Misc: Carburettors 276 Slide Dimensions

[LoneStar]

Hello all,

My Rapide project has standard Amal 276 carbs. I'm trying to determine if there's unacceptable wear in the carb bodies, the slides or both. Also, oversize slides are available - will these fit? To that end, does anyone know the unworn dimensions for

• slide diameter
• slide bore diameter

or, failing those, what is the acceptable limit for clearance between the slide and bore?

Thanks,

 

[chankly bore]

This might not help much, but slides wear down towards the bottom, mostly on the inlet side. The bodies wear as well. Usual solution is re-sleeving the bodies with new slides fitted, or new instruments altogether. If you lift the slide a quarter inch and you can hear it rattle then you need to sort it in my opinion, because it will be leaning off your mixture. You should get a rough idea of the new slide diameter up near the top, as not much wear should happen there. I've never heard of oversize slides.

 

[Robert Watson]

On these carbs, the slides actually have grooves that run on tracks raised on the sides of the jet blocks. Look at your jet blocks in this area and you will likely see the wear quite significantly there. If you are talented you can make new jet blocks, resleeve the bores and put in standard new slides, or just dial

1 800 send me two new carbs!

 

[Magnetoman]

what is the acceptable limit for clearance between the slide and bore?

The official answer is the clearance should be 0.004". Less than that and you risk having the slide seize at an inopportune time, and greater than that it will rattle around enough to affect the mixture in an uncontrolled way.

The photograph shows the situation in progress when I sleeved the bore of a "rare" Monobloc used only on 1957 BSA Spitfire Scramblers. Clearance is read CCW on the gauge since the bore is larger than that of the slide used to set the '0'. As can be seen, I overshot by 0.0002" when I bored the sleeve.