My pump gas Duster gained a little over.2 ET and 4 mph by swapping from a set of ported big valve 906 heads that flowed 266 CFM at .600 lift to a set of CNC ported Eddy RPM that flowed 310 CFM at .600 on the same bench by the same tech Both sets of heads had the exact same size combustion chambers so the compression ratio stayed the same I change the crankshaft stroke by .050(4.250 to 4.300 ) to raise the pistons up the next winter, went from 9.25 to 1 to 10.29 to 1 and the car picked up another .18 ET and .5 MPH the car did have a fuel delivery problem back then, it picked up a tiny bit more when I corrected that, fuel filter between the fuel pump and fuel tank was a 10 micron element It was restricting the fuel inlet side of the pump so it would run out of fuel slowly the last 500 Ft in the 1/4 I couldn't fatten the jetting up enough to slow the car MPH down in the 1/4 mile , once I swapped that filter out to a 80 micron unit the car slowed down with the bigger jets I was close to perfect on the six pak jetting the first time so it ended up being jetted back down there BTW, I ended up swapping the ported Eddy RPM to a set of Indy M.W. port size SR heads (that flowed 30 CFM more than the Eddy heads did) with the Indy matching Dominator intake and carb. and the dang car became to fast for the tech. officials, 9.94 ET at 134,8 MPH It is legal to run ten flat That car has been very fun to build and drive, now its time for a new one that is built to go faster legally so I can learn some more about chassis tuning