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Can't re-Member
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1,990 Posts
Discussion Starter #1
516ci BBC, N/A
8.75:1 Comp
AFR 305 heads, CNC chambers
Dart intake, 830HP carb
Hyd roller, 228/235 @.050, 650/603
5500 rpm max

Lake boat with a Bravo drive.

AFR says Autolite AP3935 or AP3932,
NGK cross reference's with the 3932 as a 10 heat range... cold??
the 3935 Cross references with a 7 heat range, closer to the BR6FS's I ran with the Iron headed motor.... Not sure where to start :confused: Shouldn't I be using a resistor plug??
 

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Bostick Racing Engines
Joined
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1,063 Posts
516ci BBC, N/A
8.75:1 Comp
AFR 305 heads, CNC chambers
Dart intake, 830HP carb
Hyd roller, 228/235 @.050, 650/603
5500 rpm max

Lake boat with a Bravo drive.

AFR says Autolite AP3935 or AP3932,
NGK cross reference's with the 3932 as a 10 heat range... cold??
the 3935 Cross references with a 7 heat range, closer to the BR6FS's I ran with the Iron headed motor.... Not sure where to start :confused: Shouldn't I be using a resistor plug??
NGK 4554 is a good place to start... may be a bit cold being a 8 heat range. Actually, 4091 would be the 7 heat range and may be more of what you'd need.
 

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steelcomp was here
Joined
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26,512 Posts
516ci BBC, N/A
8.75:1 Comp
AFR 305 heads, CNC chambers
Dart intake, 830HP carb
Hyd roller, 228/235 @.050, 650/603
5500 rpm max

Lake boat with a Bravo drive.

AFR says Autolite AP3935 or AP3932,
NGK cross reference's with the 3932 as a 10 heat range... cold??
the 3935 Cross references with a 7 heat range, closer to the BR6FS's I ran with the Iron headed motor.... Not sure where to start :confused: Shouldn't I be using a resistor plug??
I'm thinking the 32 is way too cold.
The 35 is better of the two.
Canfield always recommended a 3924 as a starting point...even a little warmer yet (NGK 5) and it always seemd OK. I like to run as hot a plug as possible and still have it live and do it's job.
 

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Registered
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4,549 Posts
Will to cold of a plug make it run alittle rich throughout the throttle or just at idle or WFO or any at all??
 

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Some guy
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3,610 Posts
I use some 3923 Autolites, couple steps colder than the stock 25, with no reported problems. I use them since they are readily available at parts stores, but I would run non resistor plugs if they were easier to get. Engine I just had on the dyno had NGK-7's, more compression and higher rpm than you are working with.
 

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Can't re-Member
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1,990 Posts
Discussion Starter #6
NGK 4554 is a good place to start... may be a bit cold being a 8 heat range. 4091 would be the 7 heat range.
The 4091 is the R5671A-7, which cross references with the 3935... :))THumbsUp

I'm thinking the 32 is way too cold.
The 35 is better of the two.
Canfield always recommended a 3924 as a starting point...even a little warmer yet (NGK 5) and it always seemd OK. I like to run as hot a plug as possible and still have it live and do it's job.
Another vote for the 3935's... I'll start with them.

I use some 3923 Autolites, couple steps colder than the stock 25, with no reported problems. I use them since they are readily available at parts stores, but I would run non resistor plugs if they were easier to get. Engine I just had on the dyno had NGK-7's, more compression and higher rpm than you are working with.
3923's are resistor plugs?? Is there a particular reason for running the resistor? I though it was just the radio thing:)Unsure... what about the type of ignition system?

sorry, it's my first set of Aluminum heads :D
 

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Premium Member
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5,115 Posts
I call NGK tech support when I don't know and that boy damn near nails it everytime. Not sure his name but the same guy has always answered the phone.
 
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