Cam Break-in Day is finally here

Well that went off without a boom… literally lol. We cranked it for a couple seconds and I got no strobe from the timing light at all so I started troubleshooting no spark.

I guess it could be the timing light but how do you really test those anyway. Besides on a known running car?

I took a few readings from under the hood with my mulitimeter and they are not matching what I’m reading in different threads here so I’m going to have to dig deeper. The service manual has some good details but I think I just need to do some more testing.

My setup is stock, normal coil, distributor and points.

Battery is at 12.5 volts
With key on, I get 12 volts from the pink coil connector off the harness. I do oddly have 2 more pink wires connected to each other and a funny looking resister on the connector but it’s not being used.

Also with key on, coil voltage is showing 8 volts with points closed and 12 volts with it open.

Primary coil readings show 3.2 ohms… this is a little high but not terrible. Secondary coil readings show 8,400 ohms which is in normal range.

The wiring harness is from the 72GS 350 and is not new, the coil, distributor cap, wires, plugs are all new… the distributor and points are used but appeared in good shape.

I’m going to climb under the car now and check out my starter wiring, one of the smaller wires that were interconnected (and had round fuse looking bulges) was damaged and I had to repair it…. I can’t remember what all I did. I think I just cut out a frayed part and resoldiered it… leaving it only slightly shorter, I believe the fuse is still there.

Anything sticking out to anybody? I don’t think I’m supposed to have 12 volts to the coil but I’m not sure yet what’s causing that.

Thank you

 

To test coil. If you take the neg points wire off the coil and connect a jumper wire you can test spark by grounding on and off. You would be able to see spark jumping out of top of coil to coil/distributor wire.

 

Should be 12v in ignition start position only but 12v wouldn't stop ignition firing.

 

When I move the points to take measurements for open and closed it does spark there. And now with grounding it like you suggested it also sparks.

I thought I read that it should be less than 12volts , more like 8 when in the on position. And it only goes to 12 volts while starting. I get 12 right now just in the on position and not hooked to the coil.

thanks

 

Does the distributor turn when the engine cranks? Don't have a failed roll-pin on the gear?

Testing on another, running vehicle is super easy. Try it.

Charge the battery. A fully-charged battery should have 12.6--12.7 volts. Your battery is 1/4 discharged.

Pretty normal, although with the points closed, I might expect the voltage to be even lower. If the points are open, there's no current flow. Therefore, there's no voltage reduction through the ballast resistor wire. When the points close, current flows through the coil, and the ballast resistor drops the voltage. WHAT IS THE POINTS RESISTANCE? High points resistance would lead to higher-than-normal voltage at the coil, when the points are closed.

Do you have power to the ignition coil WHILE CRANKING? There should be a wire connected to the starter solenoid "R" terminal, that delivers system voltage (NOT "12 volts") to the coil when the starter is engaged.

That can be damaging to the plastic of the coil case. Easy to burn a track through the plastic, that will then conduct spark intermittently (or all the time.)

Use a spark tester calibrated for Points-style ignitions (Not calibrated for HEI.)

No. You'd have system voltage, not "12v" at the coil. The heavy amperage draw of the starter will reduce battery voltage to 9--10--11 volts.

 

Thanks Larry, I’ve ran across that post a few times in my research and I do not get those readings,.. I double checked that my starter is wired properly and with points open I get a reading of 7.5 volts. The second part of that test requires me to crank the engine over, I’m not ready to do that yet again but will check coil voltage when I do. I can only assume that I ran the 350 with these voltages. Worst case I can hook up my old starter and see if it gives me the right reading, then that would mean this newer starter has an issue.

Schurkey, the distributor does move with the engine and it does not free spin.

I tested my timing light on my 2 cylinder house generator today and from what I can tell the pickup is real picky on where it wants to be. It does work but I will have to have it right up against the plug boot to get the best results… the further I move it down the wire the less accurate it is. So it is possible that it didn’t strobe during my initial crank test even if everything was working properly because of this.

I tried to check points resistance and it wasn’t consistent. I have a new set of points and the results when tested were the same. Since points is a wear and tear item and I have no idea how old the set is I have now, I plan to replace them before I crank test again.

I feel I have done enough testing to attempt to crank the engine over again, my son and I will do that in the next day or so.

thanks again

 

With points OPEN, you should have system voltage.

With points CLOSED, I could believe 7.5 volts.

 

Ok.. here's my simple list when I can't get the timing light to strobe during a pre-start timing check.

1. Make sure the timing light is hooked up, to the battery correctly, and the probe is around the number one plug wire.
Test again.. turn it over for 10 seconds, some lights will take a second to activate.
2. If still no light, then take the coil lead off of the distributor, and put it next to an engine ground.. crank to see of you have spark from the coil.
If yes, then insure the distributor rotor is installed and in good shape. If it is, test the light on another engine.
If no spark, then we move into the electrical diagnosis of the ignition system.
The first test there is a 12V test light.. ground the light, then touch the negative of the coil.. crank the engine.. the light should flash on and off. If it is, but you have no spark at the coil wire, then check the coil wire for continuity, if it is ok, replace the coil and re-test.

If you have a steady light, with no flash (not a flicker, but a hard flash) then you have a primary ignition system issue.. proceed with your diagnosis on the distrib.

At this point in time, with any of the conversion modules, odds are it's the module that is bad. With points, check to see if they are burned, and opening properly, and test the condenser. If there is any problem there, replace both points and condensor, set the gap on the points to .016 and re-test.

It sounds like your ignition system is working, but the light is not. You will see 6-8 V on the coil when the points are closed, 12V when they are open..

JW

 

Yep, it was the positioning of the pickup lead for the timing light, it was just being finicky. The suggestion to check timing before even putting gas in it was right-on, that allowed me to check several things before it fired up. So right now we just finished 10 min of the break-in.... it got pretty hot and even after adjusting the timing to be optimum as well as making sure it wasn't running too lean... it still got warm so we quickly brought it down to idle and shut it off... it's cooling now. I will definitely have to buy a new radiator, preferably something that looks stock.

Here is a cool pick from last night, we cranked it over for the first time and it burped out this fireball... I made adjustments to fix the issue causing that and since it was late we decided to hang it up for the night. Today we tried again it took off without much fuss so the carb and timing are in a good place. 10 more min and then the hood goes back on and I go for a ride!

EDIT: All done now... time to tune it. So glad to be past that tbh.

Thanks everybody for the help and suggestions.

 

That’s what I was going to add as well mark. Run her hard to seat the rings after cam break in

 

Great! You might find this of interest: https://www.v8buick.com/index.php?threads/coldcase-radiator.365534/

 

Ironic you posted that Bill, I ordered one of those from Summit this morning.

 

I've been very happy with the one I bought!

 

Well, the cam break-in went well... I shot a video of it but it's pretty long... still working on it. I do have a video of my first drive though and seating the piston rings. Check it out.



I may need some advice on what to do about the RPM's, it feels like they should go higher.

 

Please go into more detail about your comment that “ it feels like it should go higher”?
Out of gear will it buzz to 5500 without backfiring thru the carb or the exh?

 

Steve, my shift from 1st to second is around 3500 rpm and my 2nd to 3rd is around 4k..... and in WOT at 90mph it is only at 4k RPM. For some reason I figured I'd be closer to 5k at 90mph.


Mark, it's a TH 350 that was rebuilt stronger for the 455 (about 2 years ago). The stall is around 2k, just slightly better than factory. When you say hold it in first... you don't mean to brake torque it do you? It will just roast the tires... I doubt the RPM's will get very high.
I have a 3.08 posi in the rear.

 

Shifting at about 4,100 rpm on WOT runs does seem low. If manually shifting isn't an ideal long term solution, you could recalibrate the governor to move the shift points up.

https://www.summitracing.com/parts/tci-326500

 

No brake torque, what I mean is put the selector lever in 1, shift to 2 at around 5000/5500 RPM See if it will pull strong up to there.