Spark Plug Recommendation

[kyle]

Hi all -

 

You know the phrase, "I've forgotten more about "X" than you'll ever know"?

 

Well, I don't know about the second part, but I do know about the first.

 

I've feel like I've forgotten what sort of spark plugs to put in my engine. CRAZY!

 

Since restoring/rebuilding eight years ago, I've put all of about 3000 miles on my Z. It's on the same set of plugs, and it seems that beadblasting them clean when they foul isn't a viable long term choice. (Don't worry, I clean them off before reinstalling, I'm crazy, but not that crazy.) Anyway, the plugs aren't fouled to look at now, but it's got a miss.

 

72 SUs/SM needles

GM HEI ignition in 76 dist

NGK wires

N42/mild port/polish

Cam is a 2002 (.480/274) IIRC

L28 +1mm

Flat top pistons/2mm head gasket, should be 9.0 or 9.5:1, can't remember.

MSA 6->2 header/2.5" exhaust.

Balanced internals and AL flywheel

 

Went to Kragen for a set of NGK BPR6ES, or maybe '7's, and they didn't have'm. Then it turns out they have different specs for L24 and L28E engines.

 

Any suggestions? Don't want to change to a different plug just because some outdated computer tells the underqualified counterperson what I should use.

 

Car sits a lot, gets driven spiritedly when it does though, but OTOH, lots of short little trips as well.

[wigenOut-S30]

the BPR6ES plugs should be fine for you but if you do go with the BPR7ES , I think the part number has changed.. From 2023 (old) / 5534 (new)

[kyle]

Thank you for the reassurance!

[PandaZ]

Dont mess around with ....s plugs (foul easier), at the very least use ....y (v-groove) eg: bp7ey or what ever heat range you need! (in NGK the higher the number the cooler the plug -> easier to foul)

 

Personally i originally used bp7e** for street to prevent fouling & bp8e** for club track events! (but my engine tune was alot more agressive than yours is)

Then found that Bosch WR56 work very well for both road & light track, as they are roughly an >8 ngk heat range, but use four electrodes and never fouled at idle, ever! (prior to Iridium plugs this is what i used once they became available! *cheaper than iridium too!)

 

Bp8eix or bp8edfi are excellent plugs from NGK! (i wont even go into ngk race only plugs)

 

 

 

*But for you setup BP6E would be fine! You could use 7 but only if you are using high rpm & not having fouling issues, i would also recommend iridium if you do choose to go colder!

**The fact your using carbs, mean you dont have to worry about the R in the code bp"r"6es, that just means resistor for efi stuff (not going into specific details)!

 

 

{i was a parts interpreter}

[z-ya]

For the street I would run BR6ES (non projected tip, resistor), or B6ES (non resistor). If you do track days you might want to run a BR7ES or B7ES although I've run 6s one my track L28 with similar specs as your without any issues.

[PanzerAce]

I run BP6ES plugs on my rebby motor and they run flawlessly as far as I can tell. part 7333.

 

Cold starts/cruising/etc (still gotta get places when it's 36 out) all the way to wailing on it when it's hot out (110+ ambient), never had a spark related issue.

[Tony D]

BPR(X)ES for the street or anything with electronics in it. That resistor plug is good for damping noise in the radio (especially AM) and keeps unshielded wires from picking up interference. Some systems (aftermarket) will pick up pulses on their TPS line making the engine think it's going WOT and screws the fueling all up.

 

On sandblasting not being a 'viable long term alternative' --- why not? When leaded fuels fouled spark plugs and tune ups were every 3K miles, people didn't think anything of cleaning regapping and reinstalling the same plugs. I still don't.

 

If the plug is working, it's working. If it's made of superior metals, and the edges stay sharp for good jumping off (no ground or center electrode errosion) why NOT re-use them.

 

If you got a miss, chances are much higher there is a wire breaking down than a plug that has been rendered unuseable. Though fouling says you got some other serious issues to deal with like overfueling. You can run a hotter plug to keep them burned off, but the real solution is to make the fueling proper.

[kyle]

As far as electronics go, I have the hall sensor and the HEI module, and a CD player, never listen to the AM/FM radio. Resistor or no?

 

I had one plug that would foul and just not fire, no matter how often I cleaned and gapped it. After much tearing of hair, I replaced the plug, and it was fine. That suggested that the plug could be bad internally, and not have an external fault I could fix. Buy that? Before that one plug, the plugs did not foul at all... and the set I have now aren't fouled at all. I think the fuel is pretty close, other than a minor seasonal tweak and adjustment.

 

The wires "were" new, and have very little use on them; can I just check resistance with a DVOM and see if they're all about the same resistance? Put it back together and run it in the dark, see if one's arcing?

 

Prior to pulling the plugs, I pulled the wires one at a time at the cap, and had a very large spark from each. No notable difference in the engine's running on the removal of any of them. But it's still got a miss!

 

Hard to tell at idle with the cam, it's fairly lumpy sounding. But once the throttle is opened, it's pretty obvious. Maybe the thing to do is to hold the throttle open so the miss is obvious, then check for power balance.

 

Haven't monkeyed with the carbs in a bit, I guess something could be up with them balance or adjustment wise, but my money's on the ignition.

 

Thanks for any clues or pointers, guys!

[kyle]

Hi again, hope everyone is happily sleeping off a turkey hangover.

 

Checked the plugs, 19/13/13/14/15/16 K Ohm 1-6 respectively. Cleaned the cap terminals, pretty corroded, regapped the plugs to 39 from 45 or 50, and still has a miss.

 

Then inspiration struck! Miss is most noticeable under a load... and sadly lacking a dyno in my garage, how to put a load on the old thing? OOH! How about this York AC, that sucker is a load and a half.

 

With that figured out, the #6 cylinder, though firing about as well as the others, wasn't pulling its weight. Swapped the wires, still #6. Swapped plugs, now #5 is out.

 

So, once again, I have a plug that looks good, doesn't carbon up, appears to fire, but just isn't. Whattya make of that?

[HowlerMonkey]

I've welded the electrodes together on the grooved ones while the exact same plug without the grooves lived 50,000 miles.

 

 

The moderators need to get rid of those resource hogging banners just above the posts.

[RTz]

The moderators need to get rid of those resource hogging banners just above the posts.

 

Those banners help pay to keep this forum breathing. If enough members donated, we wouldn't need them (yes, that was a hint )

[HowlerMonkey]

I mean that there should be some approval process before a banner is approved since the one commented upon ground my machine to a dead halt until it had fully generated and the text I was trying to type would show up about 4 seconds after I typed it.

 

First time I have seen that happen here.

 

Sadly, I forgot to get a description of it but I have noticed that any unstability and errors concerning viewing these forums seem to be related to certain banner hosting companies.

 

This is a relatively recent thing.......(about the last 7 months)

 

As far as donation, I am currently unemployed....which completely mystifies me considering my resume.

[kyle]

Sumbitch! Took it for a nice romp yesterday, filled it with gas, all was well.

 

Weather's decent today, figured I'd take it to work. About 2.5 miles into the 3 mile commute, #2 quit on me.

 

That's why I thought I should replace all six! Grrr....