[69 237]

I had the car running well last week. It idles stably (smooth 15inHg in drive at 650rpm), runs cool as mentioned in another post, and has plenty of power. It was grab when downshifting and keep chirping through second until I let off. I was content, but wanted to see how fuel and timing was by looking at the plugs. Turns out they're all over the place as you can see in the pictures (left pic is passenger side and plugs are arranged in order of how they would be in the motor). These are the NGK equivalents of R43 plugs. This was after idling for a bit when I got back in the garage.

4, 6, 1, and 8 are pig rich. 2, 3, and 5 look ok. 5 is a little wet, but ok. 8 looks too lean. The black ones are only black on one side of the valve. I wonder if it's partly due to poor fuel mix, especially with a 9:1 350 with large valve heads.

Any thoughts on what's up with this? Could it be inconsistencies with valve height, compression etc? The exhaust rather loud, but its consistent sounding and I don't hear valve train noises.

 

[PontiacJim]

Plugs may now be too cold with the better cooling temps of the engine. Go back to the factory R45 (hotter) plugs and you may see a difference. The equivalent R43 type plug is most likely too cold. Even Pontiac only went 1 step colder on the RAIV engine - R44. Most all used the R45.

This is the first thing I would try. Next might be a carb adjustment, but do one thing at a time and check results. :thumbsup:

PS, Idling could also be misleading for a number of reasons. Low air speed velocity with the bigger valve heads which is not atomizing the fuel at its best as fuel can puddle. The bigger cam, or even an over rich carb at your idle settings. The best way to check plugs is to do a full blast down the road and then shut the engine off while placing it in neutral and coast to a stop. Then pull the plugs and check the readings.

 

[69 237]

I'll try that, but with the NGK equivalent. NGK plugs color helps me to read them. I was tuning my idle before I pulled the car in. I made sure I had full control by richen the mixture until it bogged on each side. I also noticed the dark plugs are one cylinders that have the intake runners that run lower. Maybe it's a combination of low speed, over tightening when adjusting idle, and the low runners that were susceptible to the puddling.

 

[Lemans guy]

Reading plugs was much more accurate with the leaded gasoline of the 60’s, todays reformulated gas is not quite the same.

Check your PCV system it pulls oil and blowby from the crankcase and drops it right into the intake runners...depending how you He a it hooked up it can produce an oil wet plug on some cylinders and not others.

Also Like Jim said AFR can effect also. Plug temp for each engine is a bit different.....so you may have to try a couple..too hot you may get detonation and too cold plug fouling....

Timing plays a role as well

 

[69 237]

Good point. I'll try XR5 NGK plugs next. Similar plugs to what I have, but a step hotter. The only other difference is these are 5k ohm resistor plugs, not sure if that is a big deal or not. I'm currently using non resistor ngk plugs from butler.

Right now I have breathers on both valve covers. The passenger side is baffled and feeds into my open element air cleaner. I have a PCV valve and new grommet installed I'm the factory valley pan.

It seems odd to me they would look so different when the vacuum reading is so smooth. I would think if the AFR was so different between cylinders I would at least get the classic 1inhg sqay or a twitching needle.

Timing is 13deg at idle, 25 with vac advance. Around 33 total to be conservative until I'm more comfortable with it.

 

[Lemans guy]

Where does your PCV vacumn intake go in? From the PCV to intake, some intakes use two feeds some one. The PCV sucks the blowby...which is both inbreed fuel and burned fuel, the byproducts of combustion, some oil and all of those are hydrocarbons that gum up and effect AFR...

Your timing is OK, I would also try one bottle of Redline S1 in the gas tank...any parts store...it has PEA which is “Techron” and will clean any valve deposits and crud in carb fuel lines, it will clean a lot of that up. If it does not have “PEA” it is just snake oil....I think Redline is the best of the 3 or 4 products that have PEA.

Checking the AFR with a meter or emission analyzer may be the only other way, but I am with PJ as the plugs may have been just a tad cold and we are right now in the change from winter to summer blend gasoline.

Finally where the PCV drops in the intake runners can effect nearby cylinder mix more than others....