Sherrell
05-25-2011, 07:43 PM
THE SETUP:
Forte 351W, Roller Cam Engine – M12390F roller cam dist gear, M6250 E303 Cam, M6253A50 roller lifter kit, M6500-R302 roller lifters, Holley 670 Street Avenger Carb, Duraspark distributor (vacuum advance), MSD 6420 6AL control unit, MSD8869 converter cable.. (The engine was not run prior to me receiving it a couple of years ago as Mike's dyno broke at the time).
THE STORY:
I've 960 miles of light street driving on the car. Rarely above 4000 RPM. The car has been running rich and rough for some time. So this past weekend I finally decided to do something about it.
First I did the "country boy" timing job. I reset the timing by ear until the engine idled smoothly , transitioned smoothly with throttle modulation, hot-started consistently, and seemed happy. I drove it for 10-15 miles and all OK. Engine ran smooth at all speeds, accelerated smoothly, and didn't make any strange noises.
Then I decided to pull out my advance timing light and really tweek it. Shazam! The initial timing was 32 degrees. Tonight I checked the vacuum advance. The total advance is going over 50 degrees a 4000 RPM. For what it's worth, the engine will NOT idle with the initial advance set anywhere near 12 degrees.
THE QUESTION:
What the heck is going on? Can someone identify the likely causes of this behavior? Could this be explained by a distributor that had been installed a few degrees off? (I have not yet pulled the #1 plug to check TDC and distributor synchronization.)
A DISTRIBUTOR UPGRADE IN MY FUTURE?
Independent of understanding the source of the behavior I've described above, I'm thinking about ditching the Duraspark distributor and replacing it with an MSD distributor – since I already have the 6AL unit. I'm thinking either the MSD #8584 Billet distributor, the # 8578 Small Diameter Pro-Billet distributor, or the #8478 Street Pro-Billet. But I don't understand the distinctions well enough to have an informed view and there's a $100 price spread across the three, with the 8584 being the lease expensive and the 8478 being the most expensive. Anyone care to tutor me?
Thanks guys!
Sherrell
Forte 351W, Roller Cam Engine – M12390F roller cam dist gear, M6250 E303 Cam, M6253A50 roller lifter kit, M6500-R302 roller lifters, Holley 670 Street Avenger Carb, Duraspark distributor (vacuum advance), MSD 6420 6AL control unit, MSD8869 converter cable.. (The engine was not run prior to me receiving it a couple of years ago as Mike's dyno broke at the time).
THE STORY:
I've 960 miles of light street driving on the car. Rarely above 4000 RPM. The car has been running rich and rough for some time. So this past weekend I finally decided to do something about it.
First I did the "country boy" timing job. I reset the timing by ear until the engine idled smoothly , transitioned smoothly with throttle modulation, hot-started consistently, and seemed happy. I drove it for 10-15 miles and all OK. Engine ran smooth at all speeds, accelerated smoothly, and didn't make any strange noises.
Then I decided to pull out my advance timing light and really tweek it. Shazam! The initial timing was 32 degrees. Tonight I checked the vacuum advance. The total advance is going over 50 degrees a 4000 RPM. For what it's worth, the engine will NOT idle with the initial advance set anywhere near 12 degrees.
THE QUESTION:
What the heck is going on? Can someone identify the likely causes of this behavior? Could this be explained by a distributor that had been installed a few degrees off? (I have not yet pulled the #1 plug to check TDC and distributor synchronization.)
A DISTRIBUTOR UPGRADE IN MY FUTURE?
Independent of understanding the source of the behavior I've described above, I'm thinking about ditching the Duraspark distributor and replacing it with an MSD distributor – since I already have the 6AL unit. I'm thinking either the MSD #8584 Billet distributor, the # 8578 Small Diameter Pro-Billet distributor, or the #8478 Street Pro-Billet. But I don't understand the distinctions well enough to have an informed view and there's a $100 price spread across the three, with the 8584 being the lease expensive and the 8478 being the most expensive. Anyone care to tutor me?
Thanks guys!
Sherrell