I just installed a new msd pro billet distributor on my new motor. Its a mech advance unit but has the option to lock out the timing. I've never done this before and was wondering if this would be worth trying. i have a 350 with 144 blower, blower cam, and 750 mighty demon blower carb.

I'm not really sure how locking the dist would effect things. I'm going for a dyno tune on thursday morning and getting set up now.

right now I'm running 13deg intial timing and have an 18deg advance bushing installed for a total of 31deg total timing. I swapped the advance springs so all my timing is in by 2800rpm. If I locked the dist I would set the timing to 31deg at idle? How would that effect the perf of the car? would this increase the potential of detonation?

 

Basically, locking out the distributor just simplifies setting the timing, makes the timing advance more consistant, no chance of over advancing or retarding the timing at high rpms. Usually you will get a much better idle and more responsive throttle response because all of your timing is "IN" as soon as it starts. Also you may notice a reduction of running temps at idle. Really the only downside to locking it is if you run a lot of total timing, you could possibly have hot starting issues if you have a bunch of compression or marginal starting system.

Also, "locking" the distributor only locks the centrifugal section, you can still run vacuum advance if you want for more fuel economy BUT you will HAVE to limit the amount of vac advance you give it or it will detonate like mad....

I had been running mine at 31-32* locked and it ran perfect. Then in attempts to reduce hwy temps some and gain some fuel economy(which did not happen), I added the vac advance, but made a limiting plate to keep it at only 4.5*. With my initial set at 32*, then add 4.5* vac adv that gets me 36-37* at idle and light cruise, yet only 32* wot...that's worked pretty good so far.

Nothing wrong with a good working, curved dizzy but locking it just simplifies it, brings the timing in instantly and I don't worry about over or under advancing at redline.

 

[QUOTE=ajrothm;1575447867]Really the only downside to locking it is if you run a lot of total timing, you could possibly have hot starting issues if you have a bunch of compression or marginal starting system.
QUOTE]

My blower is from Magnum Supercharges. A local guy that's been around for at least a few decades. When I first got the blower, I asked about timing curves and he immediately suggested locking it out at 32 degrees. I asked about hard hot starting, knowing I had occassionally had issues at 16 degrees initial. He said all you do is hook your ignition up to a switch. So another words, you turn the ignition key, the motor starts spinning, and then you turn on your ignition. so that would be one method to combat hard starting.

I never locked out my distributer, but I did add the switch as a theft deterent.

I have considered trying it with the new motor. Heck it only seems to take micro seconds to be at full timing.

Good luck on the dyno. I'll be doing the same in the up coming weeks if nothing breaks before hand.

 

MSD makes a timing advance component. You install chips to set the onset of advance, arrival at maximum advance, and amount of advance. They may have a digital version of this now as well. Some units have a starting retard circuit so that starting is easier on the engine and starter. These are intended for use with locked distributors.

 

FWIW...I have ran mine locked out as high as 42* on 10-1 comp 496, Summit mini starter and and stock (but big) battery cables, never any starting problems, even dead hot in the summer.

I just keep it at 32* locked and no detonation issues and it's very responsive off idle.

Not a lot of power to be gained going to a locked dizzy but definitely takes out a lot of possible negatives.... I like it but my engine doesn't require much timing...

 

Locked out ignitions is a left over BUBBA idea from the days of Vertex magnitos used in circle track and sprint cars. Vertex mags were a very simple dual point without centrifugal advance. So some where along line Bubba said that if it was good enough for a race car it must be good for me.


Sprint cars are push started Locked out ignition is bad for starters, but even worse on rod bearings. You have little oil and no oil pressure when you first start a motor and you are slamming the bearings with max pressure from way over advanced ignition. I had never seen broken rods until I started working on Sprint car motors with locked out ignitions. We were some of the first teams to move away from those junky ignitions systems.

Now I have seen modern locked out ignitions working very well with one or two step manual retard switches or even boost activated retards

 

Locked out mags are principally used only for racing engines....Oil to the bearings is not really a problum if the engine is spun until you have a guage reading before turning the mag switch on.....

 

The reason I'm considering trying this is because I had the total timing set at 28deg (all in by 3300rpm) before and the car was sluggish when cruising and at light throttle. I have the biggest bushing in to limit advance to 18deg so I had initial at 10deg. The exhaust temp was up and the coating dulled on my headers after a short test drive. I advanced the timing to 31deg (all in by 2800rpm) and I have 13 deg initial and the car ran 10x better.

Another option would be to use the lighter springs in the advance kit and all my timing would be in by 1500rpm?

 

I run my MSD ProBillet HEI locked at 36 degrees and have not had any issues with it. My 406 is normally aspirated, but with a big solid cam and I was having idle issues before the locked timing. Vacuum was 7-8 inches, so the distributor vaccum advance was only causing me a lot of grief. I also had tried the black bushing limiter and had no success. Now it idles in gear at 1000, and shakes the fenders nicely.........

I have heard the downside of locked timing was a decrease in fuel economy,......I get 11 to 12 mpg's which is not all that bad for over 500 horsepower with no overdrive tranny.