Spark Plug Suggetions

[Ricks82]

I'm looking for spark plug suggestions. I installed a 383 that sounds similar to the one in Shirley1978's post. 10.5:1 compression, aluminum heads, 456hp 464torque,(at the flywheel), Comp cams 12-214-4, 750 holley double pumper. The engine builder used Champion C57CX spark plugs, which I fouled like crazy. Recently I went to a NGK R5671A-8 which is a slightly hotter. (At least as far as I can tell.) I also took it to a local chasis dyno and had them re-jet the carb. (Went down a couple of sizes on primarys and secondarys) Right after the trip to the dyno the car went to the body shop. (to paint the gray Ecklers hood) When I picked up the car it was once again hardly running on six cylinders.:crap: I think that I am probably still running too cold of a plug, and am curious what anybody else might be using in similar applications. Any ideas would be great

 

[mrvette]

Plug wires/boots, I had a insidious problem with a intermittant raggedy assed REALLY rough idle due to header heat damage....think that SOB would show at night/dark...no no and HELL no, found it when the dirty muvva sparked in front of me as I leaned over the fender in total and complete frustration doing one of them smiley button head bangs.....

too boot it was combined with the water in gas problem....still a mystery about that one, must be a local issue.....anyway, I cured that wiring problem with a set of Jacobs ceramic boots, burn THAT, bitch...

I talk to my cars, projects, :bonkers::flash::amused:

 

[SmokinBBC]

So it ran good on the dyno after rejetting. What were the AFR readings on the dyno?

 

[Ricks82]

AFR of 11 seemed to be the goal of the guys at IDC (Illinois Dyno Center). These guys really seemed to know what they were doing, not to mention really great bunch of guys. :3rd: The car sounded good on the dyno. Made about 350rwhp.

 

[Ricks82]

:waxer:Missed that by a mile. I didn't think that I got a print out with all of the nunmbers, just the HP graph. (wrong again) I would have to say that 12.5 is about the average A/F ratio on the chasis dyno. Anyway the NGK R5671A-8 is the same plug that my nephew is running in his twin turbocharged mustang making way more HP than I am. (that hurts) If I understand what I've been reading more HP = colder plugs. Which makes me think that I could move up to a little hotter plug yet???

 

[SmokinBBC]

Just my experience with my BB which produces HP around 480 and Tqe around 532, 11 is too rich. 12.5 is good for making peak power when I need it. I have idle and cruise at 13.5+ where the engine spends most of it's time.

Those NGK's are racing plugs aren't they? Probably too cold a range for the street...no? Used for constant high RPM's, higher compression ratio and a hotter engine? Remember that for NGK, the higher the number the colder the heat range which is opposite US manufactures including champion.

 

[Ricks82]

The Champion Plugs that I was running directly crossed to a NGK R5671A-10. That's why I figured that going to the R5671A-8 had to be a move in the right direction. If I can get enough $$ saved up to change the gear ratio I'm sure that would help the motor alot. The stock gears in the 82's are rediculous. I'm planning on a set of 3:73 gears. I hope this brings the old girl to life. Coming out of the hole right now the car still feels like it has a tractor trailer hooked up behind it.:banghead: