Msd Advance Curve
 

I am going to be installing an MSD distributor on my modified 454. How would I go about selecting a centrifugal advance curve. MSD shows a few graphs of the various curves achieved with different spring combinations, but how do you determine what curve will perform best.

Also, how many degrees of total advance do you guys use or recomend.

454 CI
MSD box
Med rise dual plane manifold
8.8/1 compression
hyd roller cam:
duration @.50 IN-224 / EX-224
max lift IN-.566 / EX-.566
lobe sepperation 112 degrees
89 octane
5000-5200 rpm

Re: Msd Advance Curve
 

I am running 34 degrees total with locked timing.
That is on a NA 540. I ran 29 degrees total with locked on my former blower motor.
This might generate some discussion.

Re: Msd Advance Curve
 

I don't have my MSD graph handy but one thing to keep in mind is that reguardless of which curve you use you'll be at full advance at about 2800 rpm. Not much more than it will take to be on plane. I run the weakest springs for 32 total at about 2400 rpm.

Re: Msd Advance Curve
 

The beauty of the MSD is the fact that it's so adjustable you can custom tailor your advance curve for any application.

If you want the ideal initial setting at idle, just hook up a vacuum guage under the carb and advance the timing until it pulls the most vacuum. Note where your timing is now at.

From the specs you've posted I'd say your motor will run the best at 34* total. Pick the lightest springs so all your advance will be out by 2500.

Now you need to select an advance-limiting bushing. Just deduct the amount of initial timing from your total advance. This figure will be your ideal amount of advance for your motor.

Example, if your motor pulls the most vacuum at 18* and your total is set at 34* you need to pick a bushing that will allow 16* of advance.

Just my .02 :D

Kurt

Re: Msd Advance Curve
 

I agree with Biggus, You want to have an initial timing your motor will be happy idling at in gear(and start), and then have the total advance limited to your WOT total your motor is happy with. Most boat motors go from idle to 3000 just to get on plane, and usually don't drop below 2800 once on plane, so as long as all the advance is in by 2800 to 3000 your good to go.

Example
12 deg initial 34 total by 3000 RPM (22 deg advance)
or
16 deg initial 34 total by 3000 RPM (18 deg advance)

Re: Msd Advance Curve
 

RLW nothing wrong with running a dist locked out in a boat as long as you have a start retard. The RPM comes up so quick in a boat (especially ones with high HP) and usually never drops below 2800 so your advance is always in anyway. But sometimes makes the carb hard to adjust at an idle with that much initial.

Re: Msd Advance Curve
 

Thanks guys. I guess the next step is to put the motor together and fire it up!

Re: Msd Advance Curve
 

I always use one light spring and one the next weight up. With all the rust you get in an MSD distributor, I want to make sure I have enough spring to pull it back.

Re: Msd Advance Curve
 

I have the ability to have the start retard or not. I run the MSD Digital 6 Plus.
I have experimented in both "modes".
I presently run fully locked with a 9.2:1 comp ratio.
Carbs have always been Nickerson 1050's. I have never needed to make any adjustments on the carb but see your point and it makes sense.
Russ

Re: Msd Advance Curve
 

Ran blown 540 w/ single 1050 dom MSD 6/mallery setup all last summer - I only ever checked total advance, and didn't notice till summer was over that dist. was set for only 5-6 degrees cent. advance (might as well have been locked) - so my idle advance was at 27-28 deg. - Shocked the hell out of me, but it idled great at 750rpm and had no starting issues.

Re: Msd Advance Curve
 

Starting issues only come into play when the motor is between 160 and 180 deg. so if your motor never sees this much heat no prob.

As far as idling issues all you have to do is adjust the carb richer than normal and in a blown app. the carb is usually fat at idle anyway. NA motors would have more trouble with idling than blown apps.

What happens is your firing the cyl to soon in real time, that's why there is an advance curve.

Re: Msd Advance Curve
 

After 300 some distributor builds for marine application, I have come to rely on a fairly standard curve. 0 at 400 rpm ( cranking speed ), 10 at 750 rpm, 15 at 1500 rpm and max calculated advance based on initial timing at 2800 rpm. Total of initial and advance not to exceed 34 in most NA applications unless ya got some real good gas. These are degrees measured at the crank. Remember that degrees of advance at the distributor must be doubled to equal crank degrees of advance. IE, 10 in the distributor = 20 at the crank.

Re: Msd Advance Curve
 

Careful how you say that. To us laymen, thats confusing. I mostly hear "10 in the distributor" as refering to how much mechanical advance is in the distributor based on crankshaft degrees. In other words, 10 in the distributor, plus 18 initial, equals 28 total. Never heard of it actually being measured "at the distributor" which is what your implying - is that just me??:D