Might as well add this. I started running OS P3's and my engine ran great. Never had a flameout. I switched to a Werks 6 when I ran out of P3's and experienced nothing but flameouts. Went to Werks 5 from there and all has been fine since. A few other locals that ran the 6 had the same issues.

Personally feel a plug will perform in relation to your tune . If you run a hot plug its easier its a great option if you need a bigger window. If your able to tune good running a colder plug will have its advantage especially with these CRE mills. I'm not saying you guys can't tune, I'm saying a colder plug has a smaller window its more prone to flame outs if your tune is off. I've been running the werk plugs from day one in humid and hot conditions without issues. I do go back and forth between 5&6 pending on the days weather.

I tried a Werks 5 and 6, and stock Novarossi plug on my buggy P5 and the idle wasn't as consistent, and the engine would flame, especially after the straightaway when the tune was fine. Put the OS P4 in, and it screwed in fine with no abnormal resistance, but I won't go back and forth between brands. I haven't had to touch the needles since I put the OS plug in, much more consistent idle and no flame outs so far! So my advice is, if your engine is running great, you should stick with what works for you, but if you are having engine tuning/flame out trouble, try a P4. It was a big difference for me, and my tune/temps were very similar with both plugs.

Ok, I'll take the risk and switch to a p4 plug.

My engine has a two stage idle like its rich but without moving the needles, I drive it for a few mins around the track and it comes of the track with a very high idle like its lean. Hopefully a p4 plug will fix this, I'll try to get it working better before I make the switch though.

Just remember OS plugs have a different taper if you swap back you will see light bubbles looking down into the plug cuase it wont seal

sounds like you could be rich on the bottom and lean on top!

The top is actually richer than I used to run it, I used to run it below flush, now its slightly above flush. Also the bottom is richer than what I used to run. Maybe I have an air leak somewhere but I will try a plug first.

Do you have a return spring for your throttle? When it comes in idling high see if goes away when you hit the brakes.

If the top is slightly above flush I think you have something else going on that's causing a problem, weather the tune balance itself, bad tank, bad carb boot, carb Loose carb or bad bearings. The plug might help but something else could be wrong. I've never seen a nova engine broken in that the high speed needle is above flush.

Yeah, its when I have the brakes on full, sometimes if I rev it while its high idling, the idle will drop back down but come back up.

Brand new rear bearing and a fairly new front bearing. I'll try the plug, if that doesnt work, I'll check my carb and seal it.

Alrighty guys. Heres the pics.

Nova #5 on the top OS P4 on the bottom. Yes differently tapered heads.


OS P4 in a Alpha head button made for plugs with nova's taper.


And the Nova #5 in the same head button. Can't tell a diffenrence huh.


The OS Plugs have a shallower taper but it still seals solidly on the buttons with the Sharp "Nova" tapers. I would be more worried about putting a Nova plug in a OS head button. Shallow taper with a sharp taper plug threaded in would lead to the plug pushing threw the plug hole slightly.

One of the problems I found a few years ago saw the Os plugs do not have the threads down as far toward the taper. (you can see this in your pic) A different brand plug in a Os motor would not seat because the threads bottomed out first because Os didn't tap the threads as deep. I just put the plug in a lathe and turned the first thread off. At the time I checked on a comparator the angle and the dia at the tip were very close.

Rex

my opinion is you cannot argue with what works for someone...if running a OS plug is the magic bullet someone needs to make a engine behave, then by all means run a OS plug.......... If you happen to be one of my customers and you do try a OS plug and happen to damage the button, just let me know and we will hook you up with a replacement button for very little cost.....With that being said, I have now seen multiple people swap between OS and Nova plugs with absolutely no leaking issues...........I cant say its the right thing to do, but I can say there was no leaking or any other issues...........different fuels, tuning techniques, environment, driving style can all play a role in what plug is ideal in a engine......

Neil will a OS button be different. I've serviced a few OS motors they swapped from a OS plug into a different plug causing a button leak. Would a OS button have different threads compared to a Nova button making a nova button less prone to leaks from different style glow plugs.

Jay, read what Rex(22racer)wrote a few posts above. I think he nailed it with the length of threads on the non OS plugs. That's why OS plugs work on other engines and other plugs don't work in OS buttons. It makes good sense.

we have run Werks plugs in OS engines...worked like a charm...then swapped back to OS plug without any issues whatsoever