Here is the damaged head from one engine I hurt two years ago. Not only was the valve damaged, but the valve seat became exposed in the head, as some aluminum has melted away next to the valve seat...


http://i48.photobucket.com/albums/f2...d/Dscn2171.jpg

http://i48.photobucket.com/albums/f2...d/Dscn2168.jpg


Race gas and shaved-ground plugs took care of that issue for the next engine, though...

 

are you going to take pic's of this last engine that took a crap

 

can you post a picture of the shaved plugs?

 

Sure - here's one, right after a 13.2x pass..... Notice the anti-sneeze on the threads ??

http://i48.photobucket.com/albums/f2...3/Dscn1407.jpg

This trick and either Sunoco blue 104 octane or VP Racing Street Blaze 103 has done wonders for my constant 150-shot passes last season.
.

 

Maybe later -it's still in the car - I use it to move the wounded Max in and out of the garage while I'm playing Engine Man.

Once you've seen one hole melted through a piston crown, you've seen 'em all....


http://i48.photobucket.com/albums/f2...d/Dscn2238.jpg


Not much room at the moment, on "my" side of the garage. At least I share it with a 2004 Maxima (the Batcar)...

 

do you think there is anything you can change to save your next motor or is a 150shot just too much for the 3.0

 

I believe he blew this motor because for some reason he went lean. The 3.0 can handle 150 shot.

 

You are correct, sir. I ran that car all last season, through November, with the NX dual-stage set to 150-shot. (75-shot + 75-shot). Race gas and shaved-ground plugs FTMFW.

I finally take it out once this year, on July 11, and as soon as I sprayed the second stage - Flame On! - it went very lean and melted a hole in #4 piston. Bummer. I had opened both nozzles to clear the jets, put in 5 gallons of VP Street Blaze 103, eyeballed the fuel pressure, and mounted the 23/8/5/15 M&Hs before towing the Max to the local track.

Oh, well.

 

Did you figure out why it went lean? Also how do you know that it went lean?

 

Question. How come you melted a valve though? If it was a wet kit, shoudlnt it have kept a reasonable air/fuel to not cause detonation?

 

Every plug insulator went bone-white in about 600' I don't know why, yet...

 

Best guess - when ground straps begin to get so hot that they have a green glaze at the end, you are running on luck. When they get hotter and begin to glow, then you get pre-ignition and combustion temps go sky-high. This can melt valves - I've melted three - and blows the ground strap right off the plug. This has nothing to do with spark advance or air-to-fuel.

I have a collection of melted plugs with ground straps melted, blow off, or gone, and some iridium-electrode plugs with damaged and melted electrodes. Iridium melts at very high temps, but I warped some in the VQ30 furnace. I had one with the center electrode bent from heat and a piece of exhaust valve (the one in the picture) welded to the electrode.

Air-to-fuel was fine - probably a little rich, even - but glow plugs only work well in model airplane engines. After research, I went with the cut-ground approach (with race gas) and things were fine after that. 150-shot passes every time out - no problems except for traction.

Until July 11th - "if you ain't breaking somthin' you ain't racin'"

 

Interesting, Iv had a slight dusty green'ish color on my grounds, but I thought it was because of coolant (since i have blown hg).

 

That sounds like the "green glaze of death" to me - that's what mine looked like. That color does not photograph well. Does the glaze start at the tip of the ground strap and go down to where the strap curves toward the plug's threads? Does it have rings showing around the ground strap? If so, you're close to serious pre-ignition.

Straighten one plug's ground electrode, cut it off about 1/8" above the center electrode, round off the corners with a fine file (or your girl's nail file) and bend it straight over until almost touching the center electrode - and that's where you set the gap.

This removes most of the steel strap from inside the combustion chamber, and keeps the ground strap from glowing in the dark.

 

sorry my question was not clear

I know the 3.0 can handle the shot he ran it all last year, what I mean was with the nitrous setup it's self

do you think when running a 150+ shots it's a good idea to run a stand alone fuel system (aka run a 1gal tank, fuel pump and afpr) or a direct port setup some you will have less chance of 1 cylinder running lean

 

the local speedshop also told me about this trick so I can make my own, he said they sell plugs already made like this but they are 10buck each

great tip

 

[QUOTE=t6378tp]the local speedshop also told me about this trick so I can make my own, he said they sell plugs already made like this but they are 10buck each
QUOTE]


See post #4 in this thread for a photo of one.... Practice on old plugs until you get it right, then it's easy. The car runs the same during normal driving, too.


http://i48.photobucket.com/albums/f2...3/Dscn1407.jpg

 

SInce I don't know exactly what happened, I can't address this failure - but I use a Walbro 255lph pump, AERO FPR, a 300ZTT fuel filter, 5/16" tubing and distribution block, and always use straight race gas in the tank, 1/4 tank mininum. All real parts from the distributors - no Ebay here.

A direct-port system wouldn't change your odds. If the pump fails, pressure drops. If the filter clogs, pressure drops. If the FPR fails, pressure drops or raises.

What I don't have is a reliable fuel-pressure switch monitoring pressure, because I never found one I trusted. Adjusting them is guesswork. If I had a good one in place, then maybe it could have saved the motor. Maybe.

 

what I was thinking is that the fuel is not being evenly distributed thur all 6 cylinders and this is why only 1 cylinder went lean, and yes your correct about the pump failure, clogs or psi drops but a cylinder can still go lean with good psi without even distribution and the fpss will not catch it cause the fuel psi is good. remember the fuel is being sprayed at a single point before the tb and has to make it's way to every cylinder but with a single nozzle you have no way to control how gets to each cylinder, with a direct port setup this would not happen unless the fuel niod stops working cause each cylinder has it's own fuel nozzle.

just another way to look at it but I am still learning and could be wrong

 

Well - I suppose one injector could have failed, making that cylinder lean for the incoming N2O/fuel spray. Remember, the NX nitrous system mixes nitrous and fuel at the nozzle, then the mixed spray travels through the TB and down the intake manifold to all cylinders.

The mixture is the same for all cylinders, but it's possible to get unequal amounts of the N2O/fuel mixture into each cylinder. You hope the factory engineers designed the intake system to provide equal air distribution, since then you would have equal N2O/fuel distribution as well. A slightly unequal distribution would not make a cylinder go lean - remember, the engine pulls all its air through the same passages as the N2O/fuel spray. Reduced air flow into one cylinder would make that one rich, providing the injector was normal.

The direct-port system tries to avoid problems with unequal distribution with a more complex set of nozzles and jets, but if fuel pressure drops, you're still gonna go lean. Or if an injector fails, one cylinder goes lean.

In my case, I pulled the three front plugs right after I came back to the trailer, and stopped looking when I found #4 coated with motor oil. All plugs had gone from a light brown to bone-white, indicating a severely-lean condition. The oil says I have a ventilated piston - that, and running on 5 cylinders...

I'm gonna build up a 3.5, but I miss my 3.0. The build will take a while, and I've been thinking about slapping another "junkyard dog" 3.0 in the car for fun . Time will tell.

 

I decided to tear down the 5-cylinder 3.0 from last year. One piston really had a problem.




More views of the same piston:
http://i48.photobucket.com/albums/f2...c/DSCN0087.jpg
http://i48.photobucket.com/albums/f2...c/DSCN0084.jpg
http://i48.photobucket.com/albums/f2...c/DSCN0078.jpg
http://i48.photobucket.com/albums/f2...c/DSCN0077.jpg
http://i48.photobucket.com/albums/f2...c/DSCN0076.jpg
http://i48.photobucket.com/albums/f2...c/DSCN0074.jpg

and the combustion chamber: ( note the cut-ground plug )

http://i48.photobucket.com/albums/f2...c/DSCN0080.jpg


Ah, good times...

 

damn

 

wow . I wonder what mine looks like.

 

Ooooh, I've got one of those pics also.......

350Z motor that I rebuilt, owner thought it would be ok to hold a 100 shot on the highway for "oh I dunno, between 10-20 seconds"

 

Funny, same thing happened to me on the strip....



Heh.....

 

Wouldn't water/alcohol/methanol injection help with detonation problems? I'm considering going with water injection for my 100 shot, why not for a 150?

 

Well - unless you're having detonation problems now, how would you know it helped? My problems went away once I cut back the ground straps on the plugs and went to straight race gas.

Dunno who on here have used water/alcohol alone when spraying - they would be the ones to answer you. Good luck....

 

I am currently spraying a 100shot without any problems but I am using 2step colder side gapped plugs thou with 100octance gas.

soon as I get some times with the 100shot I'll be stepping it up to a 125 then 150 and the only thing I plan to do is run a richer a/f ratio each time I go to a higher shot

 

Hmm, looking at that first pic, I'm wondering if it wasn't debris that caused that. I'm not seeing the typical swiss cheese or moon-surface that you typically see in aluminum with detonation. the valve has sharp edges more typical of metal fracture, not smooth edges from melting.

I'm wondering if that wasn't a valve that tried to close on a small screw (or broken off/ burned ground strap) and then was 'forced' shut by the piston, thereby shattering one small part off the valve and mashing it into the head..


nonetheless, it's still gruesome. ouch.