Automotive CDI for older 4 cyl Merc

[RogerH]

I want to try to retrofit the Keik. Mag with a small MSD distributor and run a MSD CDI box (like a 6A) and one of their Blaster coils on a 30H or 55H. The challenge is in fitting the distributor to the Mag tower and coupling the shaft. With that solved I have the following question.

What spark plugs should we test on such a setup??? The MSD box requires spiral wound spark plug wires to avoid EMI problems with the box. There are good low ohmage wires of this type available.

After this, I will be looking into a Distributorless Ignition System (DIS). This will require a flywheel pickup to trigger the DIS box. Wayne Taylor has already developed these for various applications. The DIS systems are expensive but provide about any timing capability desired.

Comments on aftermarket ignition systems and your experience with them would be welcomed.
Thanks,
Roger Hinsdale

[mercguy]

800/850 setup

I want to try to retrofit the Keik. Mag with a small MSD distributor and run a MSD CDI box (like a 6A) and one of their Blaster coils on a 30H or 55H. The challenge is in fitting the distributor to the Mag tower and coupling the shaft. With that solved I have the following question.

What spark plugs should we test on such a setup??? The MSD box requires spiral wound spark plug wires to avoid EMI problems with the box. There are good low ohmage wires of this type available.

After this, I will be looking into a Distributorless Ignition System (DIS). This will require a flywheel pickup to trigger the DIS box. Wayne Taylor has already developed these for various applications. The DIS systems are expensive but provide about any timing capability desired.

Comments on aftermarket ignition systems and your experience with them would be welcomed.
Thanks,
Roger Hinsdale

Roger, if you want to use a battery ignition distributor type setup, it would be much easier to just use the Merc 800/850 type distributor setup, along with the RAPAIR coil/switchbox assy..............it is just as good, if not better than the MSD setup you are talking about.

[sam]

Steve Roskowski is already making this:

[RogerH]

Daren & Sam,
Thanks for your comments. I was wondering what models of the Merc's distributors I should be looking at. I happened to get a Merc 650 (4cyl) and that definitely isn't the one!!! Is the 800/850 a magnetic trigger type?
Sam, I had heard of Roskowski's ignition and plan to use it on a "444 Project" motor with Tim Krutz. Thanks for the picture as it clarifies a lot. I knew he was using chainsaw parts and his system looks really great. I understand you can advance the entire plate under way much like advancing a distributor. This would make the system quite tunable and its certainly simple. No battery!!!
I was shocked at the asking price of the chain saw coils. I priced Husqvarna's that list around $80. The flywheel was just a bit less. Would need to find a "friendly" dealer.

Thanks again for your comments.
Roger

[mercguy]

Daren & Sam,
Thanks for your comments. I was wondering what models of the Merc's distributors I should be looking at. I happened to get a Merc 650 (4cyl) and that definitely isn't the one!!! Is the 800/850 a magnetic trigger type?
Sam, I had heard of Roskowski's ignition and plan to use it on a "444 Project" motor with Tim Krutz. Thanks for the picture as it clarifies a lot. I knew he was using chainsaw parts and his system looks really great. I understand you can advance the entire plate under way much like advancing a distributor. This would make the system quite tunable and its certainly simple. No battery!!!
I was shocked at the asking price of the chain saw coils. I priced Husqvarna's that list around $80. The flywheel was just a bit less. Would need to find a "friendly" dealer.

Thanks again for your comments.
Roger

Roger, the 1969-1976 800/850 4cyl's have the battery ignition belt driven distributor that works quite well. The Fuschlin's make up a trick MSD distributor setup also, like you are thinking of doing. I was gonna go the Roskowski route for the ignition system on my C Merc, but since I have the 800/850 stuff in my parts supply, I am gonna go that route (and remove my current Merc 4D mag setup, which actually has not given me any problems, even up to 9000rpm's........).

[RogerH]

Roger, the 1969-1976 800/850 4cyl's have the battery ignition belt driven distributor that works quite well. The Fuschlin's make up a trick MSD distributor setup also, like you are thinking of doing. I was gonna go the Roskowski route for the ignition system on my C Merc, but since I have the 800/850 stuff in my parts supply, I am gonna go that route (and remove my current Merc 4D mag setup, which actually has not given me any problems, even up to 9000rpm's........).

Daren,
I'd like to talk with the Fuschlin's. Can you give me some contact information. I'm concerned about the advance mechanism within the MSD unit, as I will be turning it backwards. Will probably have to lock the MSD and use the Mag Tower advance only. Didn't want to do that. How hard is it to find the 800/850 distributors?

[Joe J]

Paul Fuchslin is a member here, his user name is Alky6.

Joe Johnson

[mercguy]

Ebay

Daren,
I'd like to talk with the Fuschlin's. Can you give me some contact information. I'm concerned about the advance mechanism within the MSD unit, as I will be turning it backwards. Will probably have to lock the MSD and use the Mag Tower advance only. Didn't want to do that. How hard is it to find the 800/850 distributors?

the 800/850 distributors pop up all the time on Ebay, along with switchboxes and coils. But, what I do is just use the rotor assy and cap from the stock unit and replace the rest of the parts with a RAPAIR/CDI conversion kit (around $400). The only drawback with the RAPAIR SETUP is that is does not have a tach circuit, but you can use an automotive Autometer tach with the setup.

[sam]

By chance or luck I haven't come across a bad Merc distributor, I just use the Rapair/CDI replacement switchbox-coil assembly - racer's net price from Seaway $150. I was using Merc switch boxes until I discovered that although they "worked" and made spark, they don't work "like new"

With the new switch boxes I get quicker starting and use about half as much choke time .... and no breaking up or hesitation at 45,000+ sparks per minute, plus they use less battery power.

I don't know how small a battery you can use, but the battery for ignition only could be pretty small. I use a 13 pound Odyssey PC-680 for starting (about 12-16 starts of a padded 6 cylinder between charges). The 6 pound PC-310 would probably run the ignition alone on a 4 cylinder for at least a season of racing without recharging.

[RogerH]

It sure seems like a Merc distributor and Rapair Kit is the way to go. Sam, I also appreciate the Odyssey battery information. Regards - Roger

[deverhart1]

Merc distributor

I made my own distributor using the Merc tower housing but making my own shaft. I needed to also make a plate to mount a cap and rotor on. I made two different styles. I made one using points and one using a magnet pickup. I like the points better as the timing is checkable with a buzz box or a test light. The magnet pickup has to be checked with a timing light, very inconvienent at a race in the sun light. I used a Ford Ranger cap, rotor, and the points were extra heavy duty Ford. I have ran the system for 4 seasons with no problems caused by the system. There were some operator errors as it is VERY IMPORTANT to maintain proper polarity with the MSD module. It smokes immediately if you hook the wrong terminals to the battery.
David Everhart S52