BBYSTWY

For the less informed could you elaborate on the "MBT method"??

Thanks!!

MILD THUNDER

its really something that needs to be done on a dyno in a controlled enviroment.

Lets assume you are at 2500rpm. The piston is coming up the bore, and you light the spark at 18*btdc. The combustion event, may take place at say, 12* atdc , using all that energy from the explosion to force the piston down the bore, which then puts leverage on the crank. Thats what makes torque.

now, lets assume again you are at 2500rpm, but timing is at 34* btdc. Now combustion event may take place when the piston is at 0*, or even 2*btdc. This wants to force the piston backwards for a split second, resulting in torque loss, or even detonation.

and finally, at 2500, you may have timing at 4* btdc. Now Combustion event takes place at maybe 30* atdc, when the piston is further down the bore on its downstroke. Now you again have lost torque, because you wasted a bunch of energy that would have bee used to exert leverage on the crank. Also, with the retarded timing, the combustion mixture may not have fully burned , and then that gets pushed right out the exhaust valve. Raising the exhaust gas temperature.

Contrary to popular belief, you arent looking for max cylinder pressure. Your looking for max pressure over a longer time. You can make a very high cyl psi for a brief second with lots of timing, that wont do anything good for power, or safety. a dyno will tell you alot about how close you are to achieving your goal of getting the spark right. The problem is though, very fast sweep pulls most shops do, dont really give enough time for things to stabilize and gather data accurately when tuning for that. Also, things change with load as well as rpm. So what the engine wants at part throttle for timing, isnt the same as it would want at full throttle.

without spending some time on a dyno, my advice to start with, would be to follow mercurys timing tables for their carb supercharged engines for a baseline. Stay away from locked timing , or excessively retarded timing. Get a wideband installed, get your air fuel ratio in line, run a good ignition that will allow for a colder spark plug to be ran without fouling issues, keep the engine cool temp wise, and enjoy.

BBYSTWY

Sounds good that's the gameplan...thanks for the help!!