425 engine techs please.

[Glen]

I was in Sears today and I saw those hand vacuum pumps there.    Be sure to get the ones made of metal.  The first version of those only came in plastic.  I went through at least three before I found Sears’ metal one.  It has lasted a long time. 

And they are very handy for a number of uses under the hood. 

Glen

[R Schroeder]

TIM - I rebuilt the carb. I did not touch the setting on the rods.  I think we are more inclined to lean to the distributor at this point.

Glen - Thanks.
Roy

[R Schroeder]

OK, here is where I am at.
Today I pulled the cap and checked all connections . I pulled the plugs that are inside dist, and cleaned all terminals.
I then checked timing per decal on the car. 22* at 1600 rpms. I got 23 *, so I left it . It is very hard to get at the bolt for the dist.
I plugged the vacuum line to the vacuum advance, plus EGR valve , before setting timing. I set the idle way down, as low as I could go, and checked how much mechanical advance I had. It moved up 12 *. As long as it was set up like this , I used the vacuum gage to set idle screws again. Right one was one turn off. Had to go in about a turn .
Once I had that all set up, I turned idle back up and connected the vacuum advance.
It showed the timing at about 22* , past the 24 * mark , on the timing mark.
I do have the later distibutor in the car. The AT one. Found the number right on the coil cover.
It now runs pretty good. No flat spot at all in 30 miles of stop and start driving with the exception of a idle at the stop light , if the light is  long. Then it was slight. But that was the only time it did it.

I was checking the coil out per manual. 77 manual. It says I should read O or close to it, across the TACH and DIST connections. It did.
I then checked from the center post , of the 3 prong post , to the center of the cap. That was good. O reading.
It also said to check from the TACH to the center post. It was suppose to read O, but I had no reading.
Don't know if something is wrong with the coil or not. you would think it wouldn't work at all if there was a problem.
So, thats where I'm at.
Roy

[TJ Hopland]

I have not usually had that sort if intermittent issues with coils.  For the most part they seem to work or not only intermittent thing with the oil filled ones was they would sometimes get funky when they got hot.

[R Schroeder]

This is the coil thats inside the distributor cap. I don't think they are filled with oil, like the external ones.
Just seemed funny that the readings didn't come out like the book said.
Otherwise, I dont know what changed , but it is working good now.
Roy

[TJ Hopland]

Those readings seem a little strange.      The 3 pin connector on the cap is just a link to the batt terminal on one side then into the + of the coil.  The other side is tach which again is a link and then to the - of the coil.  The middle pin is usually a ground bar to connect to the coil body.  Sometimes its a wire.    On the harness side middle wire just goes to the body of the distributor.  Batt wire is the B terminal of the module which is power for the electronics in the module.   The other wire is C terminal which goes to the tach terminal and the - of the coil.  This terminal is the equivalent of the wire that used to go to points.

[R Schroeder]

I'm going to have to look at the book a little more. Wasnt a very clear picture in the book.

[R Schroeder]

OK. I checked the book again and I do have the correct readings on my wires. Only the center of the 3 prong plug reads when you have the cap off. So, all leads were good, as well as the readings.
Roy

[R Schroeder]

OK. I'm going to bring this back again.
My final change that I made on the car , was to set the timing to 18 * at 1400 RPMs. Plate on car says 22* at 1800 rpm's , I believe. Repair manuals call for the 18 *.  This got rid of the flat spot. I drove through , Sept, Oct and all was good. I ran the car on one last trip , and it started in with the flat spot again.
  Well, I just went down back today and pulled the carb again. I wanted to go through it one more time and check all the settings.
As I went to take out the two front bolts, I saw they were loose. I have a lock washer on them , but I dont think it worked to well. I plan on buying the star type locks tomorrow. I also think I'll put something on the threads to keep them tight too.
So, I'm doing the carb over , just for kicks and then I'll check all the rest later.
I have read other posts about guys having flat spots ,so check those hold down bolts out , if you have a problem.
Roy Schroeder

[Bob Stahl]

I had a 1979 Cadillac Coupe and it had the hesitation right of idle. It ended up being the valve in the air cleaner snorkel. I had the tube on the air cleaner that went down to the cover over the exhaust manifold but the valve in the air cleaner snorkel did not work. I replaced the valve and the car never had the hesitation again. I was surprised that the valve worked all the time opening and closing even when driving. Even in warmer weather my car would have a small hesitation and that went away too. Hope I helped some?

[R Schroeder]

Thanks Bob,
I did replace all the valves in the air cleaner. That is all working correctly.
I rebuilt the carb again today. This time I went by the Cadillac repair manual for all the settings.
The float was low . 1/8 low.  I put it back on , and it seems to run much better. I didn't take it out, because the weather is getting bad . Had a tornado just south of me tonight.
Had it put away for the winter. Hope to get one more warm sunny day to check it out.
I'm pretty sure this might solve the problem.
Setting the timing to what the repair manual says helped a lot too.
Always open to ideas.
Thanks
Roy

[R Schroeder]

I couldnt wait until spring for the test ride in the car. I took the cover off today , and took her out.
Man , what a differnce. It really runs well now, with setting the carb to the Cadillac repair manual.
Now  I dont have to think about it .
Roy