Author Topic: Ignition Control Module suggestions  (Read 922 times)

Offline VileZambonie

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Re: Ignition Control Module suggestions
« Reply #15 on: February 13, 2022, 07:58:00 AM »
Well, your post here has been confusing. You started out this post by saying you have a racing coil and are dabbling in performance parts for what sounds like a stock truck. You are saying you use the truck to putt around, meaning there is little to be gained from an MSD system. If that is all you are using the truck for then back to what I originally said, stock, readily available is what you want.
,                           ___ 
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              ⌠ŻŻŻŻŻ'   [☼===☼]
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline TexasRed

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Re: Ignition Control Module suggestions
« Reply #16 on: February 13, 2022, 09:08:21 AM »
I think there's been a little misunderstanding. . . . you mean you priced out the components of cap, rotor, coil, coil cover, and module you figured it was cheaper just to buy a whole complete distributor? I don't think you need to replace all of it. I don't think it's the failure of the pickup coil either, but maybe . . . .

there's a ton of info here: http://garage.grumpysperformance.com/index.php?threads/trouble-shooting-rebuilding-hei-ignitions.2798/

I'd start by checking the resistance of the pickup coil. The connector is to your right of the module as you are looking at it in the truck. Should be two wires going into the connector. When disconnected from the module, the module will have one smaller blade and a larger blade. Be careful pulling the connector because inside those wires like to move. Using an ohm meter check the resistance between the two wires. See if the reading stays when you wiggle the wires to make sure there is no break. Should be about 500 to 1500 ohms. There should be NO continuity between either wire and the distributor body. Make sure when reconnecting the module to the pickup coil connector that it makes a GOOD connection. I've been bitten by this a few times when I got no spark. Also verify that there's at least a little of the heat sink compound between the module and distributor. Not a lot, but some.

The cap and rotor can be checked visually for the most part. You're looking for any melted pieces or burned through marks. Along with making sure there's a ground strap as mentioned earlier, is to verify that you have the button in there correctly. From bottom to top, it's cap, button, rubber gasket and then coil. You can also check the resistance of the button at this time too. Should be 5k ohms or less. If the ground strap isn't there, there should be a new one in the package if you buy a new coil.

I think you can get by with a stock style coil and module. You could either hit the boneyard for a cap cover if you need one or get it from rock auto. I wouldn't necessarily get AC Delco, since they don't make anything anyway. Like I said, stock STYLE.

MSD makes some decent distributors that are for use with a box only but I believe you can also wire in a 4 pin HEI module to run them as well as a potential back up. But I think that's pretty overkill for your application. A decent stock system with .045 gapped plugs and some timing mods should put you right where you want to be. I'd still say external coil, but that mod is a little more involved than you may want to commit to.

Profom makes decent distributors, they make the GM ones I think for some of the crate motors.

Offline fiddler

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Re: Ignition Control Module suggestions
« Reply #17 on: February 13, 2022, 10:13:29 AM »
Thank you.  When I got the truck it ran so badly that I wanted a good reliable strong spark so I did not have ignition issues to deal with so upgraded the ignition when I replaced it.  That said I don't think I have 15000 miles on this ignition setup.  Turns out the carburetor was toast and I had a myriad of vacuum leaks.  It was frustrating because as I found a vacuum leak there was another one going on so as I fixed one after another the truck didn't run better.  I plugged the brake booster line suspecting the sighing of the booster might indicate a vacuum leak and nothing got better so I dismissed that one  Took awhile to get back to it and then discover that I was running manual brakes and the thing was leaking vacuum all the time.  Anyway since all of that is fixed the truck runs like new and drives like new.  Also the truck has a edelbrock 1406 carburetor and edelbrock manifold so it kind of seemed like I should have the better ignition system...  I am going to do some more debug today.  Maybe give it one last run and drive it around the pasture for awhile before I put it out on the driveway...  I can work on it in the pasture if she dies on me again....Maybe get a backup distributor to carry with me LOL...
Ricky

Offline fiddler

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Re: Ignition Control Module suggestions
« Reply #18 on: February 15, 2022, 05:16:39 PM »
So to lessen the chance of being stranded out on the road and needing another tow I decided to replace that distributor.  It was actually at least as easy as replacing the ICM!  I got a MSD Streetfire from Amazon with my prime membership for 201 plus tax...no shipping charge.  It was in Mondays mail and I still don't have the parts I ordered to fix the old one.  I had a full plate yesterday so I did not get around to installation until today.  That has to be the easiest distributor installation I have ever done....  Anyway.. is it necessary to install the vacuum advance stop for a stock engine or is that a racing thing??  Or would you guys even use a vacuum advance on a racing engine? 

Ricky

Offline fiddler

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Re: Ignition Control Module suggestions
« Reply #19 on: February 16, 2022, 08:21:01 PM »
So the vacuum advance stop was necessary.  After an initial run up the driveway, (aggressive climb) indicated I was going to have pre ignition problems I installed the stop on position A.  No more ping.  It sounds different.  I think maybe there was a hint of a misfire happening on the old ignition setup.   Maybe that coil was breaking down and taking ICMs with it.  Anyway...Thanks for all of the suggestions.
Ricky

Offline TexasRed

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Re: Ignition Control Module suggestions
« Reply #20 on: February 18, 2022, 07:29:06 PM »
Do you have a timing light? Did the distributor come with extra springs to help tune? Is the vacuum advance adjustable with an allen key?

I think you'd be happier with a faster mechanical advance, less advance from the vacuum and adjusting the rate of the vacuum can.