Bradness, you are correct. And damn! I forgot to measure the sided to side throttle blade diameter. Oh well.
Either way, the throttle blades were the exact same size from the svt to the 3.0.
The bore on both lower IM's tapers as you can see from the #'s. The butterfly valves are about halfway down so you can roughly guess the port diameter in the middle. I think it is about 33 mm. However you know that the butterflys are NOT perfectly round. They are designed to contact at an angle, so the mounting axis is the same size as the bore(~33mm) but the long side may be 34mm.
Here is what I did last weekend. I removed the butterflys and shafts and proceeded to widen out the primary and secondary ports by at 2-3mm on the primary and 1-2 on the secondary. I was matching them close to the gasket diameter. When I reassembled it yesterday, the butterflys still retained and angle, but there was a small gap on either side. They still operate normaly, but there is a little endplay now. If you are careful not to widen the middle of the bore to much, then the endplay is acceptable. That way you can get significant improvement in port diameter. The little gaps on the axis sides now will take the place of cracking the secondaries even though the secondaries are still closed. That is my HOPE at least.
Summary, (my two cents) widening the input side of the lower IM won't do any good since its already bigger than the middle or bottom. The taper already exists, probably to increase the velocity of the air as it enters the head. If you widen the ports, primary or secondary then you need to keep the taper in the bore, and you must widden the middle in order to make it effective. Then the upper manifold outlets must also be increased in diameter so that you aren't going from a restriction to a wide area then restriction again. And so on with the head ports. I just finished doing this to my intake system,when the heads come back I will widen the intakes similarly so that the new system is bigger overall than the older one, but has the same design intent.
ONe last thought, you could easily widen the sides of the bores that are perpendicular to the throttle blade shaft axis in order to gain an increase in area at that point and still have no endplay. I would have done it that way if I'f thought of it first :rolleyes:
Warmonger
