alecsammy

Hello,

I have a 502 mpi converted to a carb set with a voyager distrubor is the curve or set up different with a mpi vs. a carb engine. I would like to replace it with a thunderbolt ign. but I'm not sure the part numbers and what is needed , the engine will be alittle over 500hp . Do I only need the distributor or do I also need the control / spark module which is mounted seperate from the dist. Thanks

Noise Pollution

I've read in the selock repair manual that the ignition module in the distributor has 27* of advance built into it. So if you set your base timing at 8* that would give you 35* total. To se the base you have to put it service mode. I'm changing from the MPI to a carb set up, So we'll see.

Noise Pollution

I've talk to the guy that wrote this.


I recently swapped my MPI set-up for a Holley carb. So far, with more tuning needed, I have gained 200 rpm and 3.5 mph on top end. I have been asked to give a few tips on how to perform this swap. I will try and relay as much info as I can think of. Please feel free to ask any questions you may have.
I started by removing the ECU and all of the related wiring. I did have to snip a few wires that were tied into the main wiring harness. I just made sure that they were associated with the ECU and/or sensors before snipping. Most of this wiring simply just unplugs from the sensor and can be pulled from the harness. Be sure to leave any of the black wires attached, these are grounds. At least re-attach them to a good ground source on the engine. The knock sensors (2) can be left in the side of block or removed, as I did and plugged. The oil pressure unit down on the side of engine will be the one you will use to feed the gauge. The one below the distributor can be left in place, but no wire ran to it. I chose to use the MPI (Delco Voyager) distributor. It runs without the ECU by simply leaving the 4-wire connector unplugged. The remaining 2-wire connector runs from the distributor to the external ignition coil. Use the original harness (it can`t be plugged in wrong). To set the base timing on this distributor, you must "lock-out" the advance (which is provided by the ign module). To do this, you will need the 4-wire plug-in )that was originally used on the distributor) and a few inches of wire. Simply tie the two wires on the right together, snip off and discard the wire to the far left and connect an alligator clip and about 3 ft of wire to the remaining wire on the connector. To time, plug this connector into the un-used port on the distributor. Start engine and connect alligator clip to a 12 volt source. The idle will go down (the advance has been removed) and you can now set the base timing. When done, unplug connector and stow in toolbox.
Now back to conversion:

Griff

Since you are converted to a carb set up with around 500hp, I would use a TB IV system with a V8-HP module. It gives 20* of advance all in by 3000rpms and is the module used on the HP500. You could also just use a Crane Box and have several different curves to choose from.

alecsammy

I have used the voyager dist. with my conversion and want to change the distrubitor I'm not sure if the mpi uses a different set-up than the carb. I see that mercruiser uses a ignition and a spark control module for say a mer600 what are these modules used for and do I need them or just the distrubitor.

Griff

The Voyager is a GM HEI type distributor, right????? Is it not a marine distributor??? Is that why you're changing it???

You need a TB IV distributor and either an ignition module or Crane Ignition box and a coil. The ignition module or Crane Box will control the timing curve. There is no curve built into the TB distributors. The V8-HP ignition module would probably work best for combo, but could also use others like a V8-24.

Griff

This is what you need--for sale in the swap shop. The parts new are over $500 from Merc.

http://www.offshoreonly.com/forums/s...d.php?t=172809

alecsammy

do you have ran dom number or email Thanks

Griff

Reply to the thread in the swap shop and ask him. I don't know him. I just saw the ad.

You could also upgrade your membership. You will then be able to see all pics and send pm's to members.