Yellow Bullet Forums banner

1 - 18 of 18 Posts

·
Registered
Joined
·
1,682 Posts
Discussion Starter #1
Before i buy a pile of these i was wondering your thoughts on this plug R5671A-9 and for the record my engine for whatever reason when it was naturally aspirated hated NGK plugs...

321" SBF
10.5:1
E85 Blow Thru
Twin 66/73's
20-25psi
950-1050hp i hope

Thanks
 

·
Registered
Joined
·
426 Posts
I run that part number in my 388 sbc basically same deal no issues except mine is 9:1 comp. I run -9 up to 22psi and -10 above that. Make sure they’re legit NGK’s. There’s China copies out there and they are junk.
 

·
Registered
Joined
·
1,682 Posts
Discussion Starter #3
i see they are $1.54 on rock auto.... not sure how to tell if they are legit
 

·
Registered
Joined
·
1,816 Posts
On e85 i dont see why you would want anything that cold. I run 7’s in my bbc up to 20 psi so far and we have run 7-8’s in lsx turbo cars in the mid low 7’s 1/4 mile on e85.
 

·
Registered
Joined
·
47 Posts
I don’t know know anyone running anything but 7s. Either a 5671A-7 or a BR7EF. I ran either of those in a 10.5 to 1 6.0 LS with S467 Borgs for two years on 40lbs.
 

·
Registered
Joined
·
47 Posts
I started with 9s when I started out with a blow through on E85 before I switched to Holley Dominator EFI. I was glad when the engine showed it liked 7s because I found out that even E will foul a 9 quickly.
 

·
Registered
Joined
·
1,682 Posts
Discussion Starter #8
Well that’s why I asking... I really have no idea what to run. I used to run a 3924 naturally aspirated in this engine and 11.5:1 pump gas. If any of that info helps
 

·
Registered
Joined
·
426 Posts
On e85 i dont see why you would want anything that cold. I run 7’s in my bbc up to 20 psi so far and we have run 7-8’s in lsx turbo cars in the mid low 7’s 1/4 mile on e85.
I’ve always been told that too but I’ve never had an issue or gained anything going any hotter. Always ran whatever heat range needed to prevent fouling. Never fouled a plug ever and I can street drive the hell out of it on the same plugs and have zero issues.
 

·
Registered
Joined
·
5,660 Posts
-7 for street driving and -9 at the track. If you are pretty easy on it street driving a -6 is not out of the question. I run -10's on methanol but it doesn't foul like gas and E-85 does. I haught -10's as cheap as $1.27 but its rare to see them that cheap. I bought over a case the last time I saw them that cheap.​
 

·
Registered
Joined
·
16,437 Posts
I run NGK Iridium 8 plugs on my SBF twin turbo setup. They last forever on a street/strip car and the gap doesn't open up. The current set have been in the car for 2 years and have 4000 street miles and just over 100 passes. The car went 8.69 at 166 on 24lbs boost last week with those plugs on E85.

It helps a lot to run the engine lean while cruising, I usually see 15.0-15.8 AFR until it gets near "0" vacuum. I currently am running COP using the 1A coils but I used the same plugs for years with a distributor ignition system and running C10-C16.

By the way, these are projected tip plugs which are also fine despite the current thinking by many that extended plugs are not good for high powered cars. Years ago I was told by a NGK representative that the recessed plugs are designed for engines that have piston/plug clearance problems and extended tip plugs are not prone to pre-ignition or detonation if they are the correct heat range which is true for any plugs.
 
  • Like
Reactions: Orr89rocz

·
Registered
Joined
·
16,293 Posts
I run a -7 on the street (shell 91 and 7 psi spring pressure) and a -8 (gapped at .023) at the track on C16 and running 8.70's @ 23#.
 

·
Registered
Joined
·
16,437 Posts
I run a -7 on the street (shell 91 and 7 psi spring pressure) and a -8 (gapped at .023) at the track on C16 and running 8.70's @ 23#.
Unless you like changing plugs, you should consider getting a set if Iridium 8 plugs and just leave them in.
 

·
Registered
Joined
·
1,682 Posts
Discussion Starter #17
Well as cheap as they are I will get a set of 7,8, and 9’s and just see how they hold up. I will start with the 9 and if they look to cold or foul out I will go to the 8 and so on.
 

·
Registered
Joined
·
16,437 Posts
How is reading those?
If you're trying to tune a combo use the cheap NGKs since you need to use fresh plugs to get a good reading and it may take several iterations. The Iridium plugs will show the same info as a regular plug but honestly, I have never used plug readings to tune my combo. I only look at the plugs for signs of problems. The plugs in the engine right now went in 2 years ago and I haven't looked at any of them since even after all the street miles and runs I've put on them.
 
  • Like
Reactions: tempname
1 - 18 of 18 Posts
Top