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I was digging around in my Opel stuff and came across this '75 fuelie exhaust manifold I forgot I had. (I'm discovering all sorts of stuff I haven't looked at in years. It's sort of like Christmas!)

With all the discussions of "Sprint" exhaust manifolds on here I thought it might be helpful to show a comparison of the '75 USA spec exhaust manifold and a later Euro version that I have from my Ascona B rally car. The Euro manifold I have was from my Group A engine and it has been ported out at both the inlet and outlet. My '75 USA Sprint is stock except the lug has been ground off the center branch.

Euro manifold on top, USA on bottom. Note the wider collector on the Euro manifold. The rest is identical.

 

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Closeup of the outlets. Euro on the left, USA on the right. The Euro collector is wider on the horizontal but both are the same on the vertical. The Euro manifold has larger outlet holes stock plus this manifold has been ported out to match the gasket.

 

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This picture illustrates how much bigger the holes are in the Euro manifold. Here the Euro outlet gasket is taped to the USA maniflod.

 

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A comparison of the inlet ports. Euro manifold on top. You can see how extensive the porting is here.

 

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Another illustration of how much porting was done. Here the Euro gasket is placed on the USA manifold. This gasket actually had to have the holes enlarged to match the ported head and manifolds.

 

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This shows how the Euro manifold is matched to the gasket (or vice-versa.)

 

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Here we have the modified Euro gasket stacked on top of a stock Opel metal gasket stacked on top of the '75 USA manifold. You can see the different size differences and how even porting to the stock gasket would make a big difference. You can also see how much porting was done to the intakes. I have a set of Irmscher intake manifolds that have an incredible amount of porting done to them.