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#1
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Spark Plugs and Timing?
Looking for a second opinion from the spark plug gurus in here. I "think" I know what's going on, but not sure.
What do you see here? These plugs are out of an aluminum IA-II, Speedmaster heads, 10.8:1 SCR, and street driven on 92 octane. Base timing is 18* btdc, total timing is set at 34*, but will get up to 38ish at cruise. The Edelbrock Pro-flo 4 dpfi doesn't like the 4.5" - 5" of vacuum at idle so I run idle AFR kinda fat. Note: There are only 2 different plugs in these photos. One of the plugs has a bit of water on it and kinda looks like melted aluminum under zoom.
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No! Do not try! Do! Or do not. There is no try. - Yoda 1967 Firebird Restoration 2005 - 1/25/2017 |
#2
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Looks like a couple points too hot on the plug and a little too rich.
Compression might be too high to run 34° but not sure from just looking at the plugs.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon. |
#3
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How does your timing go up to 38 when cruising if your total is 34?
Do you have vacuum advance?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#4
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"How does your timing go up to 38 when cruising if your total is 34?"
The Pro-flo ecu is controlling timing and can add advance when the vacuum is high.
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No! Do not try! Do! Or do not. There is no try. - Yoda 1967 Firebird Restoration 2005 - 1/25/2017 |
#5
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Here's what I'm thinking...
1) It looks to me that the base timing mark is too close to the end of the strap. 2) I don't see a total advance mark on the strap anywhere, which leads to 3) It looks like the heat range, color change, is 7 or 8 threads down. My guess is that the plug (NGK BKR5S) is (way) too hot of a plug and I should back it down to a 7 or 8 heat range. I've run heat range 6 or 7 plugs on previous iron block/aluminum head 10.25:1 builds with good results. Since this is an aluminum block/aluminum head build, I was advised to run a hotter plug. (I'm beginning to think I got some bad advice.) Which heat range would you suggest? (NGK = 1 is hottest & 10 is Coldest)
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No! Do not try! Do! Or do not. There is no try. - Yoda 1967 Firebird Restoration 2005 - 1/25/2017 |
#6
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7's or 8's. The so called timing mark is also affected by plug heat range.
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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
#7
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The fat idle AFR is throwing the plug reading off. The plug looks way rich, which throws off reading the strap because the carbon starts to cover the heat mark on the strap. And you don't know how much of that carbon on the insulator is from idling and how much is the actual WOT mixture. That's why they say not to idle when trying to read plugs.
Put a new set in, give it 2-3 WOT rips and shut it down. Then pull 2 plugs on each side and see what they look like. If you think you've got salt and pepper on the insulators, you need to slow down the curve so it doesn't come all in before 3000 RPM. If you go 2-3 heat ranges colder, it's may start to foul plugs. It's going to be a balancing act to keep the plugs clean if your idle AFRs are in the 10s or 11s.
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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 Last edited by chiphead; 05-07-2024 at 07:58 AM. |
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