Missing at low rpm's. Diagnosis?

[714Speed]

Hi everybody. I've got a 71 350 4 speed. It's bone stock numbers matching with the exception of a new Edelbrock Quadrajet and a Mallory replacement distributor. Here lately, especially on hot days, the motor misses at low rpm's. It's not constant and it is not dramatic, just sporatically and some days it doesn't miss at all. I've owned it for 8 months and have not done a tune up yet. What do you most likely think is the problem? Carb (new), plugs, wires, points, timing issue? I'm not a master mechanic, but good at changing out parts and such.

 

[69MyWay]

Go ahead and perform a full tune up including setting the points...then start from there.

I would imagine this will solve the problem.

 

[714Speed]

69: When you say set the points do you mean install a new set of points or adjust the ones I have? Thanks. Neil

 

[CS72Roadster]

While you're in there, you may want to loose the points altogether and go with the Pertronix Ignitor II; still keeping your stock appearance. No more points, no more dwell. I was having a problem with the engine cutting out on the top end. I installed one about a month ago and like it. Problem solved.

CS

 

[TWINRAY]

If you drive the car alot, not just Sunday rides, I'd also get a breakerless ignition. I have points in both my vehicles and don't mind changing them frequently - along with the condensor. I don't know the lifespan of points but I would say if you get 10K miles out of them, you are pushing it. They get burnt pretty quick.

 

[cruzer99]

It is most likly missing all of the time, you just don't hear or feel it at higher RPM's.

 

[714Speed]

Yes, it does idle rather roughly now that I think about it. What is the cost of going breakerless?

 

[CS72Roadster]

Here's one for about 90 bucks on Ebay.

CS

 

[714Speed]

I can change out the wires and plugs in a flash, but the points I have no experience with as far as setting dwell and timing. To rule out wires and plugs as the skipping problem, would a bad set of points mess up a good set of wires and plugs? If not I will try this first. Thanks. NH

 

[Johan]

The first thing you should to is to buy a dwell meter and a timing lamp (you can find kits with theese along with maybe a vacuum meter and compression meter). This is very well invested money, and shouldn't be expensive either.

You set the timing by turning the distributor a little bit while checking the timing scale at the flywheel with a timing stroboscope lamp, and you set the dwell with a screw on the distributor (actually on the points) while checking on a dwell meter.
When you know it, checking and setting them both (if you have the tools) is actually much quicker and simpler than changing plugs.

 

[714Speed]

narrowing down a skip

I installed a new set of plugs and wires on my 350 today and now the car idles smoothly again, and it solved 95% of the "miss" or "skip" at low rpm's. I thought that I had completely solved the skip, but I finally got it to again, but then straightened out again. Do you think the problem will get better as I drive it? What would you ckeck next? Points? :gap

I'm definitely sticking to points, this Mallory unit is a "cadillac", at least according to its price.

 

[corvetjerryd]

I have mallory dual point in my 73 and I started having a missing problem with it that turned out to be a bad condensor.
But I went ahead and converted the distributer over to mallory uni-lite breakerless system and I've never had another miss.I got mine from Jegs....