Ignition Timing

[Sandy]

Not sure why I didn't ask this before as it has been a question that I have been toying with for a while...

For more of a track car who runs a locked out ignition? I have been told by a couple of folks to stop screwing with the timing and lock it at at 34 degs for the 331 in the Mustang. I have a MSD 6Digital that retards spark 20 degs on start/cranking, so I don't think it would be an issue for cranking, but what about other issues. The MSD distro is set to full advance at about 2800 anyway and the car idles about 1600 as it is, and not doing too much until about 4k+ RPM..

Why/Why not lock it out and be done with it?

Sandy

 

[Jac Mac]

In the track day situation it 'should' be OK, BUT where it will catch you out is driving around the pits etc when you forget to keep it above 3000 at ALL times.

Jac Mac

 

[Gordon Levy]

I'll agree with Jac on this.
If you are concerned, put the black 18 degree advance bushing in the dist. with total timing coming in at 3000 revs. With total timing in the 34 degree range your initial will be around 16 degrees. This should give it really good responce off slower turns.

 

[Sandy]

Thanks Jac/Gordon!

I have the black timing limit slug in now, but always tricky to get the springs/idle all set up and stable with the quick (lighter) springs. The combination I used I think (will have to check) was light silver and light blue springs for the MSD Pro billet which was the quickest springs that would remain stable at idle. This discussion will force me look at all the parts and check them again and see what the timing is at idle and as the curve come up to full advance. What I should have done was play more with timing, and carb set up and I would have likely have a bit more stability. The engine does seem to like a lot of timing at idle and that will help the carb get back squarely into the idle circuits and off of the transfer slots which is a good thing, just have to do some work to get it all going.

This is good in any case, I'm guessing that I'll find something way off. Likely a good time to check the bronze gear too

Sandy

 

[Dean Lampe]

Sandy, Lock it out at 34 deg. It's just less to go wrong. I have ran a locked out dizzy for years and it works great. Most of the serious SCCA guys I know run this ways as well as the circle track guys. I think my cars have felt better with my timing locked.

 

[Randy V]

Likewise on the locked dist.. I would probably advise slightly less timing at 32 degrees. I've not seen much and usually no increase in power for the additional 2 degrees but have seen a pretty good increase in detonation in iron head engines. Aluminum head are more forgiving and will tolerate a little more timing.

I first tried a locked distributor back in the early 80's when Smokey Yunick told us to give it a try. Amazing in a small block Chevy as it is prone to spark scatter from oil pump pulsations. This really screwed with the mechanical advance weights. Locked it up and didn't look back. No more spark scatter - no more advance springs losing their tension after a half dozen races.. On those cars that experienced a starting issue, we put a momentary contract switch (Normally closed) right next to the starter button, just release the ignition interuptor button once the engine is cranking..
Jac's right also when it comes to low-speed driving.

 

[Rick]

Along with this be sure you don't short change yourself on fuel quality. I have seen a very high end SCCA Datsun 510 that had the ring lands cracked and broked from detonation and preignition caused by using substandard fuels and lower than normal rpms. This was with crank fired and locked ignition. Locked ignition and less than ideal fuel are a recipe for disaster.

 

[Sandy]

Thanks, all. I'm going to take a look at the 'system' and see if I can get it better before I try locking out the timing. I think if I can get a couple more degs in at idle and keep it under 34 that will help. Then will do a bit of tune on the primary bleeds of the carb as they are too big (as the builder of the carb said) for the amount of cam / centerline / low idle vacuum that I'm running. I only run 110 leaded in the car, and I don't think it would work real well on much else, fuel is not to much of a problem, just the operator and his ability to tune!

Locking out at 34 for cranking is not a problem for cranking either as the MSD pulls the ignition back 20 degs so if I do have to go that way, should not need to do much in that area.

Sandy