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post #1 of (permalink) Old 01-16-2004, 10:36 PM Thread Starter
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How to: GM Duraspark ignitions in parallel for TBI

EDIT: I edited the title on this post so that it would better reflect the end content.

For those of you with the Howell TBI and MSD. I need part from your wiring harness. This is a small circuit board that is located near the ECM in the harness. This part would be replaced by the Howell tach filter for an MSD. If for some reason you happen to have the original board after installing an MSD I really need that part.

Thanks,
Tom
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post #2 of (permalink) Old 01-16-2004, 11:05 PM
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Re: Anyone install an MSD on their Howell TBI??

1. Tom, I'm confused...
2. Are you needing the Tach filter
3. Used on a Howell with the MSD system?
4. It's a special add-on sold,
5. By Howell to customers with a MSD.
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post #3 of (permalink) Old 01-17-2004, 12:03 AM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Hey LEVE,

No need for confusion. I actually need the tach filter that comes standard in the harness. This is the filter that gets replaced by the MSD filter supplied by Howell. I was just hoping someone had one laying around.

Later,
Tom
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post #4 of (permalink) Old 01-17-2004, 12:20 AM
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Re: Anyone install an MSD on their Howell TBI??

1. Tom, it ain't standard,
2. Unless you tell Howell when you order the kit,
3. That you need one.
4. In searching the posts,
5. TR mentioned that MSD sells 'em,
6. For a whole lot less than Howell.
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post #5 of (permalink) Old 01-17-2004, 01:13 AM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Hey LEVE,

Maybe I have been unclear. All Howell TBI systems have a tach signal filter. The standard filter is designed to work with most basic ignition systems that provide a tach signal from the coil (-). MSD and other aftermarket ignition systems provide a different type of spark and also a different tach signal. Howell has a replacement tach filter that you install if you replace your stock ignition with an MSD type ignition. The replacement filter takes the place of the original filter. The exception would be if you told Howell that you had an MSD when you placed your order. In that case they would include the proper MSD filter in your harness to begin with. I am looking for a standard filter from someone that has added an MSD to their Howell TBI and replaced the original filter with the Howell MSD filter.

Clear as mud.....

Later,

PS I may have found a way around this. I will post a follow up Sunday.
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post #6 of (permalink) Old 01-17-2004, 11:51 AM
 
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Re: Anyone install an MSD on their Howell TBI??

dude,
i installed my Howell last month and did not see a filter or embedded circuit board in the harness. I was under the impression that the filter was used to flatten out the multiple fires into one pulse. and i guess maybe clamp the voltage spike.

If you can describe what it looks like. I can find it and could post a picture.

FYI, the guys at Howell said they would send me a tach filter free of charge if I decided to upgrade.

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post #7 of (permalink) Old 01-17-2004, 01:10 PM
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Re: Anyone install an MSD on their Howell TBI??

</font><blockquote><font class="small">In reply to:</font><hr />
All Howell TBI systems have a tach signal filter.

[/ QUOTE ]1. Tom, I've never heard this.
2. In examining my system...
3. I sure don't see one,
4. Nor is it mentioned in my Documentation .[*]See Page 10, Item 2[*]See Page 13, Item 5
5. However, it's almost 8 years old...
6. Things change...
7. But Take a look at Page 14 of the manual I sent ya,
8. There's no Tach Filter in line with the coil wiring.
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post #8 of (permalink) Old 01-17-2004, 01:43 PM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Alright LEVE......

You haven't cut into your Howell harness have you?

I did. There is a tach filter in the harness near the ECM plugs that is between the white coil(-) and the green B5 ECM terminal. It is a small circuit board .5x1.5"s. It has an IC, resisitors and capacitors.

If you notice in the manual you sent:
Page 13:
5. AFTERMARKET IGNITION SYSTEMS: If you are running an aftermarket ignition system (MSD, Mallory, Jacobs, etc.), you might not have a coil signal that will trigger our <font color="red">built-in tach filter</font color>. If your engine will not start, and you have one of these systems, contact Howell Engine Developments at Ph 810-765-5100 for assistance.
Page 10:
2. ............Connect the labeled white wire to the ignition coil negative terminal to pick up a tach Signal. NOTE: Multiple spark discharge ignitions require a <font color="red">special Tach filter</font color> to function correctly..................

It is in there it is just so small that you wouldn't know it. If I would have know about it when I started this project I probably would have gone another way. Now that my harness is built and installed, I can't live without one. I tried something else today using a GM ignition module parallel to my duraspark module, and it didn't work.

Oh well..... This should clarify the tach filter issue for anyone that is interested, or thinking about creating a fuel only TBI system.

Later,
Tom
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post #9 of (permalink) Old 01-17-2004, 02:10 PM
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Re: Anyone install an MSD on their Howell TBI??

1. Geeeeeez Tom, you really know how to make a guy work...
2. There are some modules like you describe,
3. Under the dash...but,
4. Having never looked at them I've always assumed,
5. They're toroidal chokes, etc. and buss points.
6. Now you've got my curiosity up...
7. It'll give me something to do this week.
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post #10 of (permalink) Old 01-17-2004, 02:23 PM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

The tach filter is really small. Smaller than a match book. It is covered with heat shrink tubing and then hidden by the tape wrapped around the harness. It is probably in the first 6 inches of the harness wiring near the ECM. Before I started this project I looked all over my Howell harness for any special gadgets and completely missed it.

Later,
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