Progress Thread Grover: Window motor replacement & OEM rebuild

HotFox said:

Bummer, The cratering look usually means water leak or way to little octane, that's Detonation.

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Or oil getting through and lowering it.

Its interesting that it is also the intake side.

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Piston is thinnest there. You can't see from the angle of the shot, but as that valve relief moves back down and to the right, it also shallows. The center of where it broke is the balance between getting close to the edge and still being deep enough. In other words, that's the closest point to the top ringland.

Note the peppering on the top flat of the piston, this thing did get run lean for a bit to cause the sand blasting or peppering look also detonation. I would pull the valves too, if you got some debris between the seat and valve it will need a valve job. Also it can transfer debris during over lap so you may have some other valves that had will need to be touched up. How is the turbine wheel? Any nicks? Might be hard to tell on the exhaust side without a full tear down and cleaning. So there was detonation, no doubt.

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I see the peppering. Didn't realize that was the marker of detonation. The stuff I've seen before were pitted more deeply. You can barely feel this stuff on the surface of the piston.

Well, up through pulling the head, the motor's run very well. There has never been the slightest hint of an issue... noise, rattle, vibration, smoke.... nothing. I just dismissed the oil usage as the rings having larger gaps since it's a high-boost car and figured that was my oil consumption issue. In fact, I wasn't even really looking for it. Just thought my buddies bore scope was cool and wanted to try it out. I'm just surprised that something like this would have no more noticeable a symptom than high oil consumption.

The rest of the pistons look good. Now that I'm looking for it though, I do see even slighter peppering at the top of #4.

I have no plans for a full tear down. I didn't even have to pull any accessories to get this head off. I had it off in about 3 hours, taking my time. In fact, because I'm moving in 3 months, I'm probably just going to slap it back together for now until I can get settled back at Fort Knox and find a nice machine shop that can help me out. I won't be racing or pushing it anymore, but it runs/drives perfectly fine, and as it has done so for almost 2 years, I'm not afraid of running it so I can move it around under its own power.

As you advise, I'll get the head checked out professionally. I might do that now, since it's already apart. To the naked eye, it looks alright.

@a91what

Here's the latest tune. Let me know if you see anything you'd consider too aggressive. This is my most aggressive (spark and fuel) tune to date, and it's run on a mixture of 91 + Torco that effectively brings the octane to 93.




Note from the most recent high-boost datalog from a few weeks ago below that I still have some significant leaning to do in the MAP-based transient tune. Peak boost was 14.1 psig, and it dropped to around 12-12.5 psi by the end of the run. The reason it goes that rich, I believe, is because the map-based transient adjustment is way overkill and it drops the actual afr to as low as 9.8:1 briefly. Then, the transient adjustment comes out and the AFR stays on the rich side of target (11.5:1). Timing should have been in the 15-16* range for this run. This is just an example of what I typically see. It has only ever been richer than commanded, which is the way I stay conservative.:



I know posting this will invite critique as though this was the cause, but that's ok. If I did do this, I don't want it to happen again. I'm certainly glad that I have never pushed to what I believed would be the ragged edge.

Dropped the head off with my machinist. I noticed a slight bit of light around the closed #4 intake valve. The other valves were in good shape. This piston's valves looked fine to my eye.

So, the machinist pulled the valves, and plans to clean the contact surface between valves and the ports on the heads up. He talked to me for a while about what he saw as he looked at the head. He does NOT think the oil is primarily coming from that ring land issue, because it's in all of the cylinders, which indicates it's from the intake or from the valve stem seals. If it were valve stem seals, I think it wouldn't be as consistent. So, looks like a turbo rebuild is in my future. @HotFox I guess I'll find out about that turbine, after all.

He also showed me how the keepers are wearing, and suggested I go through the entire valvetrain.

He said there was clear detonation in #2, but not in the others.

Here's an interesting learning point for me: if you zoom in on the picture, you'll see at the bottom of each cylinder there's a light smiley face that he thinks is piston rock into and lightly contacting the head. Apparently after coming to TDC, pistons can still rock in their bore enough to swing slightly and make contact. Never heard of that before, but what do I know? Wouldn't I hear this?

If I understand quench correctly, 3.4 stroke is 1.7 up + 5.4" rod, + 1.09" CH on the piston, which = 8.19". The paperwork I have says that the deck is also 8.19". So, the quench is also the thickness of my HG. The gasket is a Fel-Pro MLS (PN 1135) that is .041" thick. So, that's my quench, it seems.

MInor update. Thanks to Joe's detailed records, I have every number and spec on the pistons, but Diamond, in their infinite wisdom did not provide the piston weight. Therefore, I have to pull one out and scale it, before they can make me a replacement. So, I'm waffling between replacing the 2 pistons plus a couple more made for the future, and just replacing all of them with my preference for lower compression. At the moment, I'm leaning back towards just replacing a couple of Diamonds.

The head (passenger) has been cleaned up. 8 new valves, because some were showing uneven wear in the contact area with the head. .006" shaved to straighten it out. For now, I'm concerned with getting it moving again under its own power for my move in December. So, while I've bought a set of Fel-pro MLS replacements, I'll reuse the old ones for now, smooth out the minor piston damage slap it back together, and deal with the piston issue when I get to the new duty station early next year. I'll be careful and double check for contact, but I honestly believe I've been driving around like this for quite some time. Just getting it moving under its own power and not hot-rodding it is not going to worsen the piston damage on #3.

I pulled the trigger and ordered an Ed Curtis cam and spring package as well as all 16 valves, seals, retainers, and keepers. All of the valves and keepers were showing signs of wear on the passenger side. I'm sure the driver's side looks the same. Going back to Joe's question about why the cam swap, for some reason my higher lift, higher duration cam on the black car still drives nicer than my much smaller, very mild, lower lift cam on the blue car. Specifically, the blue car doesn't cruise w/o bog under 1800 RPM or so. The black car cruises at 1300. I have full control of both tunes.

After pulling the header off, the rubber in the motor mount on the passenger side has literally melted, due to the proximity of the head, I suppose. So, solid motor mounts will be going in. They supposedly have worse NVH, but I really can't tell the difference with the solids in the black car.

I guess what bothers me more than what I consider minor easily fixable damage, is that the whole situation really bothered Joe. Honestly, I think the repair is just a few hundred for pistons & rings. A couple hundred for replacement gaskets. A couple hundred on a cherry picker and engine stand, and a couple days of work that I enjoy, anyways. The cam and springs aren't mandatory. So, I look at them as an upgrade, not part of the repair. I have no idea what the turbo rebuild will cost, but I imagine that's just seals, too.

HotFox said:

If your hitting the head I would bet your under .035 or something is moving around in the lower end more then normal.

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First, I appreciate the knowledge dropped. Thanks for the good ideas. I think I'll pick up a dial indicator. I like having nice tools. 2nd, I'm not sure what you mean by moving around in the lower end. I haven't pulled the pan, and can't answer for the tolerances in the crank and rod journals.

Edit: valve counts... cuz I'm dumb.

lol. Well, I hadn't heard of that before. Eagle forged crank and rods. Supposed to be good stuff, but I'll keep that in mind for the lower end tear down.

Oops... haha. Hope I live that down some time soon. Right... I replaced all 8 in the passenger side head.

90sickfox said:

Putting it back together with .006 shaved on heads that already had valve contact with the pistons isn't the best idea in my opinion. Could end up trashing the valves again. If I were you I'd install a cheap stock engine just to get it moving until you can rebuild.

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Compression was still over 150 psi. The cam is small. I guess what's the point in being secret about it, since it's coming out anyways. It's a 218* ~550 lift intake cam. Pretty tame. So, I do not suspect a PTV issue, at all, though I will turn it over by hand before cranking to double check.

In any case, the machinist here did not instill any sense of confidence that he got the same valves that Ed will be sending. So, they're all being replaced on the main rebuild, regardless.