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Discussion Starter #1
Hi all. With the engine rebuild I did over X-mas, I installed a MSD 8365 HEI distributor. When first installed it worked very well but recently I noticed it wasn't running as smooth. A local workshop put a timing light on it and showed the timing bouncing from 10-20deg at idle and shooting up over 50deg with an increase of revs. When it was first installed, it would sit rock solid on 10deg and under revs would be steady on 30deg total. I checked it at home again myself doing as MSD recommend (using a seperate 12v power source, plain jane timing light etc.) and had the same result. Surprisingly it starts great and runs great but I wont drive it, fearing detonation. Only a couple of months old, it is under warranty. Only problem is shipping costs as I purchased it from USA and I live in Australia. I've been told it may be a "module" and wondered could it be worthwhile replacing this first, to save shipping cost of around $150 anyway? I've taken the cap off and weights/springs all look OK.
Hope someone can help.
Cheers, Peter
 

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Check the weight return springs under the rotor to make sure one isn't broke. That will also cause you timing to be all over at idle.
 

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Loose timing chain?
Vacuum rock solid?
50° vacuum advance sounds normal for a HEI. Vacuum diaphram may need adjusting to limt the amount of vacuum advance. 3/32" allen wrench through the hose hole to adjust the total amount, I believe.
 

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Discussion Starter #5
Both springs are OK and the movement of the weights seems normal. The vacumm advance has been taken off completely. Apparently the distributor comes with a kit with different tension springs and bits to disconnect and remove the vacumm diaphram. The bloke that assembled my engine did this bit. He was a bit worried about it advancing too much since the compression ratio worked out to be 10.5:1 and not 10:1 which is what he aimed for. The only original parts of the 327 are the block (now +0.030") and the crankshaft. I used the rollmaster performance timing set which I presumed should be still OK. We also made a cam button for between the camshaft and timing cover so the camshaft shouldn't be walking. I've taken the distributor out and everything mechanical seems right. If it's electrical it's probably beyond me. A shame I tossed the stock dissy. I checked the voltage at the connecter that plugs into the distributor and it was 11.7v. Is there a minimum voltage this should be?
Thanks,
Peter
 

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If I'm not mistaken, electronic dizzy's need a full 12v to the dizzy, but I can't see that making the timing jump like that. It sounds like the ignition control module is going bad. What type of dizzy is it?
 

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Could be an oil pump problem, the pressure regulating valve. Common practice is to remove the valve, the item the spring fits into, and emery paper the circumference and reinstall.

A sticky relief valve will cause extra load and since dist is driven by camshaft, valve sticks and timing will be jittery. Obviously, a last resort effort since oil pan hasto come off. Another dist would be a good troubleshooting tool.
 

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Have you called MSD tech yet? These companies usually provide some knowledgeable support for their products. MSD Tech site: http://www.msdignition.com/1support.htm

Here's the tech line: 915-855-7123

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Here's the tips from MSD site:

Timing Fluctuations
If your timing seems to be jumping all over the place, check the following items:

* What kind of timing light are you using? Many lights have trouble reading the MSD's capacitive discharge multiple sparks. Dial back timing lights are not recommended. Try another non-adjustable light and check the timing again. MSD offers a Timing Light, PN 8990.
* Make sure you are not using Solid Core wires.
* Inspect the routing of the Magnetic Pickup Harness. It should be routed clear of the coil primary wires and plug wires. It is best to route it along a ground plain such as the firewall, frame or engine block to form a shield around it.
* Check the polarity of the magnetic pickup wires of the distributor. Reverse the connectors and check the timing again. The correct polarity is whichever connection gives the most retarded timing.
* On Chevrolet engines, if the timing is retarding 10 - 20 degrees inspect for cam-walk. This is especially prevalent on engines with a chrome or stock timing chain cover that is actually bowing forward allowing the cam to "walk".


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Discussion Starter #10
Thank you everyone for your help. Dave, I haven't called MSD Tech but I have emailed a couple of questions to them and I've also read numerous MSD forum posts. I have checked a lot of things they suggested with no luck. I agree that another distributor would be the best troubleshooting tool. 67CamaroRS/SS, you say the ignition control module. Forgive me for my lack of knowledge here but what does this actually do? Does it basically tell the distributor when to spark? Are they prone to breaking down or should they last for years? By the way, it is a MSD 8365 HEI distributor and I'm using MSD 8.5mm wires.
Thanks,
Peter
 

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Easiest test is to swap out the dizzy for a good one. Borrow one, if you don't have one. Then you'll know for sure................

-
 

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Discussion Starter #12
I agree. I will try and get hold of one and let you know how I go. Thanks to everyone for their help
Cheers,
Peter
 

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If the mechanical advance begins to kick in near the idle speed it'll run like crap. If you rev the motor to 2000 RPM or so and hold it there, is the timing steady?

HEI does advance pretty far as was said. I know a lot of people that have drilled holes in the baseplate and stuck a threaded stop there to limit the advance to 36 or 38* total. But that wouldn't affect running so much as getting you out of the detonation red zone.
 

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The module pulsates the fire. Without it or a device like it, the dizzy would not be able to stop firing that instant it takes to rotate from plug to plug. When the timing is bouncing all over the place, is the engine surging or is it steady? Another thing, have you checked for vacuum leaks?
 

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Discussion Starter #15
Well I managed to get hold of another HEI distributor and put it in on the weekend and timing was steady as. Just to double check I wasn't going crazy, I put my MSD back in and used the same timing light and again it was all over the place-if not worse. It was so bad it was hard to see what degrees it was on as it was bouncing from TDC to about 40deg @ idle. When I rev it a bit, it advances from there but is still bouncing. Yes 67CamaroRS/SS it is running even rougher now then when I first noticed it. It would be pretty safe to say though, that it must be the MSD, since when I put the spare in, it ran well and timing steady. I phoned Maddog Racing(where I purchased it from) and they maybe going to replace it. I just need to pay the freight from Oz to USA which is understandable. I very much appreciate all the input. May take a little while to get another one over here but I will let you know how I go. I'd be interested to know if anyone else has had a similar problem with their HEI distributor.
Thanks again,
Peter
 

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I don't know if anyone mentioned this or not, but beware that MSD ignition boxes will mis-trigger a lot of timing lights...especially the dial-back lights. But you said the engine ran poorly, so more than likely you found your issue.
 

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Discussion Starter #17
Hi Dave,

This type of distributor has the coil built-in and doesn't have a seperate box. I have tried three different timing lights and all had the same result. I'm almost positive there is a problem with the distributor. I have sent this off for a replacement and I will let you know how things go when I have installed the new one.

Thanks for your input,
Peter
 

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Remove the distributor cap and rotor. Try to rotate the "T" on the top of the distributor shaft. If the weld that holds it to the distributor shaft has broken it will cause this type of problem. I had a weld break about six years ago and it took quite a while to track it down.
 

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Discussion Starter #19
Just thought I would give an update on the distributor. I ended up getting a replacement MSD 8365. I wasn't even thinking it would have a problem but soon as it was installed, it did the same thing. I took it straight out and put another HEI distributor in ( different brand that I borrowed for a spare) and the timing is perfect and the engine runs sweet as. I contacted Anthony at ERW and he is doing the best he can to get it resolved. I've got to say this is a fantastic company. The after sale service couldn't be beaten. Maybe the third one might be a good one?? Appreciate everyones help.
Cheers, Peter
 

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Interesting............. MSD usually makes pretty good stuff. I never had a problem with any of their parts.

Thanks for posting.
 
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