Timing/Distributor Rotor Position-1970 LT-1

[Keith W.]

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[Leif A.]

Re: Timing/Distributor Rotor Position-1970 LT-1

When #1 cylinder is at TDC, #6 cylinder will be at TDC, also. One of them will be on the compression stroke and one of them will on the exhaust stroke. I bet your car has #6 at TDC compression stroke, hence, the rotor pointing towards the #6 terminal. Where is the timing mark on your balancer right now? My bet would be you can't see it. Bring the timing mark around to 8* BTC and then check the rotor position...it should, now, be pointing toward #1 terminal on your distributor.

[Keith W.]

Re: Timing/Distributor Rotor Position-1970 LT-1

Thanks Leif. The timing mark is at 0 degrees. This is what is confusing to me.

[Bill B.]

Re: Timing/Distributor Rotor Position-1970 LT-1

Rotate the crankshaft exactly one more complete revolution and the rotor should be pointing to the #1 position.

[Duke W.]

Re: Timing/Distributor Rotor Position-1970 LT-1

To verify TDC #1 remove #1 plug and have a helper cover the opening with a finger. Using a 3/4" socket on a breaker rotate the engine with the torsional damper center bolt, and as you approach TDC he should feel pressure. With the cap and rotor off as you approach a few degrees before TDC stop when the rotating and stationary pole pieces line up. Then see where the notch is on the timing tab. This will be the initial timing within a degree or two. This is called "static timing" the engine.

Remember that your '70 LT-1 spark advance map is set up for emissions, not performance or fuel economy. The best spark advance map would be that of the 365/375 HP 327s from the sixties with a 8" VAC signaled by full time manifold vacuum.

Details are in my tuning seminar that is posted in the "restoration documents" threads at the bottom of the "sticky section.


Duke

[Bill B.]

Re: Timing/Distributor Rotor Position-1970 LT-1

Duke,

I think Keith's #1 piston is indeed at TDC (or close), but on the Exhaust/Intake stroke peak, not the compression stroke peak, thus why his dist. rotor is pointing to #6, not #1.

[Keith W.]

[Duke W.]

Re: Timing/Distributor Rotor Position-1970 LT-1

Of course pressure will drop once past TDC because cylinder volume is now expanding. It only increases past TDC during the combustion process.

I don't have a photo, but the TI magnetic pulse distributor has stationary and rotating pole pieces. Each has eight sharp projections and the stationary pole piece is also wrapped with a coil of wire called the pickup coil.

You should be able to see the above with the rotor removed, and there may by a photo in the CSM or COM.

With the engine running as the rotating pole pieces approach the stationary pole pieces a voltage is developed in the pickup coil, which is transferred to the amp circuitry. As the rotating pole piece passes the stationary pole piece voltage drops rapidly, and this causes the amp to open the main power transistor shutting off current to the coil. This is the equivalent of the points opening on the single point distributor.

The above is why you can static time the engine by setting the notch on the torsion damper at your desired advance on the timing tab, and then rotate the distributor base until the points just barely open. This can be done either visually or with and ohmmeter. For the TI system the equivalent is when the pole pieces line up or when the rotating pole pieces are just barely past the stationary pole pieces.

Whenever removing the distributor or on a new build, set the crankshaft and rotate the distributor as above. This makes distributor installation easy and initial timing within a degree or two of where you want it. With a little practice you can get it spot on and leave the timing light in the drawer.

If the above description of how the TI works in incorrect, Richard Mozzetta will correct me.

Duke

[Richard M.]

Re: Timing/Distributor Rotor Position-1970 LT-1

Duke, You got it just fine.

For some photos of the TI Distributor items mentioned, see

This Thread, Post #7 has the photos.

Rich