Question on Ignition Set Up.

[SHO-Z]

I have a 260Z with 280 engine. The ignition set up is stock 260z. I am planning on supercharging @ around 10 to 12 psi of boost and with forced induction on triple SK racing carbs. I have been looking at an MSD unit for spark retard under boost. Is the vacume advance on the distrubutor still hooked up like normal or should I disconnect it? Any input on how to modify my current set up would be appreciated.

[Z Driver]

I have the MSD 6BTM. I haven't installed it yet but I have looked in the manual. There is no mention of disconnecting the vaccum, but the manual is not specific to the 6BTM, it covers all the 6 series MSD products. I'm sure there are some on here that have actual experience with this and can help you.

[randy 77zt]

when it goes on boost it wont have vacuem-so that drops out of total advance.initial+vacuem+centrifigual=total advance.total should be set up about 36btdc for highway cruise speeds.best dizzy for msd box is 75-78 280.it has a magnetic pick up.connect to mag pick-up wires on msd box directly.if you get a used dizzy make sure to vacuem test the advance diaphram and test the centrifigual advance on the motor with a dial advance test timing light.if you disconnect the vacuem line run up the engine and check for centrifigual at about 300 rpm.it should read more than initial and you should see it advance.to set msd 6btl run engine up to 3000 or where to centrifigual is done.disconnct vacuem advance.put a hand pressure pump on msd vacuem line .pump it up to your max boost.timing should retard to 20-24 btdc.if you chip the sealer away from dizzy vacuem can you will find an adjustment screw.you might be able to build a dizzy that will work.read up on distributor tuning theory.when my 77 had original motor i used 2 dizzy to build 1 good 1 with the advance curve that i wanted.the original advance curves were set for emissions-not performance.

[Guest bastaad525]

I've heard a few people mention that the boost can actually damage the vacuum advance canister on the stock N/A distributors, I think it's common practice for people running N/A dizzies on forced induction to disconnect the vac advance.