What's 30 degrees BTDC, suppose to set point gap when?

[H.G.P.]

Does 30 degrees BTDC mean I am suppose to set the point gap before turning the pulley all the way to TDC?

Or am I suppose to rotate the distributor or something?

Thanks

[Superman]

Not sure what you are asking, but point gap gets set first. Dwell angle will tell you whether you have set the gap properly. When that step is over, you turn the distributor to set timing. Lots of folks set timing at 25 degrees BTDC at full advance. In other words, about 5000 rpm. If the engine pings, back it off. Some do, some don't.

[H.G.P.]

Originally posted by Superman
Not sure what you are asking, but point gap gets set first. Dwell angle will tell you whether you have set the gap properly. When that step is over, you turn the distributor to set timing. Lots of folks set timing at 25 degrees BTDC at full advance. In other words, about 5000 rpm. If the engine pings, back it off. Some do, some don't.

Haven't started the engine yet (rebuild), so I can't have a dynamic timing. I think I have to do a static? Here's what it says:

The Haynes book p. 85 says "...Therefore, for those engines which require 5 degrees BTDC as an initial advance, the static timing point will be 5mm to the right of the TDC (Z1) mark..."

So my car will not start unless I set the points (or something) at 30 degrees BTDC?

[Eagledriver]

To set the points gap you must turn the crank or distibutor until the block(on the points) that rubs on the distibutor cam is at it's maximum lift. At that position you adjust the gap to specification. This is not setting the timing.

To set a static timing you should have the crank set to 5degrees BTDC on #1 (check valve positions to make sure you're not on #4). Make sure the distro is installed so as to have the rotor point to #1 spark plug lead. Now make small adjustments to rotation of distro such that the points just start to open up. When the points open the spark fires so this will be your timing point.

-Andy

[Bill Verburg]

To set the points gap you must turn the crank or distibutor until the block(on the points) that rubs on the distibutor cam is at it's maximum lift. At that position you adjust the gap to specification. This is not setting the timing.

Exactly, I'll just add that it's a lot easier to do out of the car in a bench vise. Not sure what year you have but the point gap for a Bosch dist. is ~.35mm(.014") after the distributor is back in the car a more precise measuremment of point gap called dwell angle can be obtained, again for a Bosch dist ~38&deg &#177 3&deg. if the dwell angle is too high open the point gap and vice versa.

[H.G.P.]

Originally posted by Bill Verburg
Exactly, I'll just add that it's a lot easier to do out of the car in a bench vise. Not sure what year you have but the point gap for a Bosch dist. is ~.35mm(.014") after the distributor is back in the car a more precise measuremment of point gap called dwell angle can be obtained, again for a Bosch dist ~38&deg &#177 3&deg. if the dwell angle is too high open the point gap and vice versa.

Ok. Here's what I understand and have done so far:

1. The car won't start if off timing by more than 20 degrees (I read from a Warren post)

2. According to Wayne's and Haynes, my 69 E is suppose to be at 30 degrees BTDC.

3. Point gap, Haynes Bosch dizzy CDS, .012 in, 0.3mm.

4. So today I set the gap, by rotating the crank to a high lobe.

5. Then saw by holding a small mirror down where the motor mount/ pulley location the marks on the pulley which are stamp on 30 and 32 degrees.

6. So I rotated the engine to approx. 30 on the pulley, with the point of the rotor "tip" (still not sure the exact "tip") tip pointed at the notch in the distributor.

7. At this point the points were still closed, so I loosened the dizzy and rotated slightly so the points just open at the 30 degree mark (slid a splice on paper down to confirm) (will try a light on/off method tomorrow.

8. I hope the distrib is in right as I don't think I can install it any better. And one other note, had to use an offset to get to that "down in there" dizzy screw.

[Bill Verburg]

1969E Bosch dist.
Static timing spec is 5&deg BTDC which is ~5mm to the right of TDC. Static timing is set w/ a 12v test light and manually rotating the engine.

Strobe timing spec is 30&deg BTDC @ 6000RPM

Set the static timing to get it started, check and adjust dwell to 38&deg &#177 3&deg to be sure, then and only then rev the unloaded engine to 6k w/ the timing light hooked up,

I premark my pulleys w/ a fleiurescent chalk so the timing marks show up better.

[H.G.P.]

Originally posted by Bill Verburg
1969E Bosch dist.
Static timing spec is 5&deg BTDC which is ~5mm to the right of TDC. Static timing is set w/ a 12v test light and manually rotating the engine.

Strobe timing spec is 30&deg BTDC @ 6000RPM

Set the static timing to get it started, check and adjust dwell to 38&deg &#177 3&deg to be sure, then and only then rev the unloaded engine to 6k w/ the timing light hooked up,

I premark my pulleys w/ a fleiurescent chalk so the timing marks show up better.

OK, I'll rotate 5mm tomorrow, but I really do not see the difference between the dwell and the gap. I see only one screw in there for adjusting?

[Bill Verburg]

Dwell measures the angle of distrubutor rotation during which the points are closed, bigger gap when max open means that the closed time will be less, smaller gap when max open means that the closed time will be greater. Its just a more accurate way to measure point gap. If you are good w/ feeler gauges it's not strictly necessary.

[H.G.P.]

Originally posted by Bill Verburg
Dwell measures the angle of distrubutor rotation during which the points are closed, bigger gap when max open means that the closed time will be less, smaller gap when max open means that the closed time will be greater. Its just a more accurate way to measure point gap. If you are good w/ feeler gauges it's not strictly necessary.

OK. Thank you.

[ruf-porsche]

Do people really set their timing at 6000 rpm? Aren't you afraid of putting a rod through the block?

[304065]

6000 RPM is what's called for by the factory manual. It's a little frightening leaning in with the engine howling like that. I make sure to remove my necktie when operating the strobe light.