Greetings, I am wondering what the thoughts are on using a plenum turtle. I have a 500+ hp 383 sbc with a victor junior and brodix turtle jb welded into the plenum. I have never run the combination without it. I also made a tapered 4 hole space 1" thick phenolic material. Combo: 11.5 c.r. 383, 6" rod, 825 mighty demon, ported edelbrock heads with 2.05" intake valves, cam [email protected] .565"lift ex. [email protected] 050 .585" ex. The motor come on strong about 3000 rpm with a strong pull at 5000 lasting til 7000. But, I wonder if the turtle is just taking plenum space...