Had a few minutes today to quickly check this. Per the linked article, the average solenoid reads 25ohms. Mined came in at 24.4. Does this mean the solenoid works correctly? If so, could it mean the manual adjustment (lean mixture screw) could still be off?
Quadrajet: Engine Knock, Bad Idle Mixture Solenoid...?!
- Thread starter G_RIDE_81
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Nope. Doesn't mean anything except your coil windings aren't shorted. If it was less than 10 ohms, that would mean the coil would be grouding out to the housing- no bueno. If it's badly worn, the plunger could stick and cause problems for the pri. metering rods. So if the adjusting screw is off, your solenoid could work great, but not be adjusted to meter fuel properly in the full lean position. The rich stop dictates the height of the plunger on its way up, to allow the metering rods to go to their fullest open position (full rich). Which is 1/8" total travel between the stops. The tool (1.304" spacer) sets your lean stop distance, and the rich stop is set afterwards to get your 1/8" total plunger travel, or "window".
You best know what you're doing when it comes to making adjustments if you start tweaking on stuff. You have a Chevy, and I haven't bothered to look it up, but you may have a 4 way adjustment system on your carb. Meaning adjusting your IABV and idle metering screws as well.
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So, finally got some time to wrench on the car. Since the last post, I came across articles regarding spark plug selection regarding reach, heat range, material, etc. So I decided to check what I had (ACDelco R44LTS6). The shop that swapped my motor installed these. Looked up what the parts warehouse where i ordered the engine from recommended, same plug specifications but with a shorter reach (Accel 576S).
For the life of me, could not find a heat range chart (hot to cold) for the ACDelco. The Accel breakdown is available. Anyways, decided to buy a set of the shorter reach Accel's. I have to say, the knock has damn near been illuminated!! If I drive at a lazy-Sunday-afternoon-cruise-speed, the knock is nonexistent from inside the car. If I drive normal (i.e. spirited), I can hear a faint sound. However, it is a barely perceivable sound and it occurs less often than before. When I ran the AC before, the knock would increase compared with not running the AC. With the Accel's and AC, again subtle knock, almost no change from running without AC on. Not completely solved but much better than before.
Does this change in parts and performance make sense? Anyone encounter similar situation? Any suggestions on additional tweaks I can perform to fully illuminate the knock?
Note: I do have a stock rebuilt CCC distributor purchased few months back I have yet to install. Could this help? The car starts and runs well for having what I believe is the original distributor.
Thanks again everyone for past and future comments!!
For the life of me, could not find a heat range chart (hot to cold) for the ACDelco. The Accel breakdown is available. Anyways, decided to buy a set of the shorter reach Accel's. I have to say, the knock has damn near been illuminated!! If I drive at a lazy-Sunday-afternoon-cruise-speed, the knock is nonexistent from inside the car. If I drive normal (i.e. spirited), I can hear a faint sound. However, it is a barely perceivable sound and it occurs less often than before. When I ran the AC before, the knock would increase compared with not running the AC. With the Accel's and AC, again subtle knock, almost no change from running without AC on. Not completely solved but much better than before.
Does this change in parts and performance make sense? Anyone encounter similar situation? Any suggestions on additional tweaks I can perform to fully illuminate the knock?
Note: I do have a stock rebuilt CCC distributor purchased few months back I have yet to install. Could this help? The car starts and runs well for having what I believe is the original distributor.
Thanks again everyone for past and future comments!!
AC Delco's numbers don't correspond to a given heat range in my experience. Whenever I want to get froggy with that I reach for NGK.
Your first character of R means resistor plug, the 4 means 14mm thread size, and the second 4 is your "heat range". ACDelco plugs go from 1-9, so a 4 is on the slightly colder side, but not overly so. In fact, that's right about on par with some of the performance Oldsmobiles in the early 70s, where R44 was the recommended plug.
Nice, thanks!
What I originally looked for was something like this with ACDelco on the chart. As you can see, the heat ranges do not line up perfectly. No luck though.
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I now feel the need to clarify: the newer plugs that I look at (usually a single or double plat) are usually a 2 digit number, and I remember trying to cross reference to find a colder plug to no avail. Unless you know something I don't 69?
As I understand it, the newer number Delco plug goes up to #10 as the hottest plug. NGK usually is opposite of that I believe. I don’t buy many NGK plugs. So cross-referencing between brands isn’t something I have any reliable experience to draw from. I’ve got enough old green ring AC plugs to last me and someone else the rest of our lives. In the correct heat range. 
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