Reading spark plugs ?

danny waters sr · 04-12-2011, 09:10 AM

I ran my 283 stocker this past weekend at MIR. ( L/SA )
Shut it down at top end after run and checked plugs ,they look like they just came out of the box.
I run the 4-gc carb .
My question is ,do i need to jet it up or maybe leave it alone since the weather is going to change to hot conditions very soon here.
The weather was very good this past weekend except for the humidity.
And if i change jets is it going to pick the car up very much if any ?
It seems to be sort of laying down at top end now (good fuel pressure at top end ) , but not popping or snapping ,just lazy feeling from just past the 1,000 ft mark to the 1/4. It ran a 12.18 @ 108 mph.

Thanks in advance for any info....

Bob Bender · 04-12-2011, 12:00 PM

I do not have anything trick but, I have a rich and lean carb I use. What you said it sounds lean. That 4GC is a pain to jet at the track so get another and faten it up a little.

Glenn1066 · 04-12-2011, 01:07 PM

What jets did you have in for that run? Dean Oliver is the guy to talk to about 4GC's, I have tried a multitude of different jet set ups and have found very little performance gain in the the 4GC. I have 67/69 jets in now and will likely end up with 68's in all. As for laying down at 1000 ft, it's a 283 all my car does on the top end is make noise!

Glenn

Bill Belden · 04-12-2011, 05:22 PM

I ran 64/66 jets when I ran the 283

danny waters sr · 04-12-2011, 05:27 PM

I have 65 and 67's..
It ran 108 mph and 7.64 @ 88 in the 1/8

cad · 04-12-2011, 10:04 PM

FWIW....We learned a lot on our local chassis dyno. We used the shop's O2 sensor in my O2 sensor bung. I do have headers extensions on my super comps. The key is...we took our Computech weather station with us and documented the CF, DA, etc. We jetted for 13.0 AFR. Now, we run the jet program on the Computech and it tells is whether we need to go up or down 1-2 jet sizes. We dyno'd at 2600' DA (dont remember the CF at the moment), and now we have our baseline. We know if we'll slow down or pick up based on the weather if we dont change jets. It took 2 hours and $150 which beats beating our head against the wall trying to repeat testing on the track for old school mph jetting.
IMO, reading the plugs is hit and miss. I only read them for the heat stripe (hot/cold) and base ring for jetting.

Clark

04-12-2011, 09:10 AM	#1
danny waters sr VIP Member Join Date: Apr 2007 Location: lagrange,nc Posts: 2,224 Likes: 1 Liked 0 Times in 0 Posts	Reading spark plugs ? I ran my 283 stocker this past weekend at MIR. ( L/SA ) Shut it down at top end after run and checked plugs ,they look like they just came out of the box. I run the 4-gc carb . My question is ,do i need to jet it up or maybe leave it alone since the weather is going to change to hot conditions very soon here. The weather was very good this past weekend except for the humidity. And if i change jets is it going to pick the car up very much if any ? It seems to be sort of laying down at top end now (good fuel pressure at top end ) , but not popping or snapping ,just lazy feeling from just past the 1,000 ft mark to the 1/4. It ran a 12.18 @ 108 mph. Thanks in advance for any info.... __________________ Danny Waters, Sr / 73 Duster "340"

04-12-2011, 12:00 PM	#2
Bob Bender VIP Member Join Date: Jan 2009 Location: Maryland Posts: 1,735 Likes: 1,601 Liked 460 Times in 91 Posts	Re: Reading spark plugs ? I do not have anything trick but, I have a rich and lean carb I use. What you said it sounds lean. That 4GC is a pain to jet at the track so get another and faten it up a little. __________________ Bob Bender 144 O/SA 2010-2012 National Record Holder

04-12-2011, 01:07 PM	#3
Glenn1066 Junior Member Join Date: Dec 2007 Posts: 69 Likes: 41 Liked 1 Time in 1 Post	Re: Reading spark plugs ? What jets did you have in for that run? Dean Oliver is the guy to talk to about 4GC's, I have tried a multitude of different jet set ups and have found very little performance gain in the the 4GC. I have 67/69 jets in now and will likely end up with 68's in all. As for laying down at 1000 ft, it's a 283 all my car does on the top end is make noise! Glenn

04-12-2011, 05:22 PM	#4
Bill Belden Member Join Date: Jun 2002 Location: York, PA Posts: 241 Likes: 0 Liked 1 Time in 1 Post	Re: Reading spark plugs ? I ran 64/66 jets when I ran the 283 __________________ Bill Belden Retired Stock Eliminator [emailSTK1100@comcast.net[/email]

04-12-2011, 05:27 PM	#5
danny waters sr VIP Member Join Date: Apr 2007 Location: lagrange,nc Posts: 2,224 Likes: 1 Liked 0 Times in 0 Posts	Re: Reading spark plugs ? I have 65 and 67's.. It ran 108 mph and 7.64 @ 88 in the 1/8 __________________ Danny Waters, Sr / 73 Duster "340"

04-12-2011, 10:04 PM	#6
cad Senior Member Join Date: Apr 2009 Location: Omaha, NE Posts: 703 Likes: 203 Liked 93 Times in 52 Posts	Re: Reading spark plugs ? FWIW....We learned a lot on our local chassis dyno. We used the shop's O2 sensor in my O2 sensor bung. I do have headers extensions on my super comps. The key is...we took our Computech weather station with us and documented the CF, DA, etc. We jetted for 13.0 AFR. Now, we run the jet program on the Computech and it tells is whether we need to go up or down 1-2 jet sizes. We dyno'd at 2600' DA (dont remember the CF at the moment), and now we have our baseline. We know if we'll slow down or pick up based on the weather if we dont change jets. It took 2 hours and $150 which beats beating our head against the wall trying to repeat testing on the track for old school mph jetting. IMO, reading the plugs is hit and miss. I only read them for the heat stripe (hot/cold) and base ring for jetting. Clark Last edited by cad; 04-12-2011 at 10:41 PM.