[aziz2010]

Hi,

I have a 70 Chevelle with mild 383 and would like to go to the strip. Engine has a pro-billet distributor (MSD) and sat at 15 degree initial with 36 total. A friend of mine told me to lock out the distributor and set the initial at 40 degree???

Car just for drag racing, so should I lock it out? And can I put that much of initial timing?

 

[Steve69SS396]

No. Cranking it up to 40 without knowing if that's what the engine needs is a good way to destroy it. If it runs best at 36 you could lock it there. Do you have an ignition box that has a start retard? If not, it could be difficult to start locked at 36. You say it's a mild 383. I would just put the soft advance springs in the distributor so you have full advance around 2,500 and don't lock it out.

 

[vortec710]

This "friend of yours" is doing you no favors with locked timing unless you are running top fuel, I will refer you to Dave Rays discussions on locked timing rather than taking the time to explain the disadvantages of this. First you stated a "mild" 383, second you did not mention trans or rear gear ratios which can help determine timing curves. Hydraulic lifter motor (?), max RPM's you plan to turn the motor, etc. 36 degrees can be hell on starter motors too.

 

[hydro462]

Make a mark on the damper at 30 degrees before dead center, use this as your new timing mark. Set it were you like. If you had a points distributor you caoul rem9ve the springs to the weights and have a retard start.

Mount a push button under the dash for the starter and a switch for the ignition. Push the button for the starter once the engine is spinning flip the ignition and it will rumble to life like never before.. Its really cool starting a engine like this.

This style ignition is just for race engines and not street engines..

 

[bracketchev1221]

Well, locking the timing can give you a benefit in a footbrake car. Since the timing is all there at idle it gives you a little more torque to help it leave. It also helps the engine idle better because you are using ignition advance to increase idle speed instead of the carburetor. The downside to locked out timing is trying to get the car started. If this is a low compression motor (under 11) you should be fine with a good starter and battery. Just winging the timing to 40 and locking it, well that's not the best advice. SOME engines can like that much timing. However, too much timing can hurt power. Ignition advance is the amount of time that you give the fuel to ignite, the flame to propagate and the cylinder pressure to increase to push the piston down. Optimally you want full pressure to occur that gives the most work into the piston moving down. If it is too early, the pressure is trying to force the piston down while its still moving up. Same thing if its too late, the piston is already on its way down too far, the pressure expansion is going to have less effect on the piston. My advice is, try it locked at 36, you may need an ignition cut off switch like was described above. Then bump the timing up 2 degrees and see if the car picks up MPH. If it does its making more power. If it doesn't then there is no point going higher. I found on my 548 that going from 36 up to 40 killed 4 hp. Not that big a difference, but why advance it for no reason.

 

[Georgia69]

I've had this argument so many times with so many people about locking the timing on my cars at the track. I don't use locked distributors on street driven cars, We have this argument because so many people don't know how a distributor works.

My distributor uses vacuum advance, and also uses a mechanical advance curve, with mechanical advance "all-in" around 2600RPM (adjusted with springs & advance stop bushing).

With a 2800 stall converter, engine RPM flashes to 2800 the instant I hit the throttle and the mechanical advance is therefore all-in instantly. Vacuum goes to ZERO the instant you go to wide open throttle, so therefore vacuum advance is NOT active.

Therefore, my timing is LOCKED at whatever total ADVANCE I set it for, from the instant I hit the throttle at the starting line all the way to the finish line when I lift. But I also still have both vacuum and mechanical advance curves for easy starting and part-throttle cruising efficiency.

As always, JMHO

 

[ChevelleFan70]

My distributor uses vacuum advance, and also uses a mechanical advance curve, with mechanical advance "all-in" around 2600RPM (adjusted with springs & advance stop bushing).

Here's the only thing I'll add to this excellent post -- experiment with whatever your all-in amount is -- someone mentioned above starting at 30. You can start low and work your way up and not cause damage. You don't start at 40, lol.. Set it to 30, make a pass. Come back to the pits and set it at 32, make another pass. Try 34, make another pass. Use MPH, not ET, as your guide. When MPH goes down, you know you found your limit.

-Dave

 

[mr 4 speed]

my street car looks 100% stock,runs high 11's on DOT tires with no headers,3.31 gear etc. and doesn't have locked out timing.