Topic: Reading Plugs - How do these look?
in Forum: C3 Engines
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Hey guys, how do these plugs look? They came out of my rebuilt engine with about 1.5K miles. I'm pleased that there is nothing too unusual to my untrained eye, and the fact that they're at least consistent seems to be a good thing. What do you think?
FYI, went back in with the real deal, AC Delcos, R43LTS - we'll see how they do. (That number may seem unusual to some of you but it's because I have Vortec heads - they require a different type of plug)
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Overall, they look fairly decent. Looks like you may be getting some crappy fuel, tho. Appears to be a lot of ash buildup on a couple of the side electrodes. The light tan color looks nice, but there are a couple that are noticeably whiter/leaner than the rest(#3 & 5). In fact ALL of the plugs on that side look whiter than the plugs on the other side. Not any major issue...just a little funny looking, imo. Does your car still have the heat riser valve on it, and if so, does it actually work? Might also point to a small vacuum leak that only effects one side....
Bottom line, they look fine to me, for a driver with so few miles on it so far.
Bottom line, they look fine to me, for a driver with so few miles on it so far.
Joel Adams
C3VR Lifetime Member #56 
My Link 
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Here's a link to a bigger/higher res image, if that helps.
|UPDATED|9/23/2013 8:03:12 PM (AZT)|/UPDATED|
Joel, I think the whiter color on the #3 and #5 is just the way they are rotated. All of the plugs have a mix of tan and white on on the insulators, but they look more white if they are turned correctly.
As for the fuel, I'm using pump premium, usually from Costco, sometimes from Shell. 91 or 92 octane. 10% ethanol or less, but I think in the summer around here it's lower. Suggestions on what to do to improve? Looking at them closely there is not much ash on the ground strap - they're pretty clean. So is the inner electrode. The ring around the tip where the ground strap is attached is a little sooty.
(inserted live link-aapple)
|UPDATED|9/23/2013 8:03:12 PM (AZT)|/UPDATED|
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Oh and I have wondered about the difference between the two banks, not necessarily due to the plugs, but the two sides of the exhaust sound a little bit different. I've been wondering if it might be just the idle screws aren't balanced correctly. I have not done much tuning on the carb in the last year since it's been running pretty darn good with my initial settings and I don't want to mess it up!
And no heat riser on a '76 L48, at least as far as I know. There is a spacer thing where it would go, but no butterfly valve inside it. Seems correct based on the AIM - I think L82's had the riser.
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Lifetime MemberModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Same pic, for me....
|UPDATED|9/23/2013 8:11:49 PM (AZT)|/UPDATED|
The plugs don't really look out of ordinary, really. I could tell more if I had them in hand, but overall, they look otay....the center electrodes are still nice and square(not rounded).
I would have to put the odd coloring that I am seeing down to fuel quality, or whatever additive packages they use in your part of the world. But the side electrodes look like they have some poo built up on them, in the pic. If you are looking at them, and don't see any, then it's just the pic that makes it appear that way to me.
A carb adjustment would effect all of the cylinders, normally...not just one side of the engine. However, if there is a vacuum leak, it can effect only one or two cylinders on one side of the engine, depending on where that leak may be. 
I say drive it!
what I really mean is...DRIVE IT!!! Get that puppy out and stomp on it for a few seconds....blow some of that soot out......
|UPDATED|9/23/2013 8:11:49 PM (AZT)|/UPDATED|
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Thanks again for your input, Joel. I'm liking your last bit of advice - can't wait to DRIVE that thing again! We've had a spate of bad weather here, but I'm thinking this weekend may be OK. And the new Delcos I put in are slightly colder, I believe, so a spirited drive now and then will definitely be in order.
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
in Forum: C3 Engines
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