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Discussion Starter #1
10:5-1 406 sbc with aluminum vortec style heads 93 octane. 32-34 degrees of locked timing.
At the track it ran 0.5mph faster in the 1/4 with 34 degrees compared to 32. Plugs have about 300 miles on them or so. They are a -6 NGK... last season I used a -5 NGK. Ran the same. How do I tell if the plugs are too hot or too cold?



 

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^^^^ X2
 

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I would honestly be running a -7 plug. Either way, you need to make a pass on a new set of plugs to get any useful data from them.
 

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Discussion Starter #6
I would honestly be running a -7 plug. Either way, you need to make a pass on a new set of plugs to get any useful data from them.
OK. I didn't think I would need to go that cold on a engine like this. Good point, I will try and grab a new set and find a place to "make a pass" lol
 

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Discussion Starter #9
36 to 38 degrees of timing is my vote
Are you stating that by looking at the plug? Most vortec heads are lower timing than old school sbc stuff.

7= hot, 9= cold, on NGK
I know. I ran a 5 last season and a 6 this season. I think a 5 is considered "stock". I didn't think this motor would need to go all the way to a 7, but if you think this plug looks too hot I will give a 7 a try.
 

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Discussion Starter #11
yep, I would keep going up 2-degrees until the et stopped gaining, not all vortecs like low timing,, then I would drop to a colder plug. 5's definitely too hot. I would grab a set of 7's like previously stated.
Does the timing marks on the plugs look low?
the car did gain some going from 32 to 34 degrees.

I will order a set of NGK 7s with non-projected tips
 

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Discussion Starter #12
would this be a good plug to try? It is a 3/4 reach, 14mm, gasketed plug. Also has a 5/8th hex which I think I might need to fit the hole in the head.

NGK R5671A-7/4091
 

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While there does appear to be too much run time on those plugs....

On the second plug you can see the timing mark just past center of the bend.... as you go upwards directly over the electrode on the ground strap you can see another line where the CAD is completely burned off the ground strap... infact the end of the ground strap looks pretty crispy..... That plug is too hot but timing is pretty close on that cyl.

Hard to read anything on the first plug. Looks like the CAD is still on the ground strap and I don't see a discernable timing mark... but that could just be color from fuel dye.
Will
 

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Does the timing marks on the plugs look low?
the car did gain some going from 32 to 34 degrees.

I will order a set of NGK 7s with non-projected tips
Can't really tell from the pics, but I never had any built 23deg iron head sbc's make max power at 32-34 always ended up around 37-38,, or more.. lol.
 

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Discussion Starter #15
Does the timing marks on the plugs look low?
the car did gain some going from 32 to 34 degrees.

I will order a set of NGK 7s with non-projected tips
Can't really tell from the pics, but I never had any built 23deg iron head sbc's make max power at 32-34 always ended up around 37-38,, or more.. lol.
Fwiw the heads are 200cc aluminum edelbrock etec heads with 64cc chambers.
 

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I don't know why you need colder plugs than -5s, the factory heat range. The car is not being circle tracked raced, where the plugs would see continuous high rpm operation...& more heat.

Plus, you have alum heads that remove heat more quickly than iron heads, so you would want a hotter plug to maintain tip temperature within working limits.
 

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Anything with more than stock power usually starts to get a colder plug. My slow ass SBC383 is 10.25:1 and makes about 400hp, it runs mint on NGK -7's. Old ass AFR 195cc aluminum heads. Never ever fouls a plug. What gain is there to running a hot plug? Trying to make-up for a bad tune?
 

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I don't know why you need colder plugs than -5s, the factory heat range. The car is not being circle tracked raced, where the plugs would see continuous high rpm operation...& more heat.

Plus, you have alum heads that remove heat more quickly than iron heads, so you would want a hotter plug to maintain tip temperature within working limits.
LMAOOOO
 

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Laugh all you want & show your ignorance.

If you read the OPs post, he ran the same with -5 & -6 plugs. From the description, it is a street car that gets drag raced occasionally. You want the hottest plug the engine will tolerate without causing pre-ign so that the plugs do not load up when idling/cruising.
 

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Laugh all you want & show your ignorance.

If you read the OPs post, he ran the same with -5 & -6 plugs. From the description, it is a street car that gets drag raced occasionally. You want the hottest plug the engine will tolerate without causing pre-ign so that the plugs do not load up when idling/cruising.
Actually, you want the coldest plug that will not allow fouling. That is, unless you have access to a system that can properly test for pre ingnition.
 
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