Bob is correct all engines respond different to spacers. You almost have to bring a few spacers with you to the track and try them. I ran a HVH Super Sucker & it made no difference at all. I use a Birchwood spacer now, and it benefits me in just keeping the carburetor isolated from the intake manifolds heat.
I ordered a wood one from Summit a couple of weeks ago. It's a 1" open and came with gaskets studs and nuts. I think if your intake is open you use the open spacer. I went with the wood because like Dave said, it, supossed to keep the heat off the carb.
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!