[Dadic 78]

Anyone here running O.S. #8 plugs ever have issues with them? I've run this plug in most of my vehicles. Currently I'm running my Losi XXL (454 engine) and I'm going through them quite quickly... In fact, I had one only last about a tank of fuel earlier today...

The filament in the plug that only lasted a tank was pretty "beat up" looking when I removed it. Bent upwards, towards the top of the plug. Any thoughts on what would cause this?

Just looking for as much info as I can get on plugs (the O.S. #8, in particular) and any possible substitutions for my 454.

Thanks,
FD

[Guest]

you mighty be too lean.....

[Michael_Lambert]

I have been running the OS#8 plugs in my 8ights 454 motor as well and never had an issue.

Running the engine around 220 degree's and i think i got pretty much a gallon out of the last one and have about 3 tanks on the latest one.

[Dave Henry]

I would suggest you pull your engine,remove the bell and then see if here is any vertical or horizontal play in the crank that would indicate worn bearings. A little in and out play is normal but any other play usually means bad bearings that could be shedding small bits that will kill plugs even with a very rich tune.

As others have said o.s. #8 plugs are normally very reliable.

Edit.. In a losi mt you can remove the spur gears and clutch bell without pulling the engine.

[Gump]

I'll second what Dave said - when you blow plugs that quickly its a sure sign of excessive play in one of the following components:
worn crank pin
worn bushing at the bottom of the conrod
main bearing (the larger one) with excessive play

When any one of these components or a combination of them has excessive wear it will cause the glow plug element to blow under compression. It still stays lit while your engine is running because the broken piece is still red hot. when you stop the engine, you can't refire because the element is broken and won't complete the circuit when the ignitor is applied.

[Dadic 78]

Thanks for the input guys. I'll inspect the engine this weekend for excessive play, and/or wear.

Another thought... Typically I buy my plugs from my LHS. The plugs I am currently using I purchased on Ebay (six plugs, $25) so the price was right. I'm thinking maybe these plugs were "factory defects" of some sort... Anyone heard of this type of thing happening?

[Gump]

never heard of it. i ran #8's for a long time and they were always good to me

[MikeZ]

One other thing to consider(not really related to your issue though) is that an OS plug is 1 thread shorter than a full length plug. It doesn't sound like a lot however it will give you less compression than a full length plug.

Please keep in mind also that this effects OS engines too so if you decide to use a standard plug and not an OS(not sure why) it will give you more compression and even possibility of not enough space from the piston.

If you like OS plugs I would consider an R5 for a high end engine. The #8 is great for airplanes but not the best for high performance revs/temps, in my experience.