compression
 

if my engine made 640 horse on dyno at 6000 and 670 torque at 4600 with 100 grade fuel and small dome pistons makin 10.4 compression, and now we reduced duration by 20, centerline and tilt by 10, put in flat dome pistons making about 9.8 compression, on 93 fuel then how much approx hp loss could be expected?

Re: compression
 

Why dont you redyno it the tune up is very important in a marine engine and when you start to change valve timing and centerlines like that the carbs start to do things differently because of the signal the manifold sees is different take the time and redyno it it's to your advantage dont let the engine builder tell you otherwise I wouldn't want to leave a project like that half done for one of my customers. Good luck to you Sincerely Laz

Re: compression
 

thanks, so if im doing three engines i would need to dyno and tune all of em?