Opinions on this engine miss and vacuum guage reading

Left to Right: 1357

 

1357 again…

 

Maybe.

I quit buying Champion spark plugs about forty years ago, because they had the most-brittle porcelains in the Industry. That, and soft, fast-wearing electrodes. In short, fookin' junk.

I haven't seen anything in the recent past to make me change my mind; although I have almost no recent first-hand experience with 'em. The only time I deal with Champion plugs is when someone else installed 'em, and I'm removing them in favor of another brand.

 

Yes. Numbers 6,7,8 all look a bit leaner compared to the others.

 

I just ordered some AC Delco 45s. Not sure where and when I got the Champions.

 

I double checked the carb air horn gasket and it’s definitely moist with fuel on the front and sides. Do I need to swap this? Double it up?

 

Are the air-horn screws appropriately tight?

How warped is it?

 

I have seen many more issues with “under-torqued” plugs than “over-torqued” plugs. Neither is good, but I’d put my money on under torqued causing a misfire than over torqued. Over is usually is a situation when it’s time for removal, and it doesn’t cause porcelain issues. Porcelain issues are caused from poor socket control. And Larry, IMO 1/16 of a turn past hand tight is not tight enough, but you do you. I like tighter than whatever the spec is. Looser causes random misfires, and if driven long enough, they’ll loosen enough to cause compression loss. Somehow they can still fire. It all depends. I have seen a lot. But you do you.

I’ve used countless Champion spark plugs w/o issue on everyday stuff, but I wouldn’t use them in our Buicks only because I like AC or NGK’s better. One of the worst spark plugs to use in anything are those “1.99” Bosch Platinum spark plugs. MANY issues with those, and it’s always from working behind someone else because I don’t/won’t use them. I spent almost a full day working behind someone at the shop I used to work at 30 years ago not once but twice trying to diagnose 2 different unusual driveability issues caused by those Bosch cheapie platinum plugs. Although I haven’t seen a vehicle with those in it in a while, SOP was to look for them first and absolutely require that they are replaced with the OE plugs or I close the hood and move on to the next vehicle. And this was back when I had GOOD “bedside manners”..

Regarding the Qjet possibly leaking. Typically if Qjet is flooding for whatever reason, the first thing you’ll notice is it runs like crap, esp at idle. Stalling, black smoke, etc. Pop the air cleaner, next you’ll see a lot of gas vapors and smell raw gas. Then you’ll notice a pooling of fuel in the accelerator pump stem cavity on the air horn (older Qjets didn’t have a stem seal like the newer ones). And finally a quick peak down the primary venturis confirms what you already know.

On this carb, perhaps the “reputable builder” would like to offer some advice. Without pictures, it’s difficult to say if it’s an issue. A damp airhorn gasket wouldn’t necessarily bother me too much. Like Jason stated, fuel sloshes around. Are the airhorn screws tight? Was a quality gasket used? Is something warped?

But back to the misfire, I would like some more info. Does it happen when you are just “revving” the engine in park or while you are actually driving? Heavy or light load if driving? Don’t get caught up with a vacuum gauge. They cause more confusion for the DIYers than a compression gauge does. I haven't used one in years. If I were you, I’d put your new AC plugs in and see what happens. No need to overthink this yet.

 

Idk if it’s warped but the screws weren’t super tight when I checked them. Maybe got a another half turn on them without cranking on them.
I checked torque on the carb to manifold and was at 13ftlb as specd.

 

The car idles very nicely but you can hear the occasional “putter” in the exhaust. When revving it in park is when the slight miss becomes more apparent. I know the miss is there when driving it, at part throttle I’d say is where it’s apparent.

 

New Plugs will arrive on Saturday. Will report back after install and test drive.

 

If you can isolate which cylinder is misfiring (disconnect one wire at a time and see if you can locate it), swap the plug wire with either a known good wire, or with one of the other wires and see if the miss follows the wire or stays with that cylinder.

Do the old "run the engine in the dark" when your eyes are accustomed to the low light. (take a 15 minute walk, then fire up the car in the dark and see if their is a light show. use a stick to move the wires around if there is slack. I have seen pinhole arc, and only be apparent when the wire was moved and then you see the spark.

Also look around the cap closely and the porcelain on the plugs.

 

Plugs look great

 

Larry, if the float level was a tad high, not high enough to cause fuel spillage but caused the airhorn gasket to be wet, then that would be the same as fuel slosh.

People understandably don't always know the proper vernacular on certain auto parts. On a Qjet, from top to bottom is the airhorn, float bowl and throttle plate. Any rendition is fine as long as it describes the part IMO. The OP mentioned the gasket between the airhorn and base of carb. Technically, there is no such thing, but I think we all know what he's talking about. The only time the gasket between the float bowl and throttle plate gets wet is when a full-fledged flooding situation is going on, as it doesn't seal any fuel. Radiators also have some misplaced vernacular - the # of rows is mistakenly called called "cores". There is only 1 core, 2 tanks, and a varying amount of rows. But we all know what everyone means, so who cares?

True story - I employed a tech once who was on the backside of his career. He had a handshake like shaking hands with a dead fish. He retired after a couple of years with us, but we started getting some unusual misfire "comebacks" after he left. These were on vehicles that "we" recently replaced the original sparks plugs with OEM replacements as routine maintenance. They should have gone many many years and many 10's of thousands of miles without a hiccup. One of the first things to do in this situation is to pull the offending cylinder's spark plug out, check for carbon tracking on the porcelain and check for oil or fuel contamination. Well, I started to see a pattern develop. It was always on vehicles that this gentleman previously worked on, and the spark plug was always not tight enough. A check of the other plugs showed an obvious pattern. So over 1000's of spark plugs that travel millions of miles from our shop, prudence dictates tighter is better than looser. Again, you do you as you see fit.

Another spark plug story. We sent our son to Alfred State College in Alfred, NY to go through their auto tech program. He already knew more than most of the instructors did on his first day of class, but we thought it would be a good experience for him in more ways than one (it was). He once texted me about when an intructor was "teaching" them about proper spark plug installation. The intructor told them to use antiseize on the plugs and torque them to half the "spec". I nearly lost my chit, but I bit my tongue as my BP went to the top floor. Fast forward to graduation day, and my son pointed out the instructor who was that was saying this, as we walked by. Again, trying to maintain the peace, I did my civic duty that day and kept quiet. But looking back, did I do the right thing? Now when I go to paid training classes, there is no filter! I look around and see young kids eager to learn, being spoon-fed bunk sometimes, and their minds are like sponges. It gets bad sometimes. But I can't sit by quietly anymore. And this just happened on Tuesday during an ADAS class. I gave the intructor several, polite opportunities to correct himself, which he didn't, so I called his boss the next day and was issued a written apology via email shortly thereafter. Now I don't claim to know everything, and there are certainly people who know plenty more, and like I've said I make plenty-o-mistakes, but daggone-it, some people might want to pay attention to what I have to say once in a while. I've broken a lot of trail. The hard way!