I run the Holley HP EFI system in my na 540s - multiport injection. I went from msd ignitions with pro billet distributors (magnetic pickups) to disconnecting the mag pickup and used the Holley 60-2 crank trigger.

It's a hall effect trigger, far less interference issues than the magnetic field from the msd, less issues with EFI and a lot more accurate (typical of any crank trigger). Holley EFI lets you run paired, bank to bank, or un-timed sequential injection strategy like this or you can install a cam sync to go full sequential. Without the cam sync, the ECM doesn't know what stroke the engine is on (2 turns of the crank for every turn of the cam). Ideally a hall effect cam sync should be used, but some have modified the reluctor wheel down to one blade in the MSD distributor and reuse the MSD mag pickup. Either signal can be input into the Holley ECM to handle the signal. Again, the magnetic pickup route is asking for interference issues.

I basically ran one season with the MSD ignitions being controlled by the Holley ECM to get full timing control. This worked well, but was still only as reliable as the MSD ignition box (I've gone through 4 in 6 years). After being sick of the MSD system after another failure, I was recommended to switch to Holley DIS. Although it makes more sense for supercharged engines for some of the reasons already brought up above, I still decided to make the switch with my NA engines since I already had the crank trigger and really only had to invest in the coils and wire harness.

The result - Wow, the engines idle better, my oil looks cleaner, and best of all, no more MSD box or components. I know a lot of guys have been using DIS in big cubic inch daily drivers on the car/truck side, so I'm hoping that with fully potted coils that the DIS system lasts a long time on my boat engines. The DIS concept certainly removes all the moving parts from the spark distribution side of things, and separate coils allow for more spark energy since the coils can charge up while the other cylinders fire. The ability to customize timing is not something I've needed to do (my engines run pretty even bank to bank), but the control is there if I ever wanted it, or added superchargers.

FWIW Crane Cams just came out with some new ignition components including a brand new crank trigger pickup sensor. I did not get all the jist but some of it. Some of the features are operating voltage at 6 - 24 VDC and a range to 12,000 RPM, Static timing LED light for accurate set up and the sensor providing absolute stable timing , Part # for this is 1000-2100

Cost me about 11k to upgrade mine. Engines needed to come out, new wiring harnesses, crank trigger wheel caused alingnment issue with all the other pulleys, so they had to be milled. Along with brackets for coils, new wires. No more MSD boxes but did blow one crank position sensor at 110 once. Replaced with part from local gm dealer.

WOW 11k!

I was fortunate in that I had plenty of room in my engine compartment to mount all the pulley brackets outward the thickness of the crank trigger wheel. Probably not so easy with superchargers involved.

I ended up putting my coil packs between the throttle body and valve cover, with the HP EFI ECM on the opposite side. I looked at putting them on the back of the engine, but my high capacity oil coolers are there. By doing this, I was able to shorten half of the plug wires considerably. The ECM wire harnesses easily avoided all of the sources of dirty power/noise lower on the engine (battery cables, spark plugs, etc...).

I made the brackets and used PEM nuts (self-clinching) for the coils so that I can remove them quickly with a screw driver without dealing with the nuts.

Damn good looking engines!

I wanted to go crank trigger as well, but with the procharger and sepentine belt set up and no room in the front of the engine decided to shelve the idea to later...

you know you can mill the balancer snout the distance the trigger wheel is thick,,no alignment problems then.balancer movers in a little,thats all.

^^^ yep, 1/8" for the Holley trigger wheel, 5/16 for msd

We normally just take it out of the accessory pulley. This one had quite a different setup. The water pumps were mounted on the outsides of each engine, meaning one was on the opposite side of where it normally is. Because the pump alignment wasn't the same, it had a strange pulley setup. We ended up taking it out of the balancer. With the pump moved, our normal crank trigger brackets wouldn't work. We had to do them individually. Combine that with very little room to work with, and it was a tough one. It normally isn't nearly that much. We had to pull the engines, remove all of the wiring and start over from scratch. Since we never planned for the coils to be on the engines, we didn't really leave room for them. We had to move a lot of stuff around to make it all work.

When building an engine from scratch, it adds less than 2K to the price.....and it's well worth it. Pretty much every sc engine that leaves here has DIS. I got tired of MSD boxes failing, distributors rusting up, etc. We built all of the brackets and mounts our self, but there may be stuff available now. We still have our trigger wheels and cam sensors made.

Here are some pics of the components.