Best Timing Curve for a Mildly Built Big Block? MSD 6AL2 Programmable

[WaterBoy]

So I'm right in the middle of swapping the stock igniting in My 71 RR for a MSD 6AL2 Programmable unit. And I need to make the advance curve with the provided software because it doesn't come with a pre set curve. Picture attached is what I've come up with so far... I was thinking I'd set my total timing at 34 degrees and pull out 14 (so timeing will be at 20 degrees at idle) and start the bottom of the ramp at 800rpm and straight line it to 3600rpm where it will be at the total timing 34 degrees. Thoughts?
My engine is strong running 383, 10.5 compression, .477 .480 xtreme energy cam, ported 906 heads, 750 quick fuel with mechanical secondary's, dual plane mopar performance intake manifold, 1.75" long tubes and dual 3'' exhaust, 4 speed and 391 gears.

 

[Shorthorse]

This is not a scientific answer but I'll go ahead anyway. Back in the day we used to put in as much aggressive curve as it would handle. We would use the engine knock to determine that. Obviously, depending on the fuel octane we would simply back it off until the engine stopped knocking under hard acceleration.
On a more serious note. Have some fun. Since it's programmable, take it to the track on a test and tune night. Your results will be right there on the time ticket.

 

[Dennis H]

Would like to see a chassis-dyno report on your motor.

 

[Force Fed Mopar]

That's probably a good starting point. If you don't have any knock on that setting, I'd try bumping it up a little above 3600 until it either starts knocking or starts getting slower (depends on fuel). Once you get that bit right, then you can start playing with it below 3600 til you get best driveability.

Or vice versa, if you street drive more than race. That's what I would do anyway. Does it have any provision for vacuum (IE does it have a map sensor)?

 

[WaterBoy]

Thanks for the input guys! Finally got it up and running yesterday morning and its hard to believe the difference in drivablity at low speeds and idle! I'm happy with this timing curve so far but she doesn't seem to have the same pull above 4000 so I'll bump the total timing up to 36 and try that.

 

[WaterBoy]

That's probably a good starting point. If you don't have any knock on that setting, I'd try bumping it up a little above 3600 until it either starts knocking or starts getting slower (depends on fuel). Once you get that bit right, then you can start playing with it below 3600 til you get best driveability.

Or vice versa, if you street drive more than race. That's what I would do anyway. Does it have any provision for vacuum (IE does it have a map sensor)?

yes it does have a plug for a map sensor but I'm not running one because I didn't know a way to jimmy rig one to the old dual plane manifold. The MSD tech said it's not mandatory to run one. Do you think I should? If so do you have any suggestions on one that I couod rig to my manifold? thanks!

 

[747mopar]

I have a 400 stroker (456) that's comparable to yours, it like 30 at idle and 40 total. Pretty doggy off the line if it's set below 30.

 

[Force Fed Mopar]

yes it does have a plug for a map sensor but I'm not running one because I didn't know a way to jimmy rig one to the old dual plane manifold. The MSD tech said it's not mandatory to run one. Do you think I should? If so do you have any suggestions on one that I couod rig to my manifold? thanks!

I would run one if you street drive a lot, it helps at cruise and part throttle. Generally higher vacuum is leaner and therefore likes some extra timing. Map sensor doesn't have to be bolted into the intake, just needs vacuum to it. Most 80s-90s Chrysler cars had it mounted on the fender. Does MSD sell one that plugs and plays with the ignition module?

Also, if it runs good like it is up to 4k then feels flat, I'd almost say leave it at 34 to 3500 then start ramping it up to 36 at 4k, maybe 37 at 5k. It doesn't necessarily have to be a flat line...

 

[Force Fed Mopar]

FWIW I had a 318 once w/ an '80-something bottom end and '67 heads, Performer intake and 600cfm Edelbrock, and headers. Was running a late 70s vac advance distributor. Basically just a mishmash of parts I'd acquired cheaply. 3-spd manual. It liked 22-24 initial, no idea where the total ended up but pretty sure it was in the upper 30's, maybe even 40. Never ran hot, and it ran pretty hard for a truck ;)

So yeah, don't be afraid to crank the timing up there if it likes it.

 

[WaterBoy]

I would run one if you street drive a lot, it helps at cruise and part throttle. Generally higher vacuum is leaner and therefore likes some extra timing. Map sensor doesn't have to be bolted into the intake, just needs vacuum to it. Most 80s-90s Chrysler cars had it mounted on the fender. Does MSD sell one that plugs and plays with the ignition module?

Also, if it runs good like it is up to 4k then feels flat, I'd almost say leave it at 34 to 3500 then start ramping it up to 36 at 4k, maybe 37 at 5k. It doesn't necessarily have to be a flat line...

Thanks for the input Force Fed. I did what you suggested with the ramp and then bumped it up to 36 total and kept the initial at 20 and what a difference! I saved another 4 degrees of advance on the box so I have that much adjustment without having to move the distributor when I get it on a dyno for fine tuning!

 

[WaterBoy]

I would run one if you street drive a lot, it helps at cruise and part throttle. Generally higher vacuum is leaner and therefore likes some extra timing. Map sensor doesn't have to be bolted into the intake, just needs vacuum to it. Most 80s-90s Chrysler cars had it mounted on the fender. Does MSD sell one that plugs and plays with the ignition module?

I did some more reading on the map sensor and I found one that'll plug right into the box and I can plum to a manifold port on the rear of the manifold. I'm not completely sure but I think it's only use is for timing control in boosted applications. I'll have to give the MSD tech line a call on Monday to see if it'll help at all to have one I'm my application.

 

[Force Fed Mopar]

I did some more reading on the map sensor and I found one that'll plug right into the box and I can plum to a manifold port on the rear of the manifold. I'm not completely sure but I think it's only use is for timing control in boosted applications. I'll have to give the MSD tech line a call on Monday to see if it'll help at all to have one I'm my application.

It reads in vacuum too, and adds your specified timing according to the reading.

 

[furryfrog]

On my msd 6al-2 6530 I have my initial at 46, And I pull 24 degrees out at idle, have 36 degrees at zero boost and zero vacuum, timing starts dropping less than 36 into boost, and raises above 36 at vacuum. I have all my timing in at 2400 rpm, I think your should try ramping up your timing earlier. I am using an msd 2 bar map sensor. My engine likes having more timing under vacuum, I would recommend a map sensor and trying it, most defiantly with a street car.
I like this box, easy to use, engine likes it, strong spark. I checked my rotor phasing before retarding my timing that much with a locked rotor.

 

[WaterBoy]

On my msd 6al-2 6530 I have my initial at 46, And I pull 24 degrees out at idle, have 36 degrees at zero boost and zero vacuum, timing starts dropping less than 36 into boost, and raises above 36 at vacuum. I have all my timing in at 2400 rpm, I think your should try ramping up your timing earlier. I am using an msd 2 bar map sensor. My engine likes having more timing under vacuum, I would recommend a map sensor and trying it, most defiantly with a street car.
I like this box, easy to use, engine likes it, strong spark. I checked my rotor phasing before retarding my timing that much with a locked rotor.

Thanks for the info! Ok, I've got a bunch of questions for you but I'll just start with a couple haha.
-A 1 bar MAP sensor should be good for me where I'm not running any boost correct?
-Do I put less timing advance in it when the vacuum is high? Like say cruising on the highway at 3000rmp?

 

[Force Fed Mopar]

Higher vacuum = higher timing. Depending on combination you should probably be in the 40's for timing while cruising at 55 or so.

1-bar is fine for non-boosted applications.

 

[furryfrog]

A 1 bar sensor would be fine because your not running any boost, but I am not sure that the box your running is configured to work for a 1 bar sensor, I would check with msd. If i recall I had the option of a 2 bar or a 3 bar, and you need to select what sensor your using in the settings.

You would want more timing advance when the vacuum is high and when your cruising.

 

[Force Fed Mopar]

Yeah if you can't configure it for the map sensor you want to run, then you'll need the one that it's set up for. I only saw 2 and 3 bar options also when I was looking at them (me and a friend were researching it for use on our 4-cyl Chargers).

 

[WaterBoy]

Thanks very much for the info Force Fed! I'll call MSD to see which sensor I can use. When I get it all hooked up I'll shoot you a message with a couple more questions if you don't mind?

 

[Force Fed Mopar]

Thanks very much for the info Force Fed! I'll call MSD to see which sensor I can use. When I get it all hooked up I'll shoot you a message with a couple more questions if you don't mind?

Sure, no problem.