Engine milling maths
Sounds like some idiot already ruined (or made it to only fit one combination) one of the intakes, and your customer didn't know it. For a street engine, with used iron heads, I always mill the heads to get a flat surface.
Can you read? He ordered BOTH at the same time, from the same place and they came together. Both were brand new.
WTF? Do you not understand there is a tolerance for intake manifold width like everything else?
They grab the castings and machine off enough to get a flat, clean surface and it’s done.
You can take 10 intake manifolds exactly a like and you may have 2 or 3 that will fit and 7 that won’t.
It’s no different that when the factory mills a head decks and manifold faces. They have a spec they have to make. If it cleans up on the high side they send it. If it takes milling until it hits the low side, they do it. If it goes under, they set them aside and find a use for them later.
That’s why looking at a blueprint you see the NOMINAL deck height. Whatever it is...say 9.600 but that doesn’t mean that’s what it comes off the mill at. My X block was .040 or so over that. I’ve seen some blocks that were .050 under nominal. It depends on the casting.
Just like heads. The chambers have a nominal volume. Most are way bigger that that, because when the heads come though the mill, they only mill enough off to clean up the castings.
This **** isn’t complicated. It’s just a fact of building engines. I don't know a single machinist who mills the heads. Not one. They all know better.
