74Scooter, do you know the O.D. of the holes in your 7576 pictured here? I measured the hole(s) in mine and they are 0.469" diameter. The diameter of the 3/8"-16 x 1-1/2" hex head bolts that I have measure 0.369" at the O.D. of the threads. So the holes on my intake are exactly 0.100" larger than the bolts giving not quite 1/16" clearance all around the bolt. I was able to drop these hex head bolts that I mention here right down into the holes and the threads never got close to the sides of the holes and bolt heads barely touched the intake runner, including the hole they milled down. If they hadn't milled it down, I believe the 1-1/2" length bolt would have still went right into the hole. Wonder if the holes in your manifold are smaller diameter than on mine by the looks of the angle of those small round head bolts you are showing. I did measure several of the holes on the intake and they were all within a 0.001" or two of the 0.469", so they didn't just make the hole the milled down a larger diameter.
Another thing I noticed was that the pad at the top of the holes were not cast parallel with the surface that mates up to the head. The pads on mine are thinner at the edge of the manifold and get thicker as you move in toward the valley? Does this mean that the holes in the heads aren't exactly drilled perpendicular to the mating surface of the head but are at a slight angle? I pulled a bolt out of the stock intake manifold on the engine and the pad mating surface on the top of the intake looks to be parallel with the intake mating surface and the bolt hole in the intake runs parallel with the hole in the stock head. At least it appears that way. If all contact surfaces are not parallel with each other and the threaded hole in the heads are not exactly perpendicular to those planes in space wouldn't you get an uneven torque load distribution on the bolts, washers, intake and head. Thanks
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