Blown Head Gasket -
05-03-2002, 06:53 PM
#1
Three Wheelin'
Thread Starter
Join Date: Jun 2001
Location: SF Bay Area
Posts: 1,276
Likes: 0
Received 0 Likes
on
0 Posts
Blown Head Gasket -
Well I noticed a little oil leaking from my 86 911 Turbo for the first time the other day. The car has 51,000 miles and has never dripped oil so I was a bit concerned. Took it to the tech today and it has a blown head gasket. They think a broken head bolt is the likely cause, so the engine needs to come out. Crap, crap, crap! We intend to install Raceware head bolts while in there and flow and polish the heads. The car has most of the usual mods, K-27, Kokeln IC, GHL Headers, SC Cams, Mille Miglia muffler, 1 bar boost, etc. I do not need more HP but would like to be sure the engine is as well protected as can be. Any suggestions while the engine is out? Should I cut down the boost? My mechanic does not think the 1 bar boost caused the problem, but we have talked about going to an adjustable boost system so I can tone it down when not needed.
05-03-2002, 09:06 PM
#2
Addict
Rennlist Member
Rennlist Member
Groan...sorry to hear that ZCAT.
Your list looks good, but it also might be a good time to do valve guides and upgrade the rod bolts.
Then there are those little cosmetic things like painting/polishing the fan, valve covers and cleanup of the top and bottom.
I sort of prefer the electronic boost controllers Apexi or HKS. Lots of flexibility and better performance.
I like what Pete Carroll has done to his engine - with the exception of the turbo, very understated beauty.
Your list looks good, but it also might be a good time to do valve guides and upgrade the rod bolts.
Then there are those little cosmetic things like painting/polishing the fan, valve covers and cleanup of the top and bottom.
I sort of prefer the electronic boost controllers Apexi or HKS. Lots of flexibility and better performance.
I like what Pete Carroll has done to his engine - with the exception of the turbo, very understated beauty.
05-04-2002, 01:12 AM
#3
Nordschleife Master
[quote]Originally posted by ZCAT3:
<strong>Should I cut down the boost? </strong><hr></blockquote>
Head gaskets blow as a result of a poor A/F ratio. You could safely run 20lbs all day if you kept it close to 12.5:1 . I would dyno the car and get a good A/F reading to see what is going on? <img src="confused.gif" border="0">
<strong>Should I cut down the boost? </strong><hr></blockquote>
Head gaskets blow as a result of a poor A/F ratio. You could safely run 20lbs all day if you kept it close to 12.5:1 . I would dyno the car and get a good A/F reading to see what is going on? <img src="confused.gif" border="0">
05-06-2002, 01:39 PM
#7
Three Wheelin'
Thread Starter
Join Date: Jun 2001
Location: SF Bay Area
Posts: 1,276
Likes: 0
Received 0 Likes
on
0 Posts
Hi T.P. - I am just learning the various engine parts. The gasket I am referring to can be seen poking out a bit when looking up under the car. It sits under the cylinder. It is a brass colored very thin metal gasket.
As an aside, the car is a Euro car which I though meant a bigger fuel delivery system. I only have 6K on the car since modifying it and nothing we are doing it extreme. Even Bruce Anderson says 1 bar boost should be fine. This is bumming me out - the car is beautiful but the price is getting steep.
As an aside, the car is a Euro car which I though meant a bigger fuel delivery system. I only have 6K on the car since modifying it and nothing we are doing it extreme. Even Bruce Anderson says 1 bar boost should be fine. This is bumming me out - the car is beautiful but the price is getting steep.
Trending Topics
05-06-2002, 04:05 PM
#8
The gasket you are referring to is indeed between the cylinder and crankcase. I know this will probably get a lot of negative responses, but perhaps you should ask your mechanic to 1st remove your valve covers and inspect your head studs. If they are intact, then have him drain out the oil, clean the area where the leak is occuring, and thereafter apply a high-temp sealant (black color). This will most likely stop the leak. I don't think you have to worry about decreased compression, because the gasket you are describing is below the piston ring.
05-06-2002, 04:17 PM
#9
Three Wheelin'
Thread Starter
Join Date: Jun 2001
Location: SF Bay Area
Posts: 1,276
Likes: 0
Received 0 Likes
on
0 Posts
T.P. - can they remove the bottom of the engine (valve covers) without removing the engine form the car? They are going to do a compression test before anything else, to see if we can sniff out any other problems. If there appears to be serious issues, I may send the car up to Steve Weiner in Portland for a 3.4 twin plug conversion.
05-06-2002, 05:24 PM
#10
The valve covers can be removed without dropping the engine. If compression is good and the head-studs are intact, it would be a shame to have to rebuild the engine to stop a lousy leak - it sounds like you've spent a lot already. If the leak's not too severe, brushing a little hi-temp sealant over the leak will stop it. If you're not selling the car who will care?
05-07-2002, 01:44 PM
#12
Nordschleife Master
Luke,
For longevity reasons, it is not good to run an air cooled Porsche engine past 1bar boost. Porsche seemed to limit its race cars to 1.6/1.7 bar boost but that was with special headgaskets and sealing surfaces.
For longevity reasons, it is not good to run an air cooled Porsche engine past 1bar boost. Porsche seemed to limit its race cars to 1.6/1.7 bar boost but that was with special headgaskets and sealing surfaces.
05-07-2002, 05:42 PM
#13
Three Wheelin'
Thread Starter
Join Date: Jun 2001
Location: SF Bay Area
Posts: 1,276
Likes: 0
Received 0 Likes
on
0 Posts
O.K. - I had a leakdown and compression test done with the following results:
1: 140 / 10%
2: 140 / 8%
3: 145 / 10%
4: 140 / 8%
5: 140 / 8%
6: 140 / 8%
These numbers look pretty good - my mechanic figures that the engine is healthy and the gasket just needs to be repaired - which is going to cost upwards of $5,000. He was not too keen on the sealant proposal.
1: 140 / 10%
2: 140 / 8%
3: 145 / 10%
4: 140 / 8%
5: 140 / 8%
6: 140 / 8%
These numbers look pretty good - my mechanic figures that the engine is healthy and the gasket just needs to be repaired - which is going to cost upwards of $5,000. He was not too keen on the sealant proposal.
05-07-2002, 06:29 PM
#14
Intermediate
Join Date: Aug 2001
Location: Potomac Fall, VA
Posts: 46
Likes: 0
Received 0 Likes
on
0 Posts
Bill
just to chime in a little late as I am rebuilding my engine due to bad upper head stud. I don't want to rain on the diagnosis. There may be a bad exhaust side stud that is causing the gasket to be loose. It would pay to check torque on all before you begin the work. I don't see how that copper gasket could fail. I checked my compression beforehand and had better results than you. I was at less than 5% on all cylinders. I'd be happy to share my rebuild experience with you. Good luck and we'll hope for the best.
just to chime in a little late as I am rebuilding my engine due to bad upper head stud. I don't want to rain on the diagnosis. There may be a bad exhaust side stud that is causing the gasket to be loose. It would pay to check torque on all before you begin the work. I don't see how that copper gasket could fail. I checked my compression beforehand and had better results than you. I was at less than 5% on all cylinders. I'd be happy to share my rebuild experience with you. Good luck and we'll hope for the best.
05-07-2002, 06:44 PM
#15
Three Wheelin'
Thread Starter
Join Date: Jun 2001
Location: SF Bay Area
Posts: 1,276
Likes: 0
Received 0 Likes
on
0 Posts
Hi John - thanks for the input. No matter what we end up doing, will be opening the engine to check all cylinders so if there is a broken stud we will see it. My debate now is whether to go the extra mile so to speak and upgrade the engine while we are at it.