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GM 5.7L , SB350ci DISTRIBUTOR CONVERSION INFO NEEDED

POLECAT13

New member
GREETINGS!,

NEW GUY HERE. I HAVE A QUESTION REGARDING THE IGNITION SYSTEM IN MY BOAT. THE ENGINE IS A SB350ci CHEVROLET ENGINE. CURRENTLY IT HAS A MERC CRUISER THUNDERBOLT IGNITION SYSTEM IN IT. I HAVE BEEN PLAGUED WITH PROBLEMS WITH IT ALL SUMMER AND IT'S GETTING EXPENSIVE BUYING REPLACEMENT PARTS FOR THE THUNDERBOLT IGNITION SYSTEM . I'M WONDERING IF I CAN JUST CHANGE THE DISTRIBUTOR IN IT FROM THE THUNDERBOLT SYSTEM TO A STANDARD GM HEI
(BIG CAP HEI W/ COIL IN THE CAP)DISTRIBUTOR THAT HAS A VACUUM ADVANCE RATHER THAN AN ELECTRONICALLY CONTROLLED ADVANCE SYSTEM? IS THIS POSSIBLE? IS THERE A CONVERSION PROCEDURE OR A KIT FOR DOING THIS OR IS IT NOT A GOOD IDEA? I APPRECIATE ANY AND ALL ADVICE & INFO ANYONE CAN GIVE ME. :cool:
 
Do not use an automotive vacuum advance distributor!

If you prefer to get away from EST, look at the Mallory YLM624AV, or one of the many other options.



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Ok. Just for the sake of knowledge, may I ask why?

Yes you may.

1...... the automotive ignition distributor is not "ignition source protected". In other words, there is nothing to prevent an escaping internal spark from igniting gasoline vapors.

2...... the advance curve is incorrect for Marine Engine use and may cause engine damage. I.E., ignition induced Detonation, especially with the GM Full Dished piston build.

3...... t
he marine engine is always under load, so there is no minimum throttle position that makes for manifold pressure that could take advantage of vacuum advance.
It is a fuel economy device for the automotive engine.



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