Twin SU’s full throttle

[packers1712]

Good morning all,

I've finally managed to attach some photos of the butterfly positions when operated from the pedal compared to directly at the carburettors, photo 1 is pedal and photo 2 is direct.

Doug.

[Burdekin]

Originally Posted by packers1712

Good morning all,

I've finally managed to attach some photos of the butterfly positions when operated from the pedal compared to directly at the carburettors, photo 1 is pedal and photo 2 is direct.

Doug.

Have you got some photos of the linkage? Have you set it up so at idle it's sitting just proud of the stop on the manifold?

[packers1712]

Originally Posted by Burdekin

Have you got some photos of the linkage? Have you set it up so at idle it's sitting just proud of the stop on the manifold?

Hi Mitch,

No photos of the linkage sorry I'll get some tonight and I'm not sure on the set-up with reference to the stop, I will also check that!

Doug.

[Wagon Sailor]

Originally Posted by packers1712

Good morning all,

I've finally managed to attach some photos of the butterfly positions when operated from the pedal compared to directly at the carburettors, photo 1 is pedal and photo 2 is direct.

Doug.

They look OK to me.

[packers1712]

Originally Posted by Wagon Sailor

They look OK to me.

Do you reckon they are open far enough, it just seems odd that the linkage can't open them fully when only the pedal is pressed, I would assume the linkage would be able to achieve the condition seen in photo 2?

Doug.

[Wagon Sailor]

Originally Posted by packers1712

Do you reckon they are open far enough, it just seems odd that the linkage can't open them fully when only the pedal is pressed, I would assume the linkage would be able to achieve the condition seen in photo 2?

Doug.

I've had Solex carbs do the same thing due to a burr on a butterfly.

If they open further by hand, ie: when not connected to the linkage, then the linkage is probably at fault. If not, it may be that they're a bit skew or catching somehow and the bore is preventing them rotating fully.

[packers1712]

Just a quick update, yes Derek I have previously set up my carburettors using the SU how to guide and am happy that they are performing close to if not on the money as Volvo had intended, the car drives nicely and returns acceptable MPG.
Having made the previously mentioned adjustments to the rest point and linkage there is a noticeable difference in throttle response but probably nothing else so if I was sacrificing HP's by not managing to open the throttle fully before then my feeling based on the drive to the Ace Café last night is that it was immeasurable!
I'm happy that its as good as it can be so will make no further adjustments until the driveability suffers if at all.

Thanks for everyone's comments/suggestions and help they were invaluable and to echo Alan's comments from other threads within the forum what a valuable tool this place is for maintaining these sometimes fickle old motor vehicles!

Doug.

[Burdekin]

Excellent Doug. It's hard to tell from the pics but it looks like the lever that mounts on the manifold could go back more and someone has bent the stop forward. I might be dreaming but see attached pic of how it should be. With it straight there should be a 0.5mm gap between the stop and lever.

https://volvo1800pictures.com/docume...ne_B18_B_D.pdf

[Burdekin]

Also what distributor do you have and have you got vacuum to it?

[packers1712]

Originally Posted by Burdekin

Excellent Doug. It's hard to tell from the pics but it looks like the lever that mounts on the manifold could go back more and someone has bent the stop forward. I might be dreaming but see attached pic of how it should be. With it straight there should be a 0.5mm gap between the stop and lever.

https://volvo1800pictures.com/docume...ne_B18_B_D.pdf

You are exactly right and my adjustment included bending the stop back to parallel with the fixing point and then adjusting the rod to take out the slack.
I'm not sure that I've ended up with 0.5mm gap between the stop and linkage but I happy with the outcome!

Doug.