Tuning by spark plugs

Mr_Roboto

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A quick plug reading question, does AFR have any impact on the strap marks of a plug? Just wondering if I'm lean vs needing to pull timing. I haven't done a true cut (WOT pass, then stop) but the color overall seems good (tan) on the plug. Any thoughts?
 

JBruno88

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The proper way to read a plug is minimal idle time. If you're at the track, ideally you would want to push the car up to the line, do your burnout, make a WOT pass and shut it down right at the stripe and coast to shut off. Pull the plug there and read it for an accurate reading.
 
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Dr. Mom . Com makes a nice $25 otoscope that's great for reading plugs without cutting them open.

Looks of videos online that'll tell you what to look for and how to read them. As far as tuning goes for me, afr gauges can go in the trash. Only real way to tune, imo is by reading the plugs. Too cold or too hot, too rich or too lean, you'll get the idea of timing from them as well.
 

Great White Drake

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The strap will tell you if your timing is good or if the gap is too big or small. AFR is on the porcelain. The bottom tells you wot, middle of the porcelain is cruising, and top of porcelain idle.
 

Mr_Roboto

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The strap will tell you if your timing is good or if the gap is too big or small. AFR is on the porcelain. The bottom tells you wot, middle of the porcelain is cruising, and top of porcelain idle.
Cool, I'm trying to set timing in the MS box right now and the curve doesn't quite sanity check based on what I can figure out. It's a Pontiac 350 with a 214/224 cam, nearly stock exhaust, 4bbl intake/QJ and 8:1 compression. I may end up getting a compression tester and seeing what it says I'm wondering if it's got a bit higher DCR than I am giving it credit for.

Based on what I'm doing it doesn't even seem to want 30 degrees which seems extremely odd to me. I'd have thought it would want closer to 36. Maybe I'll toss the skinny rods back in the secondaries and see if it acts any better.
 

Great White Drake

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What kinda heads? The more efficient, the less timing you'll need. Also, is it hei or points? What springs in the distributor or do you have it locked out?
 

b00sted

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Did you verify the timing with a timing light? Do it at idle and ~4-5k rpm and make sure it's the same as what the box is commanding.
 

Mr_Roboto

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What kinda heads? The more efficient, the less timing you'll need. Also, is it hei or points? What springs in the distributor or do you have it locked out?
The heads are stone stock 71 Pontiac, and it is HEI. They are not true wedges but far from modern. Curve is actually a megasquirt in ignition only.

It is just odd to me that this is saying it wants the timing it does. From what I have read this should be near 36 all in. Maybe I need to pull the piston stop out real quick.
 

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