SPICA Intake Manifold Porting - Alfa Romeo Bulletin Board & Forums
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post #1 of 3 (permalink) Old 06-08-2019, 08:54 PM Thread Starter
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SPICA Intake Manifold Porting

Does Anyone Have Experience With Porting SPICA Intake Manifolds? I'm Replacing The Intake Manifold On A 1973 Spider. The Motor Is Completely Stock Although I have The Following Camshafts I Can Play Around With: A 10502 cam, A Pair Of 10548 Cams, A Motronic S4 Exhaust Cam, And A Pair Of RJR Cams (probably a bit much for this motor). I'm Planning On Using One Of The 10548 Cams For The Intake And The Motronic S4 Cam For The Exhaust. As A Matter Of Course I'm Cleaning Up The Intake Manifold And Removing The Casting Marks On The Intake Ports (I've ported numerous carb'ed manifolds in the past so I've gotten somewhat proficient at it). Are There Any Spec's For Porting This Manifold That Make Any Worthwhile Improvements?

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post #2 of 3 (permalink) Old 06-09-2019, 06:55 AM
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Wes Ingram used to offer manifolds with larger butterflies, but this has been gone from his website for some years. Jim Steck enlarged the bores on my SPICA throttle bodies some years ago, but retained the stock butterflies. I installed these along with some other modifications so was not able to identify any improvement.

Way back in the day people used to "knife edge" butterflies in SU carburetors and file down the attachment screws. I obtained a spare set of throttle bodies to do this, but the project has become dormant.

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George Schweikle

1976 Spider (Dedicated Autocrosser, "SPICA, No Carbs")
1991 Spider Veloce (Retirement cruiser)
Scuderia Non Originale
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post #3 of 3 (permalink) Old 06-09-2019, 09:32 AM
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Don't enlarge them. just clean them up and match them to the head. My Jim Steck prepared head & manifold has a small step down from the manifold to the head on the bottom of the port.

Ed Prytherch
79 Spider
85 GTV6 3L
76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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