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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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930 rebuild in progress.......I need your help and opinions on the mess inside
Engine has 34 hours since complete build. Power was down, so we did a leakdown: 40% on number 3.
So the engine goes into the shop for a look-see. Gets worse the further we look - first is the burnt valve, no big deal. Then the shuffled heads and the gouges on the cylinder tops. Uh-oh. Then the scoring on the cylinder walls. Can these cylinders be saved? They were brand new 34 track hours ago.     
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 09:33 AM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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Cylinder and heads:
  
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 09:35 AM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 09:36 AM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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#3 and #5 had broken top rings, yet scoring is on nearly all the cylinders
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 09:38 AM
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Registered
Join Date: Mar 2001
Location: Marysville Wa.
Posts: 22,435
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heads can be flycut and cylinder tops can be cleaned up in a lathe, but the scoring suggests a new set of P+Cs is in order. and limit your boost in the future. it's been blowing past at least one head for a while too. no broken studs? maybe everything is not on the same plane. maybe swap the all-threads for something better.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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05-28-2006, 10:52 AM
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Registered
Join Date: Mar 2001
Location: Marysville Wa.
Posts: 22,435
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you might want to go a bit deeper and check the rod bearings too, considering the detonation issue that broke the rings.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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05-28-2006, 11:39 AM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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No broken studs. Has fully threaded studs that are non-magnetic (dilivar?). ARP will replace the threaded units. 'Fire ring' (slots cut in heads and cylinders) will help to locate the heads to the cylinders and help prevent blow by -
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 11:47 AM
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Me like track days
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Location: Kirkland, WA
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The boost has been a stock .8 bar since the initial build.
If the pistons were installed 'backwards', would it cause this scoring?
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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05-28-2006, 11:58 AM
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Forced Induction Junkie
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Those pistons look like they are higher compression than the stock ones. What compression ratio were you running?
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Dave '85 930 Factory Special Wishes Flachbau Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P |
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05-28-2006, 12:06 PM
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Registered
Join Date: Aug 2004
Location: Sunny San Diego
Posts: 210
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Curious...did the pistions get fouled after the rebuild? Were all the carbon buildup cleaned before assembly? Nothing to do with the post, but just wondering if it can get that dirty only after 34 hours?
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David Nguyen 1987 930: 2700 lbs, 408 RWHP/405 RWTQ 930 pics: http://alturl.com/899f9 930 Engine rebuild pics: http://alturl.com/25qcy |
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05-31-2006, 06:41 AM
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Registered
Join Date: Oct 2001
Location: Momence, IL 60954
Posts: 1,911
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I would pull all the studs out and measure them- they all should be the same length, if not, they should be replaced. I also suggest against an all thread stud here- too rigid. As far as the cylinder faces, I would have them surface ground rather than decked in a lathe, but I would replate the cylinders and have them cryogenically treated if you plan on re-using them before having that done. I'd be willing to say that you've toasted them and you'll never get any kind of longevity out of them. Flame ringing also wouldn't be a horrible idea the second time around.
As far as the pistons being installed backwards, I don't think you can- the JE's don't have offset pins. The scuffing could have come from the piston heating up real fast and out expanding the cylinder. Coated skirts help that to some extent, but the coating is sacrificial so it won't last forever.
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Charles Navarro President, LN Engineering and Bilt Racing Service http://www.LNengineering.com Home of Nickies, IMS Retrofit, and IMS Solution |
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05-31-2006, 07:07 AM
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Super Moderator
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Almost looks like that one valve has a pre-burn slot in it? I'm wondering (especially with the broken rings) if you weren't detonating...
Are you sure you were running .8 bar boost? How about fuel? Was it quality? Ask Steve at Rennsport what he things about most fuels these days...
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Chris ---------------------------------------------- 1996 993 RS Replica 2023 KTM 890 Adventure R 1971 Norton 750 Commando Alcon Brake Kits |
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05-31-2006, 12:13 PM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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Bottom end.
-------- #6 cylinder - Caps  Bearing shell  Other side of shells. THE ugliest thing you want to see on a 30 hour engine.  Will be 'interesting' to see what the other bearings look like.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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06-09-2006, 02:35 PM
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Forced Induction Junkie
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Craig,
You did a teardown a right right time. Anymore on that engine would have been catastrophic. The crank mains and journals will tell a lot too.
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Dave '85 930 Factory Special Wishes Flachbau Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P |
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06-09-2006, 02:45 PM
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Registered
Join Date: Aug 2004
Location: Sunny San Diego
Posts: 210
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Other than the lost of power, what else did you notice that led you to believe that there was something seriously wrong with the rebuild? (i.e., strange noises?)
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David Nguyen 1987 930: 2700 lbs, 408 RWHP/405 RWTQ 930 pics: http://alturl.com/899f9 930 Engine rebuild pics: http://alturl.com/25qcy |
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06-09-2006, 02:46 PM
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Me like track days
Join Date: Sep 2003
Location: Kirkland, WA
Posts: 10,209
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Noticed a loss of power late last year
Checked timing and mixture - both were fine. Did a dyno run in December - down 56 hp. Checked leakdown - 40% on #3 through the exhaust.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ - "930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe Movie: 930 on the dyno |
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06-09-2006, 03:29 PM
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Registered
Join Date: Apr 2000
Location: Kansas City
Posts: 1,675
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It will be interesting to see what the root cause is here... that thing looks like it has been through a war!!
All the best, Craig, JA
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John - '70/73 RS Spec Coupe (Sold) - '04 GT3 |
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06-09-2006, 07:43 PM
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Super Moderator
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Those are some ugly bearings , glad you caught it!
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Chris ---------------------------------------------- 1996 993 RS Replica 2023 KTM 890 Adventure R 1971 Norton 750 Commando Alcon Brake Kits |
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06-10-2006, 06:29 AM
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Registered
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Ughh - I had a failure on a "pro" built engine years ago because the crank was not cleaned property. I should say spectacular failure since the rod went thru the case and it was in a race...
Have you noticed higher than usual oil temps?
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Chris https://dergarage.com ‘07 GT3, '80 SC Weissach (For SALE), '01 986S, '11 958S, '18 Stelvio, '18 Dursoduro 900 |
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06-10-2006, 08:41 PM
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resident samsquamch
Join Date: Oct 2005
Location: Cooterville, Cackalacky
Posts: 6,815
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I'm confused as to how this engine has 34 hours on a "complete rebuild". Those bearings look so ugly. I guess this is your track car? I don't race, but I wonder what 34 hours of race time traslates into street years...sort of the 7 dog year conversion. It looks worse than my engine that had never been a part in close to 20 years. I guess when things start to go bad in a turbo engine...they go bad real quick like!
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-jeff back in the saddle: '95 993 - just another black C2 *SOLD*: '87 930 GP White - heroin would have been a cheaper addiction... "Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP  )
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06-11-2006, 03:31 AM
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1985 Porsche 930 Fac. Slantnose 3.3l
1970 Porsche 911 S 
911 3.8 "RS"
993 Cab
