Spark plug question

[Stu]

Was just about to order some replacement plugs and I’m now scratching me head. As usual…

Sometime last summer I replaced the plugs with hotter ones, now running NGK BP5ES. This was to see if it made a difference to engine temps.

Seemed to run better after that, but now having looked at them, looks like I’ve been running rich.

Did timing on the day and happy that was right, so not concerned there. Before I just get another set and assume it’s fuel mix, could the change in plugs have had any bearing on this? Would I be better going cooler?

[Dave999]

them look a bit grubby
is it running ok? in which case you are not a million miles off...i have conspired to create much worse on my own..

depends what you did before you took them out, so we don't know if its idle richness or at speed, mid rpm or wot richness

appears to be a line on the earth strap which is your indication of timeing and its at the bend this is good
the rest perhaps not, hard to see the second strap mark and the insulator is too grubby

this is very useful

https://fboignition.com/articles/sparkplugreading

in the summer your motor seemed a bit sick, we swapped to some little used or new ngks 5s and it ran better...reved out cleanly
BUT was that just new plugs or was it because we went closer to GOOD but not there yet.
I think we fitted something that might be considred ok for a standard set up... close to but not quite what was specified in 197?

only change 1 thing at a time is my only advice and i'd start with stuff that costs nothing
check timing and adjust idle mix
see if they get better after a decent 30+mph drive for 15 -30 minutes

Dave robbo posted up the idle mix and timing method on wolfmans vibration post

Dave

[Stu]

Cheers Dave

Yes, that was roughly my line of thinking on the plugs, it definitely ran better after we swapped them at the track, timing was done again after that and all was running nicely, so wasn’t sure whether replacing with the same and fettling mixture was the route, or try different plugs again.

[Dave999]

I can't remeber which way we moved

did you have 6s or 7s in there i.e 1 or 2 steps cooler

standard 383 plug is a J14Y or it seems to be a favorite for standrd motors
equiv NGK BP5S
Some seem to use N12Y which has BP5ES as equivelent same plug longer thread
we used this as a "most likley just fine" option after a bit of Blue/Pete/internet research

i.e we were in the ballpark

9Y used on performance motors like 340 with 10:1 or more CR champions heat range goes the other way

you have BP5ES that we dug out of of my box of spares, i got a good deal years ago when my motor was standard. the S means standard sized/type centre electrode E means extended so the threaded section is longer 3/4 inch, so it sits further into the chamber than the standard OEM specified plug

i think you have chamber much like a bucket and a piston half a mile down the bore so it made no odds from a piston/crunch point of view

i'm inclinded to say you just need to nudge it gently in the right direcion rather than go for wholesale change of plugs at this time.
they are not that honking and gummy as to be too far wrong. the car fires runs drives. in the past i have made it not the case with weber fiddling and inappropriate plugs.


Running rich OR failing to run ...... different
gentle carb fettlin... if it was idleing before you took the plugs out.. start there
then if its a holley i'm lost never owned one..... all diapraghms valves and holes in the side to see what dribbles out n that

Dave