SureStart engines with cracked backplate housings

Because of the small amount of false air entering the venturi through the cracks, instead of the throttle tube, it may affect the throttle efficiency (even when the throttle is fully closed, the engine can inhale some air, and may idle instead of stopping..but conventional COX heads are not hot enough to keep a good idle without flame-out, anyway, unless you use hot glow plug in a plug adaptor, and/or retain some heat with an exhaust manifold) .

Other than the risk of getting the spray bar rotated if the NV is over tightened, there is no more risk I could see...this is an inherent problem of almost all SureStarts with the grey horseshoe backplate. I also have a few with the same cracks. In another post  someone mentioned, the material of the grey backplate is not the same flexible delrin as was used for earlier production backplates, but a more brittle material,  therefore the venturi snapped when the spraybar was pushed in in the factory.

I am not sure if there is a reliable glue that would stay in the crack and keep the edges together, especially in a nitro environment. The good thing is that the throttle tube has a lip that slips over the venturi intake, and lends a bit of circular/tangential strength to it that may at least prevent the crack to advance further.