HEI making funny sound

[Burbinite]

Started up the Burb today and it started and idled w/ the electric choke on just fine. As it warmed up and the idle speed lowered, it didn't want to run if I put it in gear (auto). Then if I just let it idle it would die slowly (sputter) then start right back up. After this went on for a few minutes I noticed an eeeeeeeeeeeee sound coming from the HEI/Dist, almost like a balloon letting out air as you pull from each side gently. At first I thought it was a vacuum leak until it went away every time I keyed it off. If I key it on (ACC) only it starts making this sound immediately. Tach shows 3500-4000 rpms at idle w/ choke off (normally 600rpms). If any of you have got a clue I would greatly appreciate your ideas/help.

The HEI has a red cap and a black coil cover on top. It's an all in one unit with no brand markings that I can find (I have not taken it apart yet) I was tempted to take the coil cover off while it was whining at me but me and high voltage have met before and we don't get along real well.

[ChevLoRay]

Dang, neighbor....don't know about that noise but it don't sound good. I'm going to guess that the module has issues, but honestly don't understand how it could work like you say it does.

The sound...high-pitched? Could it be an electronic source? I'd be checking things that should be secure and tight. What I mean is the module should be placed into position after you use the proper amount of EJC (electrical joint compound), which insulates the module from the heat of the base onto which it mounts. I'd also pull the coil and see about the contact on the base of the coil, where it goes through the cap. I'd be looking for evidence of arcing, like burnt places where the contact is made.

Short of those things, I wouldn't know, but I'd sure be looking at those things. The fact that it runs says it is going to be something weird, but understandable when you find it.

[Hardway]

Did you take the cap off? Something inside the distributor or shaft is making some sort of metal/metal contact. I had a dist. in a 3rd gen Z28 make a similar sound, shortly afterward it stopped working. I never found out why, turned it in as a core for a rebuilt dist.

[willis0107]

sounds like your loosing your 12volts from your ignition

[Burbinite]

Thanks for all your suggestions. I didn't have time to dig into it today but I did key it on this afternoon to see if it would make that sound cold and it did. I never engaged the starter just ignition power only. To clarify the sound a little better maybe like a really sick headlight buzzer in a car.

I was just hoping someone would know what my problem might be. It will probably be Sun. afternoon before I can do a voltage check and start taking things apart. Any more suggestions before then are welcome!

[ChevLoRay]

I'd pull the cap first. I don't think that there's any issue with the module, after thinking about it. Since it makes the sound with just turning on the ignition, I'd be sure that the cap/coil contacts are up to snuff.

PM me and let me know where you are in Benton, if you want.

[mnunn454]

Sounds like a high voltage leak somewhere between the coil and a ground. I'd swap out the coil and cap, then look for internal arcing and maybe after that test the control module. Start though by verifying you have a full 12 volts + powering the distrib, even when the elect choke is on. Good luck.

[Burbinite]

Today I was able to do work on the Burb. I first confirmed 12+ volts and a good ground going to the distrib. Then I unplugged the control module (CM) from the coil and turned the key, no sound. (I never engaged the starter during all of this.) Then I realized the coil is grounded through the CM so I supplied ground via a jumper wire - no sound. It only makes this eeeeeeee/buzzing sound when plugged to the CM. I have continuity thru the coil. I then took the cap off leaving all wires connected to make sure where the sound was comming from. I was only able to get about 3.5-4 inches of separation between the cap and dist so I used the old tube in the ear trick - the sound is coming from the coil where the connections are. The cap and rotor do not look worn. According to the log book kept by the P.O. this setup has about 32K miles on it.

I am pretty sure this is a MSD-8501 http://store.summitracing.com/partde...1&autoview=sku. There is nothing on any of the parts to indicate MSD only going by looks. I really don't want to spend $170 to find out I replaced perfectly good parts.

This was installed by P.O. so I don't have data sheet/parts list or previous experience with this setup.

My main questions now are...

1. Am I chasing a white rabbit? Do you think this sound is what is causing my engine to die under load or at unchoked idle?

2. How do I confirm that the coil or CM is good/bad?

I thank you all who have responded w/ suggestions!!

[mnunn454]

Personally, I think its\'s sounding like a bad coil or cap. If you or a friend have a spare, just swap it momentarily to see if it goes away. Otherwise, replace the cap 1st (because it's cheaper) and if that doesn't eliminate it, then the coil.
My 2 cents