suggestions on timing on 70 340, programmable ignition

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pld0vr

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Hello...

I'm running a programmable ignition in my 340 Dart. Carbs and weighted distributors are somewhat of a mystery to me, so I decided to handle ignition timing electronically, which I can tune accurately.

What I need is some baseline information...

I'm assuming an idle of 15deg would be ideal, with a slight ramp at the lowest rpm point to help with stumbles.

What I'm a little unsure of is when to have the timing all in by. Is anyone using an electronic ignition and if so what settings did you end up with?

I was going to start with 34deg all in... but at what rpm?
 
I'd start with it all in at 3000 and see how that works.

What are you using for a dizzy?

Steve
 
Well I have two setups to choose from. I have not actually installed it yet on this car, but as soon as I can figure out some base timing information I will do that.

I can either use the MSD Digital Programmable 6AL-2, which is actually kind of an annoying product really... bought it but might return it.. it only retards ignition with no way to advance it, which means locking out your distributor at high advance and retarding it where needed. The other issue is that the map sensor does not read vacuum, which means that you can't get any vacuum advance... which is nice to have for part throttle driving. What I could do is keep the vacuum advance in the distributor... i suppose that would work but I shouldn't have to in my opinion.

My other option... which I am leaning heavily towards.... I just upgraded to a newer version of megasquirt on my turbo car... so I have a megasquirt EFI system which I can rig up and use just for spark... it will to a 12x12 table based on map/rpm which does read vacuum and is much more configurable... retard at high temps.. etc... It will also have the advantage of expandability if I ever choose to go full efi.

The issue with the megasquirt is that I really need some serious timing information to fill that map... including what sort of retard would I need per psi on a 6-71... being that my motor has a fairly high compression at 10.5:1. I
m using a purple shaft cam if that makes a difference.

Either way... it's controllable. Stock dizzy I think.. will need to lock it out.
 
The 6AL-2 doesn't have different maps based on load? That sucks.

I think that 34 is going to be way too much with a blower. I'd start at 20 total and probably get it dialed on a dyno.
 
moper said:
What is the whole combo? bumper to bumber?
Click to expand...

340 .30 over
forged speed pro pistons
202 j heads
Forged pistons/rods 10.5:1
509 lift cam at 292 duration (PURPLE SHAFT)
flat tappet - hydraulic
6-71 around 10 or 15% overdriven
 
LXguy said:
The 6AL-2 doesn't have different maps based on load? That sucks.

I think that 34 is going to be way too much with a blower. I'd start at 20 total and probably get it dialed on a dyno.
Click to expand...

okay hold on here... I am not planning to run 34deg at boost. I can set 34deg for the advance at atmospheric pressure, and then retard the timing as the boost rises. I knew you guys were going to say that... that's why i didn't mention the blower originally.

It does do timing based on load, but only with boost (as a retard graph) and not vacuum... but yes, it does suck. Again... might just run megasquirt.
 
Alright... just to update I did install the msd system... and contrary to the manual and what it says in the tuning interface, it does read vacuum,,, but it displays the absolute pressure in positive psi which can be confusing... so what they sell as a 30psi sensor is reall -15 to +15 psi.


How much should I advance the timing at vacuum?
 
So how much boost is it capable of generating? The engine is really closer to 9.5:1 with those pistons and open chambers. So you should be ok. The cam is not what I'd use for a supercharged application. WAAAYYY too much overlap. That being said, I'd say sart with an initial timing figure of 10°, bring it up about 10°/thousand rpm beginning at 1000, with a max total of 32. Start from there and see what it likes.
 
moper said:
So how much boost is it capable of generating? The engine is really closer to 9.5:1 with those pistons and open chambers. So you should be ok. The cam is not what I'd use for a supercharged application. WAAAYYY too much overlap. That being said, I'd say sart with an initial timing figure of 10°, bring it up about 10°/thousand rpm beginning at 1000, with a max total of 32. Start from there and see what it likes.
Click to expand...

I would say 8psi. I like the overlap for the crap idle. This car is just a street toy... My fast car has a turbo... But its an import so you guys wouldn't like it.

Thank you for the suggestions.
 
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