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Heads lifting under boost
Hello , im referring to a prev post, Mr Fairman made a good comment when noticed a small amount of oil near where I was installing air plugs and said that this can be from head lifting under boost...I didn't follow it up at the time but obviously it cant be a good thing..
Q: I don't want to stop boosting, so what do I do, do I retorque?? if so how much around 30? If so can someone send me a link on howto? cos im not sure which nuts I should tighten, (serious), If other questions cant be helped with pls I need a link or pic showing exactly the nuts that hold the head down so I can at least take photos of them and post here for opinion. OR do I drop the spring on WG to a softer one and do nothing with the nuts? Advice ![]() BTW: this is not a joke thread I do want to know how to do this thx
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Wheels Last row 1977 3.0 930 260hp built, still reassembling Row 1998 996 MK1 3.4 296hp new daily driver |
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,844
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I'd say, turn the boost up within safe CIS capabilities and forget about it.
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Registered User
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OK that's easy then
![]() Im also thinking/wondering that if heads do lift under boost then its sort of acting like a buffer against pistons blowing up because the pressure is relieved between the head and block??? But the problem is that when it happens acceleration is lost! once the pressure is reached it lets go and with it the power doesn't make it to the rear wheels So whats the solution? I don't want to add a gasket as that would most likely lower compression and in turn lessen power to the wheels.. Anyone got a link?
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Wheels Last row 1977 3.0 930 260hp built, still reassembling Row 1998 996 MK1 3.4 296hp new daily driver |
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Registered
Join Date: Jun 2007
Location: Kauai, Hawaii
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88' 930 03 Tacoma, 04 Duramax, 06 R350 Benz If you are traveling at the speed of light & turn on your headlights, does anything happen? |
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Good information,
I dont feel Porsche left that out on purpose though I think that it was just probably never thought of at the time, maybe they didn't do enough miles before release for the problem to arise. Because the expense would have been neligible in comparism to the sodium filled valves and nikasil pistons which were standard, Most likely an oversight id say But that solution is out of my resources unfortunately...one day ![]()
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Wheels Last row 1977 3.0 930 260hp built, still reassembling Row 1998 996 MK1 3.4 296hp new daily driver |
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,844
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No pressure is lost. The highest pressure is when the piston is near top dead center - well above cylinder and block mating surfaces.
I'm on the side that believes heads do not lift... ![]() |
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Crotchety Old Bastard
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I would think if the heads were lifting you would have stripped or broken head studs. No other way they can lift. The sound of broken head studs is unmistakable ...
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds '78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8 |
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Banned
Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,760
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Quote:
Regarding the oil seepage - there is nothing you can do about it without disassembling the top end, having the mating surfaces checked for flatness (and having them machined accordingly) and installing superior head studs. Does the amount of seepage mean you must do this now? Absolutely not - not nearly bad enough if none of the studs are currently broken. For the time being, simply stick to reasonable boost levels like Tippy said (best to stay at or below .8 BAR with the OEM intercooler). And PS - smooch it, bub!!! ![]() Last edited by Ronnie's.930; 07-23-2014 at 10:35 PM.. |
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newbie
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When i first bought my car i had a funny banginig noise when on boost only sounded like the wastegate banging. It tuned out to be lifting heads due to a broken head stud.
i still have an oil weep around the head but believe its from the rocker cover. Do you have a banging noise when on boost? Gas leaking from the lifting head or just the ehad chattering on to the barrel. Mine went on for about 6 months before i had the top end rebuild. Hopefully you only have a slight oil weep, Tim |
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Registered
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 2,764
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I've heard both high boost Turbos and high compression RSRs lift their heads, despite running 993T head studs. What does it sound like? Tap the fins of a cylinder head and they make a characteristic ringing sound. You can hear that over the roar of an RSR exhaust or an open wastegate.
But back to the OP and the idea of having oil leak out from between the head and cylinder -- if that were to happen, you have much bigger problems on your hands because there shouldn't be any oil in your combustion chambers.
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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 |
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R.I.P.
Join Date: Aug 2009
Location: Nicholson, Ga
Posts: 2,160
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Heads do lift. But it doesn't mean they need to be fastened tighter. Make sure you have no detonation, and the head studs are not broken. Then boost on my friend
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Registered
Join Date: Mar 2005
Location: Phoenix, AZ
Posts: 2,764
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Correct, definitely DO NOT fasten tighter. That's a sure way to warp cylinders and heads.
If you think the factory studs aren't holding, that they've weakened and/or stretched, then try loosening, lubricating and re-torquing (pray none snaps), or replace them.
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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 |
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,844
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Quote:
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Kartoffelkopf
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Quote:
S
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1993 (MY92) 964 Turbo 3.3 - Horizon Blue - Follow my 964 Turbo project here... http://forums.pelicanparts.com/911-engine-rebuilding-forum/626572-964-3-3-turbo-efi-conversion-using-syvecs-life-racing-engine-management.html On Instagram (along with other stuff) as @spenny_.b #spennybengineproject |
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Registered User
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Quote:
Today ill take a spring our and go back to .8 bar to be safe,
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Wheels Last row 1977 3.0 930 260hp built, still reassembling Row 1998 996 MK1 3.4 296hp new daily driver |
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Banned
Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,760
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Robus-maxxximus, that's definitely a good idea as it is really playing with fire to raise boost beyond stock settings without being able to verify/monitor safe air/fuel ratios . . . can run out of fuel and have detonation problems in a hurry by increasing boost pressure and not increasing fueling via an adjustable WUR.
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Crotchety Old Bastard
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Proper AFR's are just the baseline at that point. If the octane of the fuel isn't high enough bad things will happen fast. Engines need special build parameters to support high boost levels and high octane fuel which can burn hotter than gasoline depending on the mix. Typical OEM head studs and hardware are not used. I have seen pictures of heads welded on race engines, now THAT is hard core!
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds '78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8 |
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Registered User
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Quote:
I think the low compression of 6:5 to one plays a part in reliability, Even with all my later 930 bits ive added im going to go the smaller .8 spring doesn't worry me really as even when driving her around town she is torquey enough before boost anyway. Im just peeeed off at myself for installing the air plugs , should have left it alone all it did was give me unnecessary work in fixing leaks. anyway back to my New Paintjob, I call it Marrow Blue (my own invention) It goes on really nice and shiny ,but time consuming ill have to buy some wider brushes ![]() ![]() ![]() ![]()
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Wheels Last row 1977 3.0 930 260hp built, still reassembling Row 1998 996 MK1 3.4 296hp new daily driver |
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Chain fence eating turbo
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,844
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You are paintbrushing your car??
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Banned
Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,760
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I'm confident that is some Robby humor right thar! Regardless, the bulk of the paint is undoubtedly going straight up his nose!!!
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