Timing set up for my distributor

[K85 Octane]

I have an MSD HEI. I'm looking over the graphs and different ways to set up the timing with the provided springs/ stops.

The motor is a mild built 400sb w/'92 heads and 8.8 CR.
I'm not sure what the cam is, my uncle hasn't released that info yet lol, but he said it's a GM cam. I don't ask questions, I just fork over the money
So the truck is an all around driver, tow rig, Moab hopeful, rocks, fireroads, etc. It will be pushed to it's limit. I love all my vehicles, but not sure if they share similar feelings.

Which graph/ set up looks right for me?
I think the colors are Black=18. Blue=21. Silver=25. Red=28. Then you add initial advance for my total advanced. What would be a good start for initial timing @ idle?
Thanks

 

[4X4HIGH]

First off is this a dedicated wheeler that will not have to be smogged? The reason I ask is because if you have to smog it then the initial timing cannot be off by more than 4* otherwise it is an instant fail on an emission check. 1985 should be a computer controlled dizzy also and if yours is not once again it will fail the emissions test.

You will have to play with it and see what works best for your engine and vehicle but keep in mind that you want to stay between 32-36* TOTAL advance. Does the MSD you have use a vacuum advance? If so then you'll have to figure out how much advance that gives then add the initial advance then the rest will be mechanical advance and you might have to limit the amount to stay within the 36* total number.

 

[K85 Octane]

Hmmm. Let me change some details.
Lets say it's a 1985 K20 or K30 pickup. Those came with no computer, CCC, or CC Dizzy.
Lets suspend the idea it's a blazer for now, but yes it needs to be smogged.
It's an older OEM Q-jet w/ electric choke. The MSD is vacuum advance.
So I guess I need to check how many degrees the vacuum advance pulls?

Wow, so initial + vacuum advance max + weighted advance = 32-36*
If I'm out of this range, I will have stops 18-28* to work with. I wonder if vacuum advance is adjustable.

So lets say..
Initial = 4
Vacuum = 6 (I have no idea, just making it up)
Weighted stop= @25

Total advance = 35

Or I can go with a 21* stop for a total of 31* of advance. After smog I can bump timing to 7,8,9 and be within a total advance of 34,35,36.
Of course all this comes down to what the engine wants, especially during towing situations.

Even after finding out my totals, what kind of graph am I looking for? It's not a high rpm motor of course. I don't see playing around 4-5k at all.

And if it's not obvious already, I have no idea what I'm doing. I just know what I have.

 

[djtejas]

Don't figure the vacuum advance into your total advance if you are figuring 32*-36* of advance...most factory vacuum advance canisters give about 14* to maybe 20* of advance...with anything more than a stock motor, that's generally too much; I limited my vacuum advance to 10*, but I run my initial at 12*...even your MSD HEI might have as much as 14*, but it may be adjustable, some vacuum canisters are.

Vacuum advance only works during idle and part throttle...when you are under acceleration and WOT where your mechanical advance is maxed out, your vacuum advance will not be working; not enough manifold vacuum to work then.
If you figure vacuum advance into your total advance, and you adjust your mechanical to get 32*, you will not have enough advance under acceleration and WOT after your vacuum advance is not longer in affect.

I've found that with my vehicle, having all the advance in around 3,000 - 3,200rpm works pretty good for my Blazer. Check it with a timing light, don't just go by what the springs say they will be.

 

[79rustyk10]

I always use the lightest springs they have, so the advance comes in right away.

and again shoot for 34-35 total at 3500RPM or so. If you dont have one of the dial type timing lights, its definitly worth the money to get one. I have a craftsman that I paid $70 for I think. works great and is a huge tuning aid. A digital one would be really nice too, but they're more expensive.

 

[K85 Octane]

damn, no I only have "a handle with a light" timing light.