Setting Timing When Dist. Locked Out - Pontiac GTO Forum
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post #1 of 14 (permalink) Old 09-05-2015, 04:25 PM Thread Starter
 
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Setting Timing When Dist. Locked Out

Hi,

I have been reading up on setting my timing curve and tried it based on the posts found on this site. I have a MSD pro billet locked out and MSD 6AL – 2 programmable. It’s a 400 CI block bored .30 over. Note – This is all new territory for me, I have not done this before.

My goal was to be at 36* at WOT and when idling, 12*

1. Measure circumference of harmonic balancer = 16 and 7/8
2. Convert 7/8 to decimal and I get .875
3. Divide 16.875 by 10 and I get 1.6875 which converts to 1 and 11/16. This is the distance to 36* from TDC on the harmonic balancer (found this tip from a Lars post)
4. I marked 1 and 11/16 from TDC on harmonic balance and aligned it with 0 on the water pump jacket
5. Dropped dizzy in and pointed rotor at #1
6. Set software to retard timing by 24* from 0 – 1500 RPM and have it all in by 2500 which I believe will give me 12* of idle timing (see image)

Does this sound right? It starts SO hard now when both cold & hot, it doesn’t want to turn over easily and takes a few tries to start. New battery + high torque starter so I don’t think either of those is the issue. Is this a common problem when locking a distributor?
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post #2 of 14 (permalink) Old 09-05-2015, 04:47 PM
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Wow....that's a lot of work. It looks to me like you dropped the dizzy in place advanced about 25 degrees. You should always install the distributor at TDC with number one at TDC and the pointer at O. Then go from there adjusting the base timing by turning the dizzy and then on to mechanical and vacuum advance. Your dizzy is clocked wrong, and you are getting hard starting because it is way too far advanced. Great way to break a starter drive and ring gear teeth.
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post #3 of 14 (permalink) Old 09-05-2015, 06:35 PM Thread Starter
 
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Thanks geeteeohguy. The MSD tech support guy told me (unless I misunderstood) that that should I drop my dizzy in at the desired total advance, in this case 36*. Then, in the software, 0* is really 36* advance so retarding 24* gives me 12*. To be honest, I find most of this confusing.

I will take your advice and install dizzy at 0* TDC when pointing to #1, although if i do this, what will my timing be with a fully locked out pro billet dizzy? My head hurts.

BTW - I have no vacuum advance with pro billet.
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post #4 of 14 (permalink) Old 09-05-2015, 07:35 PM
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No vacuum advance on the street is not a good idea. Bad fuel economy, and high engine temps. Software has nothing to do with the mechanical relation of the crankshaft/camshaft and the the distributor being connected to the camshaft directly with a gear. If you drop the distributor in way advanced, like you did, the spark plugs will fire as the pistons are trying to come upwards on compression stroke: not good for the parts, not good for anything. The spark needs to fire near Top Dead Center on compression stroke....not 36 degrees before on initial timing. For over 35 years, I've enjoyed trouble free high performance ignition in all my GTO's using the stock distributors. The factory engineers had it pretty well figured out.
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post #5 of 14 (permalink) Old 09-06-2015, 02:08 AM
 
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Let me chime in here for a minute.
Since you have an HEI just turn the crank to 12 Degrees BTDC and then set the Reluctor points at each other. Car will start and be timed at 12 BTDC. with an advancing timing light, pull full advance RPM, probably 2600-2800 RPM and advance the light to match TDC to timing mark. This is your total advance. Slow engine down to idle and reset advance on the timing light to match TDC with timing mark. Look at readout on light. This is your intial setting. If you have a vacuum advance the setting could be as high as 23-24 degrees if it is plugged in below the throttle plate or at preset of 12 if the vacuum is plugged in above the throttle plate.
Hope this helps.

1964 400 4 speed Roller cammed RoadRacer
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post #6 of 14 (permalink) Old 09-07-2015, 06:32 PM Thread Starter
 
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I dropped dizzy in a 0* pointed at #1 and it turned over easily and started a little rough but runs pretty good. No pinging or knocking as best I could tell while going down the road. I have a dial back timing light and need to do a little more tweaking but I am in a better spot now, thanks for your help.
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post #7 of 14 (permalink) Old 09-07-2015, 07:37 PM
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Excellent! Now you just have to set your base timing (probably anywhere from 6 to 12 BTDC) and play with your advance curve. You're 90% there.
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post #8 of 14 (permalink) Old 09-08-2015, 09:13 AM
 
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A new balancer with timing marks is a tremendous investment for tuning, even a cheaper one at $125 for the street is fine. Itll help dampen much better over the stock stuff too.

Your graph looks like you have 24 degrees of timing on start up, then it shoots to zero degrees from 1500-2500 rpm and maintains zero degrees timing? Maybe im seeing that wrong?

Are you racing the car? If not my advice (which i dont mean to sound shitty) is sell off all that fancy mess and get a decent rebuilt or new HEI, throw some Mr Gasket gold springs in it to have all your timing in by 2800, 36 total and 14-16 initial. Accel sells an adjustable vacuum advance can for HEIs that is truely adjustable. I have mine only kicking in an additional 10 degrees for cruising cause thats what it liked most on 93 pump gas. Plugs look great, car runs great, with my 468 / 5 speed i get 16 mpg highway and awesome throttle response in the low end from the vaccuum can.

My brother had a locked out billet msd dizzy in his SB406 in a '71 nova that was in the 10s. Starter saver to get it running then it was 40 degrees locked cause it seen nothing but 3500rpm on the transbrake and 7000rpm all the way down the track. Great for racing but if you enjoy the street this is NOT the way to go.

An HEI and a 6AL box at most is all youll need for street car fun in my opinion. Lots of simple, cheap parts available for adjustments and tuning. On the other hand timing programming does sound kinda fun once you get it dialed in!

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Originally Posted by TonysGoat View Post

Does this sound right? It starts SO hard now when both cold & hot, it doesn’t want to turn over easily and takes a few tries to start. New battery + high torque starter so I don’t think either of those is the issue. Is this a common problem when locking a distributor?
Its starting hard cause you were rolling it over with 24 degrees timing is my guess.

You outta see her on a road course, or a quarter mile
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post #9 of 14 (permalink) Old 09-08-2015, 05:19 PM
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I had an MSD dissy when I first got the car, could not get it to run right to save my [email protected]@. Swapped it out with the original vacuum advance unit and fired the 6AL with the points. Never looked back. Plus I have the 6AL hidden so it looks totally stock.
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post #10 of 14 (permalink) Old 09-12-2015, 11:54 AM Thread Starter
 
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Hi guys - interesting feedback and advice.

I have been tinkering around with this and here is where I am at. I called MSD tech support and they INSISTED that when I have a locked out dizzy:

1. Set the crank to the desired max advance, in my case 36* (see my initial post above for how I found this point on the harmonic balancer)

2. When at desired advance, drop in dizzy and point to #1

3. In the MSD software, the higher the number you plot, the more the timing is retarded. I retard the timing to 24* 0-500 RPM, this means I am at 12* advanced while in that RPM range (36 total advance - 24 retard – attached is the latest curve)

4. It fired right up for me. I used a dial back timing light set to 36* and confirmed that once at 800 RPM (this is my idle) it is in at 36*

It has been running very strong and turns over OK and even starts while hot! I wonder if I was 180* out last time I tried this because it ran like such crap and didn't want to turn over?

Either way, thought I would share the latest developments.
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