the vacuum advance basically needs to be disabled.  we dont use it in a boat.  if you just unhook the vacuum line, it could bounce around and move the timing around when you're driving.  and if you plug it with a cap, pressure builds inside that area from heat/cold and it'll move your timing around as well.  so you remove the vacuum advance and you basically put a plastic "plug" in its place to lock the timing at whatever its set at plus/minus the mechanical spring advance.



you're replacing this:



with this:



its fairly easy to do, just remove the cap and rotor, and then you might have to remove a couple screws to move the electrical board inside out of the way, undo a screw that holds the vacuum advance in, and then put the plastic lockout in its place (make sure to get the little advance arm into the hole in the lockout) and reassemble.



http://www.summitracing.com/parts/pro-67022c

$12

The MSD HEI instructions have the best information I've found so far.

http://static.summitracing.com/global/images/instructions/msd-8365_frm30256.pdf     MSD instructions

Happy reading 

So I've been trying to find markings to tell me what brand hei I have without pulling it out of the motor no where to be found took the cap and roter  off nothing not even a part # any suggestions


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It's probably an original GM HEI.  Most everything in the links I posted will work except the lock out bushings noted in the MSD instructions.

where can I find the vacuum advance lock and will it still wrk on a gm distributer and if the motor seems to be running good is it worth the trouble what am I loosing /or going to gain


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http://www.summitracing.com/parts/pro-67022c

http://www.summitracing.com/parts/dui-333333

There is a couple of lock outs/vacuum advance eliminators available through Summit Racing.

thanks


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