Carbon Deposits On Head Normal?

[MerlinTheHapyPig]

Now, this is the first engine i've pulled apart so sorry if this is a bit of a newb question.

Refer to pictures, I'm wondering if this carbon buildup on the valves and top of cylinder is normal? (piston surfaces are like this also) I remember helping my dad rebuild a motor years ago, and it was nowhere near this bad. I'm trying to diagnose a possible problem with this rb20det I bought (it apparently had a misfire, but they couldn't figure out what was wrong with it).

Anyway, is this sort of carbon buildup a bad thing? The spark plugs were in similar shape, isn't this ment to mean it was running fairly rich?

anyway. like i said i don't really have a clue, but i'd like to have a rough idea of what's going on before i drop it off at the engine builder.....

[Craved]

hmm the RB30E i just pulled apart was like that, and mad flakes of it on the pistons

my RB25DET was heaps cleaner when i had the head off that, same with the pistons.. pretty much just discolouration not a coating like that.

[carl h]

that engine wasnt DRIVEN like it should have been, carbon builds up when you drive like grandma and dont give the old girl a good flogging once in a while.

when i pulled my head off my block nary a spec of carbon in the head and only a thin coat on the pistons, went well and never had a problem before i blew it.

proly misfired due to the massive ammounts of carbon buildup, hot spots and dieseling occur.

Edited April 8, 2006 by carl h

[GTRsean]

Yuo shouldn't granny drive skylines too much cos it packs em up over time. A decent drive clears the throat a bit!!

[R31Nismoid]

Could it be fuel choice aswell.

I've heard sopme comments around that constant use of the optimax down here in vic causes similar buidlup, not as bad... but more so than using Synergy/Ulti/Extreme

[Cubes]

I recently had 2 heads off an RB30e, one was on gas and perfectly clean, the other was rather dirty and on fuel, no where near as bad as that though.

Shall be interesting to see how the head on mine looks after almost 40,000km's. I drive it like a grandma 90% of the time.

[C_DawG]

Italian tune it.

Put it back together and bounce it off the limiter every gear.

[RB30-POWER]

Way to rich mixtures, nothing more, nothing less. (what caused the excessively rich mixtures would be the real question)

You can get upper cylinder lube/cleaner or carbon clean in a bottle you spray into the inlet manifold and it cleans the piston tops, valves etc, without having to remove the cylinder head.

Water also does a good job, but you have to be very careful, if you don't know what your doing as you can hydro lock it.

You don't want all the carbon in the combustion chamber at all as it can get rather thick in places and cause hot spots that glow and cause the engine to detonate.

You don't usually see modern engines in a state like that, because the ecu's control the injection so precisely.

But you get a backyard racer boys that fiddles with oxygen sensors, fuel pressure regs, injectors etc, without having a clue, you can get the above effect.

[rob82]

My guess would be a f**ked 02 sensor.

[carl h]

My guess would be a f**ked 02 sensor.

no way in hell a farked o2 sensor would do that, i didnt run an o2 on my car and had no problem with it.

im gonna guess perhaps bad gas and granny driving did that, but like i said eariler (and this applies to most if not all nissans) you have go give the girl a bit of a go once in a while to keep her happy.

[MerlinTheHapyPig]

intersting...

thanks for the replies, I don't know much about the dude who I bought the motor from, but i believe it was running an aftermarket turbo and higher than stock boost ~180-200kw or so from memory.

No idea if he granny drove it, I'll be curious to see what the head from the rb20det in my car looks like when i eventually blow it and have to change it, because i don't daily drive it, it's a dedicated drift car.

what would be the best course of action to reco the head?

[Busky2k]

Sounds like it had a 'rich' life. If you're running very rich on full throttle/high RPM, I cant really see how the 'italian tuneup' would help at all.