lee101315

Prior to installation of the fresh turbo (the old one had a lot of shaft play), I rebuilt the cylinder head. This included pressing in new valve guides , cutting the valve seats, lapping the valves, and doing a port and polish (mild, mirror finish) on the intake ports. The cylinder head was decked only to clean it up, and a Cometic head gasket was installed.

So now that I had the head out, I decided it wouldnt be much more trouble to remove the oil pan and install some fresh piston rings and rod bearings. The oil pressure was pretty good at idle, so I decided there was no reason to pull the motor and change the main bearings. All O rings in the exhaust system are new, and all vacuum lines were changed. Of course, while removing the exhaust there were few setbacks. The O2 sensor wouldnt come out. Eventually after heating it up with the torch, it did come out...but the O2 threads stayed in crossover...DO'H! For all the guys who remove the crossover pipe on the floor in your driveways, I give you DIY guys props. I would rather light myself on fire and burn slowly to death than remove that pipe again, and I am an experienced tech with access to a shop.

I did bypass the cycling valve and install a manual boost controller. The car has a set of Autothority chips ( temporarily ). I also lapped the valve on the wastegate and preloaded the spring 6mm. Along with this, I swapped in a k26/8 turbo with almost no shaft play. For all you guys talking about the "bottle neck" in the exhaust and swapping in a 3" downpipe.... The real restriction is in the #6 hotside. The car runs much better with a #8 hotside (less backpressure pre turbo) and no cat.

500 miles later, the turbo needle finally gets leave the vacuum side of the gauge

If I set it to 15 psi, it will drop to 13 psi by 6000rpm. If I want 15 psi at 6000rpm, I have to crank the **** to 18~19psi (also scrambling for traction in 2nd gear at full boost). The car pulls much harder with the#8 hotside, and the turbo hits a lot harder.This is with fresh piston rings, zero exhaust leaks, a pretty fresh turbo and a good factory wastegate. I will leave the boost set at 15psi until I can monitor A/F ratios (coming soon).

BlueRiver86

Cool. What are you planning for chips?

Waterguy

I have done the rod bearings without doing the mains twice now (different 100k+ mile engines.) If I were to do it again, though, I would pull the engine and do the main bearings "while I was in there." So much quicker to pull the engine, do the work and clean everything up properly. Also, the main bearings do wear, especially the thrust bearing.

No big deal. I have done that three times now, and can tell you that it is much easier on a concrete driveway than a gravel driveway.

They run much too rich. Change them out ASAP.

Amen to that! Wait till you invest in a real wastegate. 15 psi by 3000 rpm with a K26-8, a Tial 38 and no cat.

special tool

I agree.
I have NEVER seen a thrust bearing that wasn't light brown at least on one side.

PorscheDoc

ditto

95ONE

person motor; thrust bearing. +1

lee101315

I am not sure yet, I dont like to do things twice. The obvious choice would be Vitesse chips and a Vitesse MAF, I was also thinking about doing a piggy back... I definately have some planning to do.

Why didnt I remove the motor? I didnt plan to go into the block... I started out just wanting to change the headgasket because I was burning antifreeze and pressurizing the cooling system (No wonder 2 of those pistons were carbon free). Next thing I knew, I innocently took the head apart to check the valve guides... and since I changed the valve guides and seals... it would be a shame not to freshen up the piston rings (the oil pan was leaking anyway, so why not?)

You guys are right about the thrust bearing likely having some wear, but honestly... what do you expect? Any car with a manual transmission will have some wear on the thrust bearing (exception being the rotary engine), and its no big deal (unless its a mitsubishi 4g63t ....). Another good reason not to hold the clutch in while waiting at redlights?

So which way were you guys talking about the main bearings wearing out on these engines? Were you guys noticing excessive crankshaft end play ( worn thrust bearing ) or losing oil pressure through the main bearings when they wear out? I didnt claim I did a complete overhaul on this engine anyway.
I am sure I am going to pull this engine out again, and I will definately do everything at that point.

I did read a few threads debating whether a shimmed factory wastegate would hold 15psi to redline In my case I find if I set the boost controller to anything more than 12~13psi, I will lose 3 psi by redline. If I want 15psi @ 6000rpm, I need to set the boost controller for 18~19psi peak. My leakdown is less than 2%, my wastegate is in good shape, and the turbo is fully functional. This eliminates any such factors some were debating.

Is the wastegate the issue? I dont think so in this case (I do admit the DP waste is superior). Maybe the compressor side of the turbo can't keep up with the motors appetite at higher rpms? Honestly though, has anyone held 15psi from 3000rpm to redline with a k26 variant by changing to a tial wastegate?

Waterguy

Both. Main bearing wear results in lower oil pressure, which can be worrying on a track day. Thrust bearing wear can allow the crank walk forward and back, and eventually get so bad that you get the pistons wearing against the side of the bores - not a pretty site.

I didn't mean to be critical. After all, I did rod bearings without doing main bearings. It's just that I have read so many times that the rod bearings are such a weak point in these engines, but the bottom end will last forever. The main bearings, especially the thrust bearings, do show wear at 100K miles. Having done rod bearings and an oil cooler re-seal with the engine in the car, and now also having helped pull a couple of engines, my recommendation would be to pull the engine and do the mains and rods at the same time. The engine goes in and out the bottom fairly easily, and it is so much easier and quicker to work on the engine when it is out of the car.

Well, some people have claimed to have seen it, but I didn't. The compressor side of my rebuilt K26-8 runs out of flow at high rpm. Not as bad as my old K26-6, but it definitely falls off starting around 5500 rpm. However, the turbo spools SO much quicker with the Tial, especially in dual port mode. That is where the benefit comes.