far as i know. If the pistons are sticking too far down you'd get rich, but too far open and you'd get the opposite.

I had similiar at first when setting up my LPG vapouriser. My idle bypass was too far closed, the result was that you had a kind of "digital" throttle effect. You had to push the throttle quite far before it did anything, and no matter how gentle you were it still gave the on or off feeling. Terrible in slow traffic, not good for the transmission either!

Thanks Quagmire - is there a way to check if carb piston/s are getting stuck up , or going up too far when hot causing it to lean out?