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Registered User
Join Date: Jul 2015
Posts: 19
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CMW Head issue - Valve seat not sealing
Hi All, just thought I'd reach out and ask for peoples thoughts on an issue I'm having with my engine.
Exhaust valve seats are no longer sealing after only 50hrs operating time on the a new engine. It seems a portion of the valve seat appears to have worn away, but only about a third of it, the rest appears fine. The valve looks ok, just the valve seat has suffered. I've been logging and monitoring both cylinder heads temps as well as air fuel ratios and the engine has been running very well. The heads were purchased in 2013 and did have many machining issues, but I spent another $3K with a local racing machinist to get everything sorted. All 6 exhaust valves suffer from this same issue. Engine is running in turbo form Have uploaded a picture, not very clear, but if it uploads correctly you can see a section that shows the valve seat angle worn away (the section furthest away from the spark plugs) Keen for everyone's thoughts Cheers Robert 
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07-16-2015, 06:30 AM
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Registered User
Join Date: Jul 2015
Posts: 19
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 Trying to show the issue a bit better, the red arrows show the section the seat has lost it's sealing surface, looks and feels rounded |
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07-16-2015, 06:35 AM
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Registered
Join Date: Mar 2006
Location: MD/DC/VA
Posts: 5,872
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I would think that the issue is the seat being worn, that being the case, new ones will need to be properly fitted and ground.
Not knowing the particular issues you had prior with machining, but this is something that should have been addressed then. Maybe you should look into using someone more familiar with these heads like Cusimono (SP) himself, or Xtreme Heads as opposed to the "local racing machinist."
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RGruppe #180 So many cars.. so little time!! Last edited by onboost; 07-16-2015 at 07:48 AM.. |
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07-16-2015, 07:29 AM
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Registered
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Send them to bill at Xtreme.problem solved. Oh yeah,pull out the wallet and be prepared to wait
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88 930 3.4 ,Twin plugged billet Xtreme cylinder heads and denso COPs, Dougherty custom GT 2 evo cams,pauter rods,Garrett Gt40,ms3x Efi ,1100cc injectors,extrude honed 3.2 intake,TK billet fullbay I/C,MODE headers,KEP stage 2, E-85, 706 rwhp |
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07-16-2015, 07:39 AM
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Banned
Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,559
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That quick wear pattern would indicate to me that the valve was not oriented correctly to the valve seat - maybe a problem with the installation of the valve guides (set cockeyed in their bores or not reamed/honed straight and true), the seats (if they were new), or the ground angle of the seats was done slightly differently to the corresponding angle on the valve faces.
Last edited by Ronnie's.930; 07-16-2015 at 10:54 AM.. |
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07-16-2015, 10:52 AM
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Forced Induction Junkie
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Have you verified the valves are not bent? Spun them in a drill chuck, for instance? Valves haven't kissed the pistons?
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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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07-16-2015, 02:26 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,131
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Sounds like the valve seats weren't lapped after replacement
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07-16-2015, 02:31 PM
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Registered User
Join Date: Oct 2010
Location: Southern NH
Posts: 3,553
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have you tried lapping with some compound to see how bad they are?
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07-16-2015, 02:36 PM
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Metal Guru
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Valve guides and seats are machined together to prevent just this.
As other mentioned, a bent valve or out of spec guide would cause a similar problem. If it were my car, I'd have every head reconditioned and be done with it.
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Paul B. '91 964 3.3 Turbo Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb |
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07-16-2015, 03:27 PM
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Registered
Join Date: Jun 2008
Location: Yamhill OR.
Posts: 455
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Check to make sure the valve are straight. Any over revs?
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07-16-2015, 04:19 PM
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Registered
Join Date: Jul 2006
Location: S. Florida
Posts: 7,249
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The best place on the planet to fix your cylinder heads is: Xtreme Cylinder Heads And Castings
Bill is a cool dude too. Xtreme Cylinder Heads, Inc. Xtreme Castings Corporation 772.286.1660 772.286.1217 fax 3471B SW Palm City School Ave. Palm City, FL 34990 bill@xtremecylinderheads.com Good luck with it. |
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07-16-2015, 05:28 PM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,131
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Quote:
They are so special. Porsche heads work differently than any other head/valve/seat/seal/guide make in the world, so you better take them to Xtreme only! Sarcasm off.  Seriously, any competent machine shop can identify if the guides are shot, or the valve seat was never lapped after guide replacement. |
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07-16-2015, 06:24 PM
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Registered User
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that much carbon in 50 hours? bent valve, worn guides
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07-17-2015, 03:17 AM
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Registered
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Valve guides were shot and should have been replaced is my internet guess by looking at pictures.
The worn radius on the edge of the guide in your picture and the wear you describe is the bases of my guess. I bet your valve guides were not replaced. |
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07-17-2015, 04:57 AM
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 9,131
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Give them to "cgarr", a Pelicanite. He has insanely quick turn around and charges peanuts.
I'm dead serious. |
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07-17-2015, 11:52 AM
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Forced Induction Junkie
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Talk to Chris at TurboKraft. He's worked on CWM Heads and has some horror stories to share.
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07-17-2015, 01:32 PM
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Registered
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If you put the valve in the guide and wobble it, can you get enough movement to match the marks? Then try rotating the valve and see if it goes in/out of seat alignment. That should give you a clue.
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-) |
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07-17-2015, 02:30 PM
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Turbo Hooligan
Join Date: Sep 2007
Location: The Old World
Posts: 1,234
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Most turbo race heads are junk after 50hrs. comes with the territory.
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07-17-2015, 02:41 PM
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Banned
Join Date: Jun 2015
Location: Down South, USA.
Posts: 287
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You are so right!!BTDT!!
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07-17-2015, 04:22 PM
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Registered
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 2,855
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One more endorsement for mi amigo Bill DiCondina:
2010: An EFI Hot Rod Odyssey Read posts #25 - 72, results in post #72. Before Bill at Xtreme worked on those heads, I'd have valued them at $16/ton. Several weeks and many dollars later, they were something worth having on a 911 Turbo. Worth every penny spent. They helped turn that stroker 3.5L into a fire-breathing monster you could easily drive daily for your commute through stop-and-go traffic.
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Chris Carroll TurboKraft, Inc. Tel. 480.969.0911 email: info@turbokraft.com http://www.facebook.com/TurboKraft - http://www.instagram.com/TurboKraft Last edited by TurboKraft; 07-21-2015 at 03:55 PM.. Reason: typo |
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07-21-2015, 03:54 PM
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friendly
1985 Porsche 930 Fac. Slantnose 3.3l
1991 Porsche 964 Turbo
