Cruising Air fuel ratios.

[delcowizzid]

I logged my 5.7 Vortec with a 215/220 cam in it today. 55 mph @ 1,500 rpm with 13% throttle and 45-50 kpa on flat land. 70 mph @ 2,175 and 22% throttle at 45-55 kpa. Cruise timing was 32-39* btdc. 32* @ 1500 rpm and 39* @ 2,150. It wants more but distributor limitations prevent it. 41+ gives misfiring. Stock 0411 van tune only allows 35*BTDC.

how is the rotor phased you can probably get more in it if you clocked it round so its firing closer to the correct cylinder post in the cap

[Fast355]

how is the rotor phased you can probably get more in it if you clocked it round so its firing closer to the correct cylinder post in the cap

Its phased to spec of 0, it will throw a P1345 if i get it too far off.

[delcowizzid]

that is if you move the whole dizzy a tooth or clocked the case round and put the cam and crank triggers to far out of sync but if you move only the rotor on its shaft like an adjustable msd rotor it wont know its moved just the rotor will line up better at full timing and youll get more timing in the tune before you start sparking either to nowhere or to the previous distributer post in the firing order.if its phased with the rotor pointing directly at the post at TDC its going to be 20 degrees round from the post at 40 degrees advance.you can also do it with a rotor with a long outer edge and trim off either end of the contact to cover the post in a decient arc of movement but chop it short enough o stop it crossfiring to the next post

[Fast355]

that is if you move the whole dizzy a tooth or clocked the case round and put the cam and crank triggers to far out of sync but if you move only the rotor on its shaft like an adjustable msd rotor it wont know its moved just the rotor will line up better at full timing and youll get more timing in the tune before you start sparking either to nowhere or to the previous distributer post in the firing order.if its phased with the rotor pointing directly at the post at TDC its going to be 20 degrees round from the post at 40 degrees advance.you can also do it with a rotor with a long outer edge and trim off either end of the contact to cover the post in a decient arc of movement but chop it short enough o stop it crossfiring to the next post

Honestly its more trouble than I am looking to go into at the moment as the only time I pull those kind of numbers are steady speed, flat road, with no headwind, the only time it really needs much more than 39* of timing is downhill, overrun. When I put gears in it, I may look more into it. However my longer term plans are 24x or 58x and CNP ignition. Might also convert to DBW and someday a GM 6L80E.

[suffolkauto01]

you are syncing the rotor so spark happens at center or rotor you can not adjust timing like that the computer controls that set your timing sync the dis.