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Looks like the 3858180* did have some built in Tonawanda. @GUSTO14@Powershift Does this change your view that this could be a 65 and not a 66?
Oh well... casting on intake Manifold: 3872783 GM1 - 1966 Cast Iron 300HP 327.
no the suffix code is crystal clear on what car it started life in. They built a lot of 66 full size cars. That engine was very popular That intake was used on other Chevy small blocks
Other forum members have sorted out your numbers question. I envy you having a nice looking running drivable and all together Corvette. I noticed some small detail items you may want to address down the road, nothing serious. Although the factory did use short sections of rubber line on the 365-horse engine in 64-65 I have never liked the idea of a rubber fuel line so you may want to change to a hard metal line, a choice to make or not make in the future. The vacuum advance should be full time and not ported, ported meaning no vacuum at idle. If you post the numbers off the carburetor air horn someone can probably tell you if the vacuum port used for the vacuum advance is ported or not. If the car runs fine and does not overheat, I would not worry about it. Last item would be the crankcase ventilation. The manifold oil fill is using a breather cap which was discontinued after 1962 and the PCV routing has been changed. Starting in 1963 the crankcase vent went to a closed design, so you may want to look at the venting system to make sure it is working as it should and also not drawing unfiltered air in through the oil fill tube.
