Six_Shooter's money pit and time vampire... v.240Z

[Guest]

Good thoughts.

This (green) block was the one that had the headgasket blow, I swapped bottom ends at the time since I had another bottom end, and really didn't know the history of the one that was in the car.

The head gasket blew on #3 and while that rod did suffer damage from this, it was an innocent casualty from what I've been able to determine.

The pistons in the green block were not original to the block. After I had the issue with the ignition module going haywire and spinning the engine backwards, I swapped it out for the green bottom end, when it also got a cam upgrade and new bearings, since there was a sound while cranking I just didn't like, but couldn't find the source of it. Maybe that source was piston #4, but I didn't see anything when I looked them over. I didn't want to use these pistons, but I found one piston from the original set for this block with a broken ring land between the top and middle ring, so I swapped all of the pistons.

The car has been a little rich under boost for the last few weeks, because I scaled the fueling parameters to have a bit more head room in the VE table, where I was maxing out the VE. I was getting it closer to where I wanted, just didn't get it there. Every time I've pulled plugs on this engine they always look decent to slightly rich, depending on how long after pounding on it I shut it off.

[Guest]

Not enough ring gap, looks like. Detonation severe enough to break off that much of the ring land would show up in you cylinder head combustion chambers, or on the undamaged area of the piston as little pockmarks. What did you open the rings up to?

Keep in mind hypereutectic pistons require a much larger (20 to 30 percent, in many cases) top ring gap compared to a non-hypereutectic piston. The top rings on my 3.4L are gapped at 0.028", compared to 0.018" that would normally be fitted to that engine. All because I'm running 3400 hypereutectic pistons.

Ring gap was around .022" IIRC, I'll have to go back over the formulas again (or measure them) but they were on the large side of what my engine builder friend recommended and what I found from other sources, I don't see this as a ring gap issue, I just see it as the piston getting pounded on for months well beyond it's designed stress limits. With how there is literally nothing of the skirt left on #4 I would have to think that the skirt/bottom of the piston failed first and then because the rod pulled out of the piston, when it came back up it pushed what was left into the head causing the ring land to break, and then causing the rod to fail, which just snowballed from there.

I've only had a couple of times when I got some detonation, because I tried something different with the tune, and immediately went back to what I was running previously.

[Xnke]

Again...not enough top ring gap. Hyper pistons don't use normal piston ring gap rules, and boosted hypers even less so.

I don't think the lower part of the piston failed first, because you have two pistons with ringland damage, of the same type. I have never seen a piston break the top ringland from being slapped against the head-the top ring will just not allow that much compression there.

To be sure, you'll want to go over all the other pistons with a picky eye...look for cracked ringlands on otherwise undamaged cylinders.

Try to get photos of the ring gap faces...if they are shiny, they have butted together. If the ring gap was big enough, you shouldn't see any shiny or fretted marks on them

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[Guest]

Again...not enough top ring gap. Hyper pistons don't use normal piston ring gap rules, and boosted hypers even less so.

I don't think the lower part of the piston failed first, because you have two pistons with ringland damage, of the same type. I have never seen a piston break the top ringland from being slapped against the head-the top ring will just not allow that much compression there.

To be sure, you'll want to go over all the other pistons with a picky eye...look for cracked ringlands on otherwise undamaged cylinders.

Try to get photos of the ring gap faces...if they are shiny, they have butted together. If the ring gap was big enough, you shouldn't see any shiny or fretted marks on them

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It's MORE than enough ring gap, think what you want, but the ring gap was plenty. I have one piston with ring land damage. The one that I mentioned in my previous post was a different set and different part of the piston and also had stock ring gap when I ran them. Considering that the contact pattern in the head shows a clear indication that the ENTIRE outer ring (top) of the piston tells me that it didn't fail first. That the entire pistons was pushed into the head, and not parts broken off that got caught.

I've ran hyperutectic pistons with less ring gap and similar levels of boost on similar bore engines and never had a ring pinch. I don't see how the piston material effects how the ring reacts to heat. *facepalm*

I'm replacing the rods and pistons with aftermarket parts now anyway.

[Guest]

I had bought a used 3.4 iron head pushrod engine long ago that had been rebuilt. No idea on the pistons used, or ring gap. I boosted that baby with 10-12 lbs of boost and a 100 shot on top of it. never had a ringland issue in that engine. Bent 2 rods though. 500+tq at the crank. Detonation will destroy ringlands fast. if you posted pics of tht I haven't looked at them yet so sorry if it wasn't detonation.

I say move to a lz4 or lz9 engine instead of a rebuild. Mars seems to have good luck with his on about 550-600 hp on stock internals. you already have a cam too, that you can swap into the 3900 if you wanted. plus the lz4/9's are now pretty cheap, and you can get them with low to medium miles for under $800. Thats the cost of forged pistons for a 3400.

[Guest]

I don't see any signs that detonation had caused this, there's no pitting or silver flakes that would indicate that was a problem.

I've considered going LZ9, and I can get as many complete as I want for about $225 CDN each, but I'd still be rebuilding it with aftermarket parts, because I'm just at that point I don't want to screw with stock internals anymore. I've read about and kept my eyes on a few LZ9 swaps and builds, and it just seems that the cam is a real issue. Going to bearing spacers and a standard cam just seems like leaving something out. Like there's something being left on the table. Like getting a piece of apple pie on your plate, and even on your fork and then not eating it. I don't want to mess with VVT right now, even though there's a few options to control it (VVTuner, MS3X, etc), there seems to be some debate on exactly how it works, and I really don't want to spend time on figuring that out right now. There doesn't seem to be much improvement available in the heads. I'd have to completely rework the belt drive and a few other challenges that would likely come up. Overall I just don't see any appreciable reason to go to an LZ9 over using an LX9.

The LX9 will have plenty of potential for what I want to do. It already has more power than I can really use, but my plan is for more... along with plenty of suspension changes to actually use it. If I ever need to go bigger than the LX9, I don't think just a displacement increase will do it, I think it'll have to grow by a rather large cylinder count as well. I have access to the engine I speak of, with a couple hair dryers hanging off of it, but I don't have the $10k or so it will cost me to get it in my hands, before even fitting it to the car. That $10k is a SMOKING deal too. I know of only one other 240Z with that engine.

So, I'm sticking with my plan of going with a built bottom end to handle the power I want to make, both peak (dyno queen numbers) and everyday pound on it power.

[34blazer]

If Turbo Buicks can push a 3600 lb car well into the 10's with a stock long block, or even champion irons (which flow significantly less then LX9 heads) and get into 9's, then I think there should be no problem with the LX9 making good power to get those same numbers in a chassis that weighs far less.

Bigcheese and I were talking about options for a custom billet cam for the VVT, but most grinders won't touch it for less than a Grand, and thats a big IF, they want to even try it.

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[Guest]

Exactly. This car will not get a cage, so running 9's really isn't an option, but it would be nice if the potential was there. lol I plan to make a bolt in roll bar so that I can at least run low 11's or 10's once I get that far, but because of ridiculous insurance rules around here I need to make it a bolt in to be able to remove it when I'm not at the track.

That was another reason to not go LZ9, as you were having issues getting a cam made for it, and I just don't want to have to go through that to get a cam made for it.

[Guest]

I don't see any signs that detonation had caused this, there's no pitting or silver flakes that would indicate that was a problem.

all my plugs were fine when I removed them, but I could actually hear the detonation happening even under part throttle. Had a bad tank of gas which ruined this motor.

bustedpiston3.JPG

ringland busted off. Everything else looked just fine.

I just ordered a cam for my 3900. I am using bearing spacers. I don't expect to leave much on the table at all. The 3900 has a strong bottom end from factory, and even with the bearing spacers, you can put in a cam with over .600 lift at the valve without P to V contact. I might be wrong, but I don't think thats possible on stock pistons in an lx9. Granted you are going custom forged so you can have valve reliefs cut for that and WOT tech store will make pistons with that feature.

stock lz9 heads flow about 232 at .500 lift according to a link here, and I am sure Ben flowed a set too. Ported flowed 250ish at .500 lift. I will have to go back and look but I don't think the lx9's are near that. Maybe 230ish cfm when ported?

lz9 can do a 75mm tb. I think the lx9 is stuck at 65mm with a ported upper plenum.

I got my 8k mile 3900 for $800. Not a steal but a decent deal. I see lkq in canada has them for like $500 for middle mileage like 40-50k miles. Saw it on ebay. I prob wouldn't bother with rebuilding with that mileage. the engine didn't come in sports cars so probably not abused

yes swapping to the more displacement wont' be a direct bolt in, and it will take some ingenuity with the front drive belt, so its understandable not to want to go that route. you already got the lx9 in so sticking with it limits additional fabrication. My build requires fabbing with either engine I choose, so I figured might as well go 3900.

[34blazer]

http://www.ebay.com/itm/Chevy-60-degree-V6-Billet-Crankshaft-and-Rods-/121720226360?hash=item1c57174238:g:OnoAAOSwu4BVvkUw&vxp=mtr

[Guest]

http://www.ebay.com/itm/Chevy-60-deg...BVvkUw&vxp=mtr

LOL, wouldn't work for me, and besides the LX9 crank is already a forged steel crank, which should be plenty strong enough for my goals. I also don't want to de-stroke my engine longer stroke = more torque, or at least easier to make torque.

all my plugs were fine when I removed them, but I could actually hear the detonation happening even under part throttle. Had a bad tank of gas which ruined this motor.

[ATTACH=CONFIG]8770[/ATTACH]

ringland busted off. Everything else looked just fine.

I just ordered a cam for my 3900. I am using bearing spacers. I don't expect to leave much on the table at all. The 3900 has a strong bottom end from factory, and even with the bearing spacers, you can put in a cam with over .600 lift at the valve without P to V contact. I might be wrong, but I don't think thats possible on stock pistons in an lx9. Granted you are going custom forged so you can have valve reliefs cut for that and WOT tech store will make pistons with that feature.

stock lz9 heads flow about 232 at .500 lift according to a link here, and I am sure Ben flowed a set too. Ported flowed 250ish at .500 lift. I will have to go back and look but I don't think the lx9's are near that. Maybe 230ish cfm when ported?

lz9 can do a 75mm tb. I think the lx9 is stuck at 65mm with a ported upper plenum.

I got my 8k mile 3900 for $800. Not a steal but a decent deal. I see lkq in canada has them for like $500 for middle mileage like 40-50k miles. Saw it on ebay. I prob wouldn't bother with rebuilding with that mileage. the engine didn't come in sports cars so probably not abused

yes swapping to the more displacement wont' be a direct bolt in, and it will take some ingenuity with the front drive belt, so its understandable not to want to go that route. you already got the lx9 in so sticking with it limits additional fabrication. My build requires fabbing with either engine I choose, so I figured might as well go 3900.

Well, it's a good thing I'm not relying on only the plugs to see if there was any indication for detonation... since I have the engine apart I can look right at the pistons and heads and see no indication that there was any or much. Like I've already said I know I got a bit when I tried something with the tune a few weeks ago, but went right back to a known working bin. I stand by my thoughts that the skirt of the piston failed first, and then caused the piston to hit the head with the entire face of the piston head as indicated by the mark on the head, and then it snowballed from there. The damage and tell tale signs just point to this and not the ringland letting go first.

My comment about leaving something on the table was not about overall power, but overall functionality of the engine. It's like buying a new car and then pulling out the automatic climate controls, because yo'd rather have manual controls, or buying a new high end home theater system and throwing the audiophile quality center channel away to use an old crusty '70's dual cone instead because that's what you're used to, or buying a new cell phone that has upteen billion megapixel camera, just to set it to the lowest or next lowest quality setting, it just doesn't make a whole lot of sense to not take advantage of the new features. As I said I just don't have the time, to get into that nor the money for a custom cam to take advantage of it. And every build that I've seen that uses a locked out cam has been less than what I'd consider stellar results. I know what I can do with the LX9 and it's more conventional cam, without removing potential features that could improve economy and/or power.

You're also not getting it... I ALREADY HAVE MORE POWER THAN I CAN USE, so why do I care about using parts or an engine that can produce even more? I don't. My builds are never just about peak power, in fact I usually never go for peak power, I try to maximize the area under the curve to be more fun to drive, more efficient and overall just more enjoyable. If that means giving up a few peak HP, fine. I'm also done fucking around with stock bottom ends, I'm building this engine one more time, barring me doing anything really stupid that causes it to blow up, but the plan is to build it for some far off extreme goal of mine now, so that I don't have to do it again later.

I already had to cut valve pockets in my pistons for the cam I'm running, so I will need those added to the new pistons, which will not be from WOT-tech anyway, I'll get them through my machine shop so that I know that they are exactly what I need and want. My machine shop has over a century worth of experience between the father and son that work there and have built everything from oddball stock tractor engines to large V8s that make 4 digit HP and live through extreme conditions, so I'll use their advice and suppliers.

The throttle body size is irrelevant since I can just modify the upper intake if I need something larger, or make a whole new one. I'm not about what can bolt together, I'm about what I can make work and work the way I want it to, that should be obvious from this thread alone.

I already said I can get an LZ9 for $225 complete if I wanted, and pretty much as many as I want, I've considered it a few times. There's more cons than pros for my application. The LZ9 is just not going to happen at this point, it's not what I need, it's not really what I want, and will just add to the cost of my build (in more ways than one) for absolutely ZERO benefit.

I want the car to be back together for the spring and going with the LZ9 wouldn't allow that to happen due to all of the extra costs and time involved, which again will gain me nothing. I have enough planned changes and upgrades to the car for the winter as it is, some are engine related (since my hand is now forced lol) and some are to utilize the power, and some are cosmetic.

[34blazer]

Wish I had the money for that crank/rods combo. Twins revving at 8k and I would crank the boost. lol

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[Guest]

Wish I had the money for that crank/rods combo. Twins revving at 8k and I would crank the boost. lol

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Yeah, it could be a lot of fun.

I did at one time consider de-stroking a 3400, for a short stroke 3.1 (3100?) but decided that torque was more what I was after. LOL

[Xnke]

Post a photo if the ring gap faces. I bet they are shiny or burnished.

You think I am trying to be a know-it-all, but honestly I just don't want to see you have to put a third engine in this thing.

When ring ends butt, they trap the ring in the bore. Sometimes the top of the piston pops off, sometimes it rips the rod out the bottom. Either is consistent with your damage pattern.

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[Guest]

Post a photo if the ring gap faces. I bet they are shiny or burnished.

You think I am trying to be a know-it-all, but honestly I just don't want to see you have to put a third engine in this thing.

When ring ends butt, they trap the ring in the bore. Sometimes the top of the piston pops off, sometimes it rips the rod out the bottom. Either is consistent with your damage pattern.

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I'm going to tell you ONE more time, this was not a ring gap problem. The ends of most my rings are still somewhat shiny from when I gapped them in the summer. There are a couple that are only a slightly darker shade, but also show no signs of touching. The file marks are still there. The ring gap was plenty for what I was doing, end of story.

So what you think you know about my engine failure you do not, end of story.

I know what happens when rings butt up against each other... it's not hard to figure out *facepalm*

I followed the advice of my engine machinist, who like I said previously between him and his father have over a century worth of experience, and he's never led me wrong previously.

These were stock pistons that were pushed far beyond what they were designed to do with many no load (due to lack of traction and steep gear) revs, and a couple instances of less than optimal operating conditions, a couple of times of detonation and spinning in reverse due to a bad ignition module when coming to a stop, which means it reversed direction very quickly, all of this is what I believe was the ultimate demise for this set of pistons. I probably should have looked at them more closely when I had them out in the summer. It doesn't really matter, because as I've already said, I'm not fucking around with a stock bottom end anymore, and will be built to handle the loads and RPM I plan to use this engine with.