Hi guys.

I've noticed in 2-3 occasions, when I really push the engine, suddenly it starts to feel like there is a lack of power and a lot of smoke comes from the exhaust. It looks like it's white smoke. When I let off the throttle and if I drive with a little throttle, the smoke goes away soon and everything feels normal. This doesn't happen every time when I push it.

I have pulled the plugs, and all 8 look like this. I think this could be caused by cooling liquid. What do you think?
I'm thinking about bad intake manifold gasket. But all 8 plugs are the same. So it must be somewhere in the intake where all 8 cylinders could pull the fluid.
Any ideas and inputs are welcome.

This is the pic of the plugs

https://www.dropbox.com/s/8qtlijgvrm5rf9l/DSC_0108.jpg

... The green color is most likely an additive in the gas and not coolant ... the smoke might be from excess blow-by pressurizing the PCV vent tube on the Passenger side valve cover feeding oil mist into the throttle body and the intake ... this would cause a power loss as this additional air is not seen by the MAF sensor ... and oil in the combustion chamber will induce detonation causing the knock sensor and ESC to pull timing out .......

I will look into that possibility. But the smoke looked a lot more like it would be from coolant. Also, it looks like there is a little loss of coolant and oil level hasn't changed in 3000 miles.

I agree with C409. The green color on the ground strap is fuel.

Coolant in the combustion process will blast a spark plug completely clean... almost brand new looking. If there is enough antifreeze in the combustion process it will kill a plug and leave an oily, sweet smelling, slippery film on it.

From what I can see in the pics. The first one looks like it has some minor oil burn on it... definatly has some pre-ignition/detonation specks on it.

The second one has a few pre-ignition/detonation specks.

The plugs heat range is a little too hot for what your doing.... the color change on the ground strap should be in the center of the bend and yours is towards the plug case/body of the bend.... you can also see the "heat" on the threads of the plug case/body go up 4-5 threads and it should only go up 3 threads.

You could have too much overall timing in the engine or just too agressive timing map in the computer which could be contributing to what the plugs are showing.

Could be a combination of timing curve and oil in the combustion leading to what I see.

I can't tell you anything about the AF mixture because you can't see the correct part of the plug in your pics and I can see it's been idled around by the black ring on the plug case/body... idling an engine after a WOT pull kills any read you can get (in the context of AF ratio).

First thing I'd do is remove any PVC system going to the intake system and vent it to the atmosphere or better yet a catch can where you can monitor how much blow by your getting.

Second thing is I'd drop the plug heat range by 1.

Take it out and dog it a bit. Pull the plugs and see if your still getting those black specks on them.... if you are then take some timing out.
Will

Ok guys. Thank you for advice.
I'm about to change the plugs anyway, so I'll go with
one step colder heat range.
I'll also remove the PCV and see what will happen.

Hi guys.
Just to make an update. You were right. Color of the plugs has nothing to do with the problem. However, the problem was coolant getting into cylinders #3 and #5.
The reason is blown head gasket. But the reason for blown head gasket was this:

https://www.dropbox.com/s/h5vb88ck4t1lomj/DSC_0244.jpg

Arghhhh - bummer!!

Wow that sucks!

Actually, I'm glad that I've found this. I don't know if you remember, but I have built a new engine about 4 years ago. The reason for a new engine was that one valve broke in the old engine and made some serious damage to one of the heads and to cylinder block. So I've found a good used block and one used head. And ever since I have built this new engine, if I pushed it really hard for a longer period of time, sometimes a problem like I described in the first post would happen.
I belive that this head was cracked from the begining but the crack was probably smaller and it didn't make problems all of the time.

sorry to see

going to fix the head or go for new ones?

I will fix this one. I do plan to get new heads for a 383 that I'm slowly building but I think that I'll go with AFR 210's and those would probably be too much on current 350.

yea, 210s would be too much for a 350, unless you build it to rev to 9k RPM that is.