Should timing light be consistent?

[Crom Cruach]

You tube link

I have some questions about timing, but first things first : shouldn’t the timing light flash EVERY time cylinder one fires? So looking at my video (warm engine idle, vacuum removed & plugged, 350 SBC) does the patchy light show that cylinder one is missing a few beats?

[Rancid87]

Check the pickup(part that clamps to the plug wire) and the wire to make sure they aren't damaged. Often the clamp or the wire will get burned on the exhaust and give erratic strobes.

[1970mcss]

also check the lead on the plug wire, make sure it goes the correct direction

[Crom Cruach]

The lead is going in the right direction, but it’s possible it got burned I guess.

Ok I’m having trouble calculating advance numbers. Here is what my Haynes manual says for my completely stock 350 ‘72 (auto, points)…

So ignition timing is 8 degrees. This is at fully warm engine idle? Manual tells me 600rpm final curb idle speed.

centrifugal advance 18° @ 4200rpm, 11° @ 2400rpm, 2° @ 1335rpm, and 0° @ 865rpm.

vacuum advance 0° @ 8 in hg (inches of Mercury?), and 15° @ 15.5 in hg. 

how do I calculate total timing with this info? I’m reading online 34 to 36 degrees total for an SBC. That tallies if max vacuum is at 2400rpm (cruising speed) so I add 8+11+15 =34° @ 2400rpm. 

and if I rev past 4200rpm I should get 8+18+0 =26° because there is no vacuum above 4200 is that right?

I tested today with vacuum removed and plugged, I’m at 4° initial, maxxed out at 16° at high revs. My timing light doesn’t have rpm or advance so with vacuum attached to the distributor it’s maybe high 20’s. I have a hard to start engine, and 7.5 mpg. My premium fuel is 95 octane. 

Sorry for the long text,  can anyone confirm if I am understanding this right?

[MC1of80]

Does the timing light you have, have a dial on the back of it? If not, I would start at setting the initial timing at 10- 12 degrees. Have set all the small block cars I have had like this. If your light does have the dial, have someone rev the engine to 2500 rpm and with the dial turn it till you see the mark on the balancer read 0. Where ever the dial is, indicates the total advance. All timing should be set and checked with the vacuum advance disconnected and the line plugged. 

[Crom Cruach]

No my timing light is basic, but I have a decent one on order including dwell, rpm and advance. Ok I’ll try 10-12 initial. Would you agree 600rpm sounds right for idle speed when warm?

[MC1of80]

No. 600 rpm in neutral is no bueno. It will most likely want to stall when put into gear. 

Give it a shot though, ya never know. I usually set it to around 750 rpm, in gear. Usually happy there. See what your car likes. 

[Crom Cruach]

Thanks Tom. By the way when you say ‘in gear’, do you put her in drive with the handbrake on and adjust idle?

[MC1of80]

Yes Paul. Prefer someone behind the wheel with their foot on the brake but that will work. 

[Scott S.]

Just not your kids....

[Dtret]

47 minutes ago, Crom Cruach said:

Thanks Tom. By the way when you say ‘in gear’, do you put her in drive with the handbrake on and adjust idle?

If you do it by yourself work from the side of the car not the front. Just in case. 

[Crom Cruach]

41 minutes ago, Dtret said:

If you do it by yourself work from the side of the car not the front. Just in case. 

I’m 6 foot 2 and I don’t think I could reach the distributor nut from the front! Solid advice though, I’ll put one of the kids under the wheel to stop it moving. I have one in mind tonight I tell ya 👹

 

by the way, set idle first or timing first?

[Dtret]

15 minutes ago, Crom Cruach said:

I’m 6 foot 2 and I don’t think I could reach the distributor nut from the front! Solid advice though, I’ll put one of the kids under the wheel to stop it moving. I have one in mind tonight I tell ya 👹

 

by the way, set idle first or timing first?

That will work. Make them somewhat useful anyway. They’ll have a new found respect for horsepower. Lol. 

[MC1of80]

Set the timing first. 

[Crom Cruach]

I have idle set at 750 in drive, but how do I set fast idle? I can see the notches on the fast idle cam, but I can't figure out how to lock it on it to the second notch to set fast idle.

possible related question. when the car is warm its ticking over beautifully now, but on cold start its still spewing out black smoke and idling rough. Would that still sound like a carb issue - rebuild kit & new float worth a shot? newbie here.

finally, I have initial advance set at 11, sounds lovely, but at 2400 rpm, total is just 21 (with dist vacuum plugged, and carb to air cleaner vacuum port plugged). if I rev higher it probably goes to 25 or more but I couldn't keep the gun and revs steady and read the timing mark at the same time. should I forget initial and just aim for 35 total advance at 2500rpm? initial lands where it lands?

also finally! my dwell meter shows 45 when set for 8cyl, but it didn't; change from 45 when I moved the dwell adjuster. Innova 5568 timing light. I followed the manual and turned it clockwise until the idle nearly dropped, then turned it a half turn back. seems good. am I doing something wrong with the meter?

thanks

[MC1of80]

Black smoke on cold start is choke related. Open it up a little more. The fast idle is also related to the choke. The choke has to be set first then fast idle. 

You still have points ignition? The dwell for points should be 28-32 degrees. 

Set with all the timing in at 2500 rpm. 

[Crom Cruach]

How do I open the choke - lower the choke rod?

[Crom Cruach]

On 5/19/2022 at 8:32 PM, MC1of80 said:

Black smoke on cold start is choke related. Open it up a little more. The fast idle is also related to the choke. The choke has to be set first then fast idle. 

You still have points ignition? The dwell for points should be 28-32 degrees. 

Set with all the timing in at 2500 rpm. 

Hi, ok I got dwell at 30. I set total advance at 35 (at 2500 rpm) but then initial advance is at 22. When I set initial at 11 total was 21. I left total at 30 as a compromise, any advice?

I know I’m close. It ran well at 11 initial, but why is my total so low? Should I be changing springs on the points, or should I believe the Haynes manual that says you should only get 11 Centrifugal advance at 2400 rpm?

will Pertronix plug & play just solve this?

[Crom Cruach]

Update: as the Haynes manual gave a figure for centrifugal advance at 4200 rpm (18°) I figured total advance has to be measured at that rpm. So with initial timing at 20° dwell at 30 and idle in drive at 750ish and timing at 2500 rpm was 30 advance.
 

So at 4200 rpm timing is now 37 advance! cold start is still lumpy for a minute, but no problem hot starting at 20° advance. Took her for a short drive and runs like a Swiss watch. 

the only issue is I can’t set fast idle above 1300 rpm - decal says 1500. Screw just keeps turning and was getting loose. Maybe that’s why I get lumpy cold idle? (See photo - correct screw?)

anyway, thanks everyone , I feel a large issue was solved with the timing setup and all down to your feedback. Legends.