Hello, I have a hp ford 300 I6. It puts out the power of a 360 v8. For years I ran an MSD 6a analog box with an MSD street blaster TFI coil: https://www.summitracing.com/parts/msd-8227/overview/ I should mention that I use a DuraSpark2 distributor.

But the MSD died and I thought I'd try the Summit box. They had two choices. One was a bit less power, the other a bit more. I chose the second:
https://www.summitracing.com/parts/sum-850611/overview/

I have two questions:

1. Is that too hot a spark for 9.0:1 compression?

2. A Summit tech guy told me that this coil would work better: https://www.summitracing.com/parts/SUM-850500

I have a limited understanding of electronics, but although the peak current is higher, I notice the duration of spark is less, as is the turns ratio. Is it the resistance that makes it a better coil? Or was the tech just trying to sell me a coil?

*You know, my seat of the pants impression is that I'm not impressed with the Summit box. The MSD had more pep, more off the line power. The engine feels retarded. I'll have to ck the timing.

 

If you had a working system with the MSD box, the coil will work with the Summit box. He may just be recommending the solid state coil due to not knowing what you were running previously.

To answer your question, a low resistance coil with a high turns ratio will generally perform well. Most of the other ratings are witchcraft and can be doctored absed on how you measure them - eg peak voltage at the initial discharge or sustained average? Voltage output over what bridging gap and under what conditions? And so on.

Definitely check the timing. It may be that the Summit bow has retarded your timing slightly.

- boingk

 

Thanks for the note. I checked the timing. It was set at 8btc prior to install. Without touching the dizzy, it's now just off the edge of the scale. I believe that 16* btc. It acts retarded there, sluggish, wants more advance.

I had a lot of trouble telling the colors of the dizzy wires. When I hook it up as I believe it's supposed to be, according to the directions, it won't run unless I advance it 10*, and then it's way retarded.

 

Will it run properly with the wires reversed?

- boingk

 

I think you can see those wires once you remove the distributor cap, and they will be better preserved in there. I think you can see where they go too, so with some google searching for a good schematic diagram, or input from one of the wizards here, you can become sure of which wire really is which, exactly.

 

Thanks meangreen92, that was one of the first things I did. Even inside the cap the wires were very difficult to differentiate.

Boingk: No, it runs very poorly with the wires reversed.

I have come to suspect that Summit misinformed the public about which wire to cut to set this box up for a six or four cylinder. How else could simply installing the box cause a jump in timing from 8btdc to 18btdc?

 

That's it. I'm disappointed with the Summit box. It is a big step down in performance from the MSD 6A. I'll be shipping it back for a refund, and sending the MSD out to have it rebuilt.

Waste of time.

 

Wow, what a nightmare to speak to the MSD repairs dept. They go for lunch for an hour, and leave no message regarding that on their phone!! It was an absolute waste of time to deal with msd, with wait time of 20+ minutes.

After a two week wait they mailed back my old unit and said it could not be repaired.

So I tried the Summit 850611. I paid $50 more than the less expensive unit because I wanted to at least get performance equal to the MSD 6a I had. All the tech data showed this one put out a bit more than the msd; the less expensive one put out less than the 6a.

I tried the summit unit. The performance was a large step down from the MSD 6A. The summit tech said I needed to upgrade my coil. I spent another $57 on a summit 850615 cd coil.

Although I did feel an upgrade in performance, it is still a noticeable drop from the MSD 6A to the Summit unit. I am very disappointed.

 

Well, I hate to admit it, but I think I'll buy one of the digital MSD 6A's. I want to feel that power back that I had with old 6A. I've looked into the Jacob's ignition, and the Crane, but I know what I'll get with the MSD.