Finally! The ZZ3 sits happily in it's new habitat. Now comes the fun part! Will the headers fit?
I originally considered ordering the custom Astro headers from Custom Conversions for around $315. These headers are made by Sanderson, and actually turned out to be a cross between left and right headers from two other vehicle applications. I got the price down to $200 with my connections to Sanderson Headers, but the biggest problem was the small primary tube size (1.5 inch) and the small collector size (2.5"). This is fine for a typical TPI V8 install but for a 430+ hp 350 I felt the primary tube size was too restrictive. That's when my friend advised me that the subframe of the Astro is essentially a modified 2nd Generation F-Body subframe. A few eyeball measurements and a trip to the local speed shop proved our theory!! A $91 set of Hedman #68600 headers bolt right on to the V8 Astro install! No modifications, three inch collectors and 1 3/4" primaries! A small notch must be cut into the V8 adapter mount (see red arrow, cut along green dots) on the driver side. You can easily install the engine and header to mark the area to be removed.. then remove the header (not even the spark plugs have to be removed!) and support the engine.. unbolt the mount and make the cut.. slide the mount back in, bolt it back in place and you're done! Simple.
The next step was removing the TBI/ECM wiring from the main harness. Two plugs on the passenger side of the fire wall (the ecm actually goes through the wall then plugs in to the ECM unit) make all connections to the engine. The AC wiring is seperate, as is the cruise control harness. Unlike other 80's GM applications, the ECM wiring is integrated into the main engine electrical (gauges mostly) harness. You must remove all wire looms/tape and wires. About 15 cuts need to be made between the ECM and main electical harness plug. I used heat shrink tubing to cap each of these wires. I extended the torque converter lockup wire (for manual tq lockup switch, added a tachometer wire and - -get this -- the passenger side door "light switch" actually runs through the ECM harness!! So you need to locate this wire and extend it, then run it back through the van ECM wire harness firewall hole before sealing it. Don't forget to cut the power feed to the in-tank fuel pump or BOOM when you remove the pump.
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