Several weeks back I had ordered a 91-94 intake that I planned on converting to TBI and using. The only plugs/set screws I could find that were beyond 1/2" were 5/8, 3/8" pipe thread tap is the same thread as the 5/8" set screw but you can see here that I ran the drill bit too deep and destroyed the intake-
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The second one I ordered arrived yesterday, you can see that even though they fit the same years that they are different castings, the one in the rear is more suited for an adapter plate. Plus there were two casting flaws in the first intake anyway, worked out well in the end-
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I ended up using 9/16x18 set screws, this way I did not have to drill out the injector holes. 9/16x18 are damn near impossible to find and when you do they are expensive. A bottom tap was not available to me so I bought a taper tap and a plug tap, the plug tap I cut down to a bottom tap, worked out perfect-
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