NNorton, I used the same set of 670 heads on both engines. Both were 400s, Both were .030 over. (Both with 4 speeds). The only difference was one used a 10.5 cc dome and one used a flat top and a different cam. On the 12 to 1 engine I ran a cam with adv lift of 467 adv duration of 313. The 10.75 engines cam was adv 458/ 292. The first engine had less in the way of street manners, especially in traffic. The booster I've been using (because its available in my small town) is 'HP plus super concentrated formula'. It says use the 12 oz bottle for up to 24 gallons. That's only half an oz per galion! Like I said, I use 1 oz to 1.5 gallons. Again, timing is the most important thing. Get as much advance as you can without a ping, then keep the fuel ratio the same. Octane alone does not make HP. I also try to keep the ponchos under 180 degrees. Stay cool man! Cme469
