Intake manifold differences - 748 vs 916/996

I know this is a long-shot, but anyone know what the differences are between the 748 intake manifolds and the 916/996/S4 manifolds?

748 part # 140.1.011.2A
996/S4 # 140.1.001.2A

I'm hoping the 996/S4 parts are thicker OD to allow for a smoother transition on the ID for the wider throttle bodies compared to the restricted t/b's ID on the 748's - but would be surprised if Duc went to the trouble to reduce the outer thickness of the 748 intakes??

Honestly, I don't think there's any difference.... But I could be wrong

I have a 996 and 748 motor and I held the two pieces up to each other and they have an exact same shape where the manifold meets the head. Sort of a figure eight cut out. Either part should work fine on either motor. The gaskets were the same also.

That's interesting! The 748's throttle bodies have the restricter (smaller ID) cast into their throttle bodies from the throttle valve all the way back to the manifold junction....so the ID of the t/b on the 748 must be smaller than the 916/996/S4 t/b at the manifold junction.

Now, the 748's smaller t/b ID is just about perfectly matched to the 748 intake manifold - there is no "lip" or "step" where the t/b meets the manifold.

So....if the intake manifolds have the SAME ID for both the 748 and the 916/996/S4, while the 916/996/S4 t/bodies are wider (without the restrictor cast into them), then I must assume that these bikes have a significant "lip" or "step" where the wider t/b's meet the intake manifolds?

Something doesn't seem right here....

i would expect the 748 manifolds are 44mm at the entry whereas the 916 ones are 46.5mm. apart from that they're the same. you can grind the rubber out as required too.

That makes more sense to me. I'll just get a set of 916/S4 manifolds to match the 748 throttle bodies after the restrictors are bored out....

Is the difference in the ID's of the t/bodies only 2.5MM? I thought the 916/S4 had a straight shot from the throttle plate without any restrictor-like narrowing of the venturi?

once you've priced new manifolds you might want to grind the 748 ones out.

$40 - used. I'm a cheapskate, so that works for me!