This is what you can do with predator heads. This one is a 660. 5.125 strokes 4.53. I just dynoed this one again after damaging it about a year ago. The motor made more power before the repair NA because the chamber was smaller by 12 CCs. The motor is better for nitrous with the slower, larger chamber so I'll leave it as is. The damage came from using the junk che guides indy provided with the heads (I know better but didn't want to wait for real guides). The guides have but one saving grace. I dont think they'd ever grab a valve as long as you could beat it into the guide. The down side is they break with any real heat if you leave any part of them exposed in the exhaust. The result looks like a cigarette load expoded, all mushroomed out with frags going everywhere. I run 2.49 intakes, and shrank the exhaust down to about .04 between them in overlap. Losing control of the exhaust valve when it closed on a frag wacked the valves together and broke a spring. To fix it required sinking the valves and blending the camber back down to the valves giving me 12 more ccs. Taking compression from 14 to 13.

Chuck at best just did a smaller one that got over 1300 too so for anyone that wants to say it cant be done, tell chuck too lol. A max effort NA will make 1400 if you go after it properly. This sheet is with the larger chamber down close to 30 from the chamber increase. Also now requires 1.5 more degrees timing




Starting from scratch use a hemi block . The wedge requires plugs in the intake to access the inner valley bolts. Limits porting, and weakens the guide boss.