Slowbird-
Yes I have tested them on the track, as well as alot of dyno time with them on different combinations. I have seen as little as 10hp and 12 ft lbs. on small blocks, to double that on big blocks. We have tested on the track, with just bolting it on picked up a tenth and a half, and 2 miles an hour, making 4 back to back runs.. The big blocks like the 2" version. I have been messing with these for a while, and they do work on most applications. Some combinations require additional tuning. What I have seen on the dyno, looking at how the engine takes fuel and where it takes the fuel with the brake specifics, the signal is much stronger, and in the higher ranges, which shows the engine richens up. Now if the combination is lean, it works out of the box. I had to lean out the high speed air bleeds a few sizes to make up for it, but saw a huge gain in the midrange and top end, seeing the extra power. I would say call Summit or Jegs, or go to High Velocity Heads website. Bolt it on, but if you don't see a big improvement, some extra tuning may be rquired. That usually goes for any other spacer as well, since the spacer just aides in manifold tuning. But the HVH SS works. Hope this helps.Let me know if you have any questions.
Joe Pontiac
Maximum Race Engines
www.maximumraceengines.com
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