Low RPM mis/no fire

[David Hawkins]

Hi guys.

My wife has decided at the last minute that she wants to take the car to Carlisle to park it in the corral...so I have to address its woes before she does this.

It's been missing for a while and I just got down to some diagnosis. Up to about 2000rpm, cylinders 3,6,5 are not getting any spark from the cap (I pulled the wires and held them close enough to see spark jump - the other 5 had spark...these three got nuthin'). Once the engine gets some speed, all 8 start to fire.

As you can guess, this leads to an extremely rough idle and terrible low speed driving characteristics.

I've replaced the plugs to try and fix this (which I now know it didn't need since the problems before the wire even) and it's got a new distributor that came with a new cap and rotor. Could it be a bad cap? Rotor? Points? Condenser? I'm used to modern FI cars, so I'm pretty much shooting in the dark.

Car's a 62, 300HP 327.

Any and all help/advice greatly appreciated.

 

[DINO1970]

Check the cap

At first I was going to suggest you replace the points and condensor, and then it occurred to me that the three cylinders you identified fire in sequence 184 365 72. Check the firing order at the cap and while your at it look for a misseated cap. Finally look for old wires that are cross firing. Changing the points and condensor just provides a reliable baseline . Don't forget to draw a clean business card between the points to remove any grease or oily residue, otherwise they'll burn as soon as you start 'em.

'DaGreek
57 Chevy Convert
64 Chevelle SS
Looking for a Vette.

 

[David Hawkins]

Thanks - I was thinking cap too, but figured I'd do some more troubleshooting before I start buying thing.

Turns out my point gap was about the thickness of a hair. I adjusted that to .020 and she's purring. I need to bring my timing light home tomorrow since I made my best guess on timing and it's backfiring on decel now - but this is the best it's run since we got it!

Makes me want to go Petronix more than ever now. My dad put one in our Corvair and that thing runs like a modern FI/HEI car.

 

[David Hawkins]

Hrm...doing a little more research, it appears I used the dwell screw to set the points. I'm assuming this is wrong? It worked...or at least seemed to...

If this car doesn't sell next week, it's going solid state.

 

[JohnZ]

Hrm...doing a little more research, it appears I used the dwell screw to set the points. I'm assuming this is wrong? It worked...or at least seemed to...

If this car doesn't sell next week, it's going solid state.

The dwell screw is how you adjust the points - do you have a dwell meter? Ignore the point gap - just adjust the screw until you see 30* on the dwell meter. Then re-check your timing (with a timing light) - the dwell setting affects the base timing, which is why you always set the dwell first, then set the timing.

 

[David Hawkins]

The dwell screw is how you adjust the points - do you have a dwell meter? Ignore the point gap - just adjust the screw until you see 30* on the dwell meter. Then re-check your timing (with a timing light) - the dwell setting affects the base timing, which is why you always set the dwell first, then set the timing.

Aha...got confused by some of the stuff I was finding that said to set the gap, then set the dwell with the engine running.

I do not have a dwell meter. I'm going to set the base timing tonight (had to come to the shop and get my gun) and see how it runs. Like I said, if we have the car after this weekend, it's getting a Petronix.