This thing! What is this? I had the exact same, identical in every way thing sticking out from that same hole on my '94 Fleetwood. ..... maybe it originally had a spacer between it and the manifold, ...... Strange though, no real reason that I can think of to use a spacer back there.
The premise for those cast spacers is to allow lateral slip as the cast manifolds heat up and permit expansion without cracking from stress. I noticed as you that the protruding amount on mine was the same length as a spacer and realized the bolt snapped right at the head. Those spacers go on all bolts except the 2 centerboard locations each bank, though I've NEVER heard of cyl. 1 and 2 bolts breaking.
The only question I have is why spacers became a "thing" with this motor. I've seen maybe the same rough cast iron type regular washers on some motors, but certainly not the tall ones as on an LT-. I don't recall them on prior SBC and other old cars. Perhaps cheaper more crack-prone pot metal used in the manifolds? Or "improved" flow with increased lever arm thermo somethings in the oem design causing way more stress? All I know is be sure to use all those cast iron spacers per original placement, and don't over-tighten the bolts. It should have been a TSB way back when.
EDIT: Pic of said layout for ref
\'96SS SOB: SSRI, Herter Tune, Tri-Y II, SLP SS, 3000 Edge, F/HO bars, METCO extendeds and CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear)
\'96FWB BUW-Butt Ugly White: SS Bars, METCO LCAs, Koni Reds, PowerTrax No-Slip
Last edited by 96 Black; 01-06-2017 at 10:17 AM.