1FastRedSC

It's been quite awhile since i updated the status of the 944 turbo since i blew it. I'll keep the details short....... 104mm je pistons 9 to 1 compression, the sleeves i think are darton's. I left the coolant drain on the block half open, gave it a hard run to dial in the correct fuel mixtures under boost for the tec 2, engine over heated spewing coolant everywhere and the motor died. After the carnage, engine was showing leak down numbers between 40-50% on all 4 with the air hissing out of the oil fill tube (blowing by pistons into the block).
Now, had free time last week (and got over the depression of blowing it up in the first place), took everything out, put the motor on the stand and started tearing it down expecting the worst. The oil i drained earlier looked bad as is (sludgy build up of metal shavings on the magnetic plug). So everything was actually going relatively ok until i got to pulling off the head......... Visable scoring on the walls going vertically (motion of the piston) and i can also feel them with my finger when rubbing the walls (relatively deep), on all four walls. That's where i stopped for now, piston rings are probably broken but i haven't yanked the pistons out yet.
What would be the best choice in this scenario?
1.Widen the bore a little more to 104.5mm (if possible) and get a different set of custom je pistons to fit.
2.Change out the liners for new ones (or different ones if possible) and salvage my pistons assuming they are ok (which i'm not sure off yet).
3.A suggestion of your own which i have not thought of yet........

SeaCay

Have someone else do the work for you???

Barry Johnson

First of all, that sucks and I feel your pain... My 928 cracked a cylinder right after I just put it back together after sitting for a year...

So, I'm not sure how thick the cylinders are, and if just going .5mm would be enough to smooth out the scoring on all cylinders. Pop out the pistons and have a look, my guess is that you might find some chipping by the rings. PLAN on replacing the sleeves and pistons. If you get lucky and the sleeves are salvageable, then you're 'under budget'. I wouldn't really use those pistons to be honest though, broken rings aren't too nice on pistons...

Also, what boost are you running on 9:1? How much did those sleeves run you?

amschnellsten

If you build it yourself the only person you can get pissed at is yourself. Personally I like modded cars that people built themselves and did not just throw money out for an artificial ego. If you can do it my hat is off to you.

RolexNJ

I hear and totally respect someone who can build a complete car by themselves, like Ski. Bret can rip apart a 951, and put it back together better than it ever was. And my hat goes off to him, plus, he's a great guy too! But I find your statement to be very interesting, and clearly tells me about your outlook toward people who are successful professionals. So for those that are very successful in their careers, and can afford to have a professional builder put together a top notch car for them have an artificial ego? I've never that one before, but, I'll keep that in mind as I build my car.

Have a pleasant evening too.

dand86951

If they are Darton sleeves then you can definitely bore them out to 104.5 or even 105 or 106. The pistons can be had from EBS Racing for around $700.00 a set and you can get a larger dish that should give a compression ratio in the range of 8.3. The good part about sleeves is that they can be bored out by any reputable automotive machine shop assuming they were installed correctly to begin with.

Dave951

Rolex, don't get bent out of shape bud. I think our fellow lister here is just trying to say that he prefers (and respects to the highest degree) a man who undertakes and completes the challenge of building up his own car. And similarly is just less enthused (personally) when a person takes a less active role in accomplishing the same goal.

[Granted his analysis (amschnellsten) and conclusion completely negates any consideration for the different amounts of free-time various individuals have to devote to their respective hobbies. But I am merely trying to explain what a fellow member is probably trying to convey (Not to mention try to prevent one less flame war)]

Disclaimer: By no means by writing this response do I claim agreement with the ideology presented by the party in question.

RolexNJ

I hear ya pal, I just don't appreciate a blanket statement. And I did "preface" my opening response saying I fully appreciate people who can do it themselves too. But one should think before making such uncalled for "ego" posts. I can make analogies about people developing their driving skills just the same. The ones who can and cannot afford the best race schools in the world. Yet I would never say that because I would come across as a pompous jerk. Sorry Dave that doesn't fly with me, that statement wasn't right.

1FastRedSC: Do a search on rebuilding. And if you need "expert" advice, I would look for posts by men named Ski, Tom G, Chris White, just to name a few, good luck and I'm sorry to hear about that.

Matt Sheppard

Some of you may remember the Cooper cup? The award for the years worst DIY blunder. One had to draw blood or be hospitalized during their episode to be in the running. This example, though painfully expensive is a small oversight - I've heard of far worse on these boards. Give the guy a break.

1fastredsc: I admire your pluck staying after it like this. It's true: the little foxes spoil the vine!

I blew up the first bug motor I ever built because I didnt torque the air-cleaner screw on tight enough the night I finished it (post 2 am). The air cleaner element got loose, sucked in the doghouse fan and the motor overheated. Blew oil all over the 57 fwy - quite spectacular really. Best time to blow an engine is when it's behind you.

I'd bore to 104.5 and get new jugs. I have a TEC 2 system I've yet to install. I'd love to talk to you about your tuning approach, timing, VE tables if you are up for that.

David Floyd

+1

SeaCay

A somewhat different approach to your response than Rolex...

My comment, although somewhat lighthearted (as evidenced by the little hiding emoticon), also points out that the unfortunate builder perhaps is in over his head on this project. If not, I wholeheartedly apologize to Mr.1FastRedSC for my presumptions. If so, however, perhaps he would best be served by allowing a professional to do the critical componentry and tuning, rather than throwing good money after bad. It's all fine and dandy to bolt up a few parts and let 'er rip, it's another thing altogether to get a TECII system up and running from scratch without going through major $$$ and heartache.

To the OP. What caused the engine to die to begin with, and have you made a plan to resolve that issue prior to starting a new engine? Answer these important questions before you ever make the decision on what bore or pistons/liners to use.

RolexNJ

Very valid and well said points, kudos my friend.

Dave951

Speaking of which is the Rolex school of racing open for business yet? I wanna be in the first graduating class.

RolexNJ

Nope, it's closed. Only open to Ferrari members now? --->

1FastRedSC

Everyone makes a mistake and learns, and it seems that genetics favor the hard mistakes in my case. This motor started out getting (what i think are darton sleeves) machined from p&w machine in whippany, new jersey about 5 years ago. It's my fathers, but since i'm the ME student of the family, i have a helping hand (most of the time the only hand) in building it. 104mm je pistons that are supposedly 8.5:1, ceramic coated domes, teflon coated skirts, pauter rods, lightened and knife edged crank, (someone i cannot mention on these forums) port job stage 3 with flame rings machined into the head. Then on the outside is the piping, intake, turbo and tec2 from SFR. Everything was slapped together but the car didn't run first go because the injector driving circuit inside the tec 2 was blow'n. After electromotive fixed it, life beckoned and we all moved to new mexico (that's another story in itself). Almost a year later we finally get around to messing with the car again, this time it fires up. After some driving and tuning, turbo blows (k26-6) and head gasket pops spewing water everywhere (including in the chamber).
Then it becomes time to try different head gaskets to see which will work. Lesson 1, never assume that heads that were machined by someone from a reputible shop are done correctly, MEASURE EVERYTHING, because the flame ring machined into the head was machined for a 100mm bore, not 104 even though that was clearly stated before the build got started. Next performance developments gets there hands on the block and head (who i highly recommend) and ditch the flame ring, press in filler rings to keep the head flat (for use with a cometica gasket) and inspect the block. Lesson number 2, don't assume that the compression ratio that JE tells you is correct, because after measuring the dome volume, piston cup, and numbers that PD had measured, turned out we had 9:1 compression. Lesson 3, numbers can be decieving, because that port and head job that was done by (shop i cannot mention on this forum), turns out it flows 2 cfm better than stock, instead of the 30cfm they claim, not to mention that the valve work itself needed to be redone totally (everything documented by PD). I get it all back sparkling clean wrapped in plastic bags to keep the moisture of oil on the surface of the liners (PD sends them that way). At this point i'm on my own since my dad gave up on the car long ago. I put it all back together, but appearantly got a little excited and didn't tighten everything (block drain) took it out for a run to try and finish my tuning (almost had perfect fuel mixture) and boom, smoke everywhere, car won't start, water shooting out the bottom. Lesson number 4, while water at normal temperature and atmospheric pressure will not push past a half threaded block drain (No leaks when cold), at 1 bar over atmosphere and 190 deg F it will push it's way right past it without much hesitation.
On another car (my car)......
Lesson 5, don't assume that the areas you can't see during a topend rebuild are fine and clean because the motor was operating fine previously. Turned out one of the chain guides fell apart and was inside the case. 1400 miles after a flawless top end rebuild (less than 5% leak on all 6 cylinders stone cold), the oil spray bar in the cam towers got clogged with plastics bits from ...... you guessed it ....... the broken chain guide that i never found.
So as you can see, i don't make the same mistake twice, just EVERY single mistake once. And i'm too proud and stubborn to ever let someone else work on our cars. So gentlemen, back to the discussion if you will...................