Your engine is a 229 and not a 231. Both are 3.8 and both were offered by GM at the same time, however there is a distinction. The 229 is actually based on the Chevy small block 305, where the 231 is a Buick design engine. They will use different vacuum diagrams.
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1988 9C1 - Modified LM1 @ 275HP/350TQ - TH700R4 - 3.08 8.5" Disc Rear - see it at
http://www.silicon212.org/9c1!
2005 Crown Vic P71 - former AZ DPS - 4.6 liters of pure creamy slothness!
1967 El Camino L79/M20 old school asphalt raper
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