Spark plugs - Pontiac GTO Forum
User Tag List

 
LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 05-04-2019, 10:44 AM Thread Starter
 
Join Date: Feb 2018
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
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.
Attached Thumbnails
Click image for larger version

Name:	20190504_113255_1556984390037.jpg
Views:	38
Size:	731.5 KB
ID:	118693   Click image for larger version

Name:	20190504_113218_1556984409197.jpg
Views:	40
Size:	642.8 KB
ID:	118695  
69 237 is online now  
Sponsored Links
Advertisement
 
post #2 of 6 (permalink) Old 05-04-2019, 12:17 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,430
Mentioned: 0 Post(s)
Tagged: 1 Thread(s)
Quoted: 343 Post(s)
Garage
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.

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.

Last edited by PontiacJim; 05-04-2019 at 12:34 PM.
PontiacJim is offline  
post #3 of 6 (permalink) Old 05-04-2019, 01:44 PM Thread Starter
 
Join Date: Feb 2018
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
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.
69 237 is online now  
 
post #4 of 6 (permalink) Old 05-04-2019, 06:57 PM
 
Lemans guy's Avatar
 
Join Date: Oct 2014
Location: Nashville, Tennessee
Posts: 664
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
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
Lemans guy is offline  
post #5 of 6 (permalink) Old 05-05-2019, 10:03 AM Thread Starter
 
Join Date: Feb 2018
Posts: 48
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
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.

Last edited by 69 237; 05-05-2019 at 05:00 PM.
69 237 is online now  
post #6 of 6 (permalink) Old 05-06-2019, 07:59 AM
 
Lemans guy's Avatar
 
Join Date: Oct 2014
Location: Nashville, Tennessee
Posts: 664
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 52 Post(s)
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....
Lemans guy is offline  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
pulse plugs/pulsestar plugs htowngto04 Service, Maintenance and Technical Discussion 7 02-21-2009 03:14 AM
aftermarket spark plugs BlueBomber Service, Maintenance and Technical Discussion 13 01-06-2009 08:09 AM
What spark plugs for the ls2? Ozzhead Service, Maintenance and Technical Discussion 22 02-18-2008 12:23 PM
Will I benefit from different spark plugs? sdgoat Service, Maintenance and Technical Discussion 3 10-24-2005 09:13 PM
spark plugs? wannagofast 1964-1974 Tempest, Lemans & GTO General Discussion 2 09-27-2005 06:00 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome