[George Zinger]

I just got done installing new 8.5 MSD plug wires with new plugs MSD cap and rotor in my 350 Chevy, a tame one. I had a previous post about some screws securing the rotor that had rusted. That all worked out ok and I am now back together and running. I have enough knowledge to be dangerous but now I’m not sure how to proceed. After having the MSD billet distributor out I wanted to be sure my timing was set correct, there are a lot of opinions about base timing and this is what I did. With vacuum blocked off I set timing to 4 degrees BTDC and it started and ran good. So I connected the vacuum then ran the rpm’s up to 3000 but my advance stopped around 18 or20. So then I tried another option set base idle to 10 degrees BTDC and it ran terrible. As I mentioned in the previous thread I was surprised how rusty everything inside the distributor was, I guess this is common with the HEI ignition (ionization?). As I said things were pretty rusty inside the distributor and I cleaned all the surface stuff I could get at. Springs on the top, one looked ok the other has some rust. The pickup was very rusty. Do you think this is where my advance problem stems from? In the written log the previous owner provided he did have the advance set for 32 degrees at 3000 rpm. I see that I can buy the internal parts and rebuild if you feel that is the answer? Suggestions and a current timing method are welcome. This is a daily driver do you see any issue with continuing to drive it? Thanks for any and all suggestions!
George

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[Rick_L]

Your distributor may be acting exactly as set up as far as mechanical timing advance. How much timing does it add right now?

 

[George Zinger]

With initial timing at 4 degrees BTDC it will advance to 18 degrees plus or minus. Is the amount of advance determined by the springs under the rotor?


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[Fun56Chevy]

try using ported vacuum.

 

[George Zinger]

Like I said, I know just enough to get in trouble….ported vacuum?


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[Robert Haas]

Like I said, I know just enough to get in trouble….ported vacuum?


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There is two ways to feed the vacuum advance one is direct manifold feed where you are plugged into a fitting directly off the manifold(Sometimes right out of a base plate below the carb) The other is from a ported outlet on the carb itself. What a ported outlet does is not open all the time. It has no vacuum at idle and opens when the butterflies begin to open and the pilot circuit comes to life.

You can set up an MSD to use both mechanical and vacuum to advance the ignition. You can also use their provided lugs to lock out total ignition. Some engines respond well to a lazy nearly retarded base line but get happy with a vacuum assisted advance to help with off idle low throttle low rpm operation. MSD distributors have a very tunable nature to them. Nobody is going to be able to tell you what springs, what bushings or even what total ignition your engine can run on an internet forum. Not knowing what cam, what compression, what carburetor, or even what cylinder heads you are running then I really can't offer any value to your tune.

That said. Rebuild or replace that distributor. If it is "Rusty" I can almost guarantee the advance mechanism is crap. Hell they are sticky when they are new. MSD sells every part of it and you will learn a butt load just by tearing it apart and replacing every wear part on it.

 

[Beach-n-cars]

Here is the manual for what looks to be your distributer. there is a lot of good reading here.

https://static.summitracing.com/global/images/instructions/msd-8360.pdf

im no guru, but just went through replacing my locked out distributor with a new one with mech and vac advance. i learned a ton doing this. What makes me curious is why you are only getting like 16-ish degrees of advance. Note that it appears the least advance is achieved with the black stop at 18 degrees. so, maybe your vacuum advance isnt working at all, or its locked out?
Just for fun, set your base timing back at 4 degrees, with the vac line disconnected and plugged. leave it disconnected and run the engine up and see what the timing does. if it runs back up to like 20 degrees, then you know your vacuum advance is not working. then maybe plug it back in and see if you get a different number.

I do think you may want to rebuild, or get a new distributor. i am pretty sure this is the one i put on, and it looks like we have the same MSD ignition box. it was fairly straight forward to install, change the springs, etc. changing out the stop bushing can be done with it in the car, but pay attention and take your time.

Summit Racing SUM-850055 Summit Racing™ Billet Distributors | Summit Racing

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The biggest issue i had is that my old snap on dial back light did not like giving me a clean reading on anything but idle timing. once i gave it some RPM and tied to dial back the timing, it would jump all over the place, like make you dizzy if you looked at it too long. it seems to be somewhat common with MSD boxes and some timing lights. I installed a timing tape on my balancer, and all works well, that way i dont have to use the dial back on the light.

 

[George Zinger]

Thanks for all the information and advice. As much as I hate to pull the distributor again I think I see an overhaul in my future. I’ve done enough looking to know for the price of the components I could probably buy a ready to go distributor from Summit but as I have just gone all MSD I think I will do the rebuild. I might call MSD/Holley tech line to see if they have a kit for this and if I can paint any of the components to prevent rusting. Besides I get some satisfaction from rebuilding rather than replacing. My time isn’t worth much these days! Again, thanks for all the help and some very interesting reading.
George


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[Wicked56]

Hi George. In 1999 I installed an MSD Pro-billet 8360 distributor when I built the 383 stroker for my 56 Chevy. Jump ahead to 2020. The car had been running poorly. I pulled the distributor cap and found this:

Apparently the humid weather in Florida rusted the distributor.

I decided to buy an MSD 85551 to replace the MSD 8360. The 85551 is about an inch shorter than the 8360. As you can see, the old distributor was pretty close to the wiper motor.

Here they are side by side....

The new distributor uses different wire ends, but it was time for new plug wires anyway. I also purchased MSD timing tapes for the harmonic balancer. The standard markings on the balancer do not go high enough to check/set total timing. Here is the sticker installed on my 8 inch balancer.

I see you are running an MSD ignition module in your photo. I am sure you know this, but if your ignition box is an MSD 6AL unit, the multiple sparks below 3000 rpm will require a special timing light. I bought this Perf Tool W80578 from Summit for $39. It is made by flaming river and runs off of 2 D cells. It is plenty bright inside my garage.

Now that you have all the photos, here is the important info. Both the MSD 8360 and 85551 distributor instructions state that depending on which "advance stop bushing" you use, the units will have mechanical advance up to 28 degrees with the Red (smallest) bushing. The default bushing installed from the factory is the Blue one, which limits the advance to 21 degrees mechanical.

The vacuum advance will "advance the timing up to 10 degrees during partial throttle driving (with 15 in/Hg of vacuum)." My distributor does not have a vacuum advance. It is locked out.

My settings:

The timing settings I chose resulted in a "Total Timing" of 36 Degrees BTDC at 1800 rpm. I used the light silver springs for fastest advance curve. I used the Blue "advance stop bushing" for a 21 degree limit, and set initial timing to 15 degrees. My engine runs 10:1 compression with a Comp Cams Extreme Energy cam:
Advertised duration: 284 intake/296 exhaust
Duration at .050 in. cam lift: 240 intake/246 exhaust
Gross valve lift: .507 in. intake/.510 in. exhaust
Lobe separation: 110 degrees
Hydraulic cam RPM range: 2,300 to 6,500
Rough idle

Total timing of 34-36 degrees works well for it. A tamer engine would not need that advance.

Just wanted to give you some details I used. I hope this helps when you rebuild or replace your distributor. Final photo .. you can see there is now more clearance for the plug wires under the wiper motor.

George, I hope this helps. Remember, this is a hobby, not a job.

 

[George Zinger]

Update and close thread as all set!! I’m old enough that when I see a win I take it! I’m not 100% sure what was going on, perhaps a tooth off but my timing was way advanced so wouldn’t increase with mechanical, not sure that is even possible. Between a 40 year old Sun timing light and my diminishing eye sight I was reading the Mr Gasket tape on the balancer wrong. I was thinking gonna pull the distributor but going back to basics I got the wife out and had her bump it to TDC or close and start fresh. Went step by step and now set at about 11 degrees BTDC and runs up to 32 degrees at about 3000 rpm! That’s the win I’ll take! Like I said not sure what I did, #1 plug I pulled was new but pretty black, hope it will burn off?
Future plan is to order parts for distributor to do a full refresh and new springs, save for a rainy spell when I’m antsy! Can’t decide on a new timing light as suggested at my age but I do like tools….. story has a happy ending and I appreciate the suggestions and education from all, I did learn quite a bit about timing by reading all the information given, thanks to all!
Happy Camper, George


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[Wicked56]

Update and close thread as all set!! I’m old enough that when I see a win I take it! I’m not 100% sure what was going on, perhaps a tooth off but my timing was way advanced so wouldn’t increase with mechanical, not sure that is even possible. Between a 40 year old Sun timing light and my diminishing eye sight I was reading the Mr Gasket tape on the balancer wrong. I was thinking gonna pull the distributor but going back to basics I got the wife out and had her bump it to TDC or close and start fresh. Went step by step and now set at about 11 degrees BTDC and runs up to 32 degrees at about 3000 rpm! That’s the win I’ll take! Like I said not sure what I did, #1 plug I pulled was new but pretty black, hope it will burn off?
Future plan is to order parts for distributor to do a full refresh and new springs, save for a rainy spell when I’m antsy! Can’t decide on a new timing light as suggested at my age but I do like tools….. story has a happy ending and I appreciate the suggestions and education from all, I did learn quite a bit about timing by reading all the information given, thanks to all!
Happy Camper, George


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Congratulations George!

 

[57 210 Wagon]

Wicked56, that's a lot of rust!!! So interesting how much it develops over time but not surprising when components are "out of sight and out of mind!" We hardly tend to pay attention until something runs amiss.