Head Job Went Horribly Wrong
09-19-2014, 12:25 AM
#31
Rennlist Member
You guys have me worried now ... lol I just finished reinstalling everything after replacing broken rings on three cylinders and i haven't attempted to start the car yet,going to pressure test the cooling system tonight to see if there's any water leaks and fire it up tomorrow ! I torqued everything according to the Porsche workshop manual ... Cheers Phil
09-19-2014, 12:49 AM
#32
Rennlist Member
I still like a light coat of copper spray on head gaskets. I know the manufacture states not needed, do not use, etc. Has always worked for me.
Also the bleeding procedure alone on these cars is enough to destroy a head gasket if not done properly. A few tricks.
1) Open the bleed hole in the thermostat with a little larger drill and install so the hole is at the highest point.
2) Install the Lindsay Racing steam vent kit (or equivalent). After years of dreading any time I had to bleed to cooling system, this modification alone is worth the money just in bleeding procedure ease of mind and time saved alone.
3) After the first torque sequence I let the car sit for a while as I cleaned up the cam tower, etc. Then I went back and retorqued to the same value (every bolt took some addl torque). Then I did the 90 + 90.
Also the bleeding procedure alone on these cars is enough to destroy a head gasket if not done properly. A few tricks.
1) Open the bleed hole in the thermostat with a little larger drill and install so the hole is at the highest point.
2) Install the Lindsay Racing steam vent kit (or equivalent). After years of dreading any time I had to bleed to cooling system, this modification alone is worth the money just in bleeding procedure ease of mind and time saved alone.
3) After the first torque sequence I let the car sit for a while as I cleaned up the cam tower, etc. Then I went back and retorqued to the same value (every bolt took some addl torque). Then I did the 90 + 90.
09-19-2014, 06:48 AM
#33
Rennlist Member
Thread Starter
There seems to be two schools of thought on the torque method. I have read that Porsche recommends for the 1986 944, to torque the head to 15 ft/lbs then to 37 ft/lbs, and then the final torque of 66 ft/lbs. I also called a local Porsche dealer and they stated they use those torque values.
Then I have also read and have been told that the 90 degree torque angle method is the way to go. When I took the head off the car originally, the nuts were extremely tight. They were probably torqued to the 90 degree angle method. I think I will be going back to that method.
Before I removed the head after the gasket blew, I loosened the head nuts and then torqued them in sequence to 15 ft/lbs and then to the first 90 degree angle. I then torqued the first nut to the second 90 degree angle and then checked it with my torque wrench. It checked out at 107 ft/lbs. It seems pretty high of a torque setting, however after talking with Van, he assured me that that torque value probably wasn't too high. Which makes sense due to how tight they were originally, as they were difficult to loosen.
Machine shop checked the head out yesterday morning and they said it was fine. Held vacuum on all intake and exhaust ports. They shop said the plane was fine and the guy was confident that it would be fine to reinstall.
Then I have also read and have been told that the 90 degree torque angle method is the way to go. When I took the head off the car originally, the nuts were extremely tight. They were probably torqued to the 90 degree angle method. I think I will be going back to that method.
Before I removed the head after the gasket blew, I loosened the head nuts and then torqued them in sequence to 15 ft/lbs and then to the first 90 degree angle. I then torqued the first nut to the second 90 degree angle and then checked it with my torque wrench. It checked out at 107 ft/lbs. It seems pretty high of a torque setting, however after talking with Van, he assured me that that torque value probably wasn't too high. Which makes sense due to how tight they were originally, as they were difficult to loosen.
Machine shop checked the head out yesterday morning and they said it was fine. Held vacuum on all intake and exhaust ports. They shop said the plane was fine and the guy was confident that it would be fine to reinstall.
09-19-2014, 09:00 AM
#34
Drifting
Final outcome was 28% leakdown on cyl 2 and 4 and i had to tie rap the oil dipstick for the enduro as it had an urge to blow out through the hood due to the crankcase pressure ...
My dyno guy told me the car was starving for fuel with the stock 2.5 bar fuel regulator, it's all good now as i installed my Lindsey rail with an adjustable fuel pressure regulator !
Going to set the rings and tune the fuel mixture on the dyno Monday morning
We have our last race of the season at Circuit Mont Tremblant next weekend.
Cheers
Phil
09-19-2014, 11:13 AM
#35
Just a car guy
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Sorry to hear of your problems. Looks like you will have it sorted out soon.
Minor setback compared to some of my past experiences. One in particular still stings - after more than 8 years...
I missed the final torque on a connecting rod end. Imagine the sinking feeling when it let go after about 2 seconds of running. The sound of a piece of block hitting the pavement was like an explosion compared to the silence of the engine stopping!
That was a rather expensive mistake. Needless to say, I have become very careful about checking and double checking torque and proper installation since that time.
A paint marker is a handy tool.
Good luck with the rebuild.
Minor setback compared to some of my past experiences. One in particular still stings - after more than 8 years...
I missed the final torque on a connecting rod end. Imagine the sinking feeling when it let go after about 2 seconds of running. The sound of a piece of block hitting the pavement was like an explosion compared to the silence of the engine stopping!
That was a rather expensive mistake. Needless to say, I have become very careful about checking and double checking torque and proper installation since that time.
A paint marker is a handy tool.
Good luck with the rebuild.
09-19-2014, 12:19 PM
#36
Three Wheelin'
Nice to hear it was a relatively simple cause. The damage makes sense based on your description of how it ran nice when first started up and then deteriorated rapidly. At least the piston has now been steam cleaned!
It is my understanding that the torque method was updated for all models. The 90 degree turn method is more accurate, but you hardly ever hear about the NA's blowing head gaskets. It is always the turbos.
It is my understanding that the torque method was updated for all models. The 90 degree turn method is more accurate, but you hardly ever hear about the NA's blowing head gaskets. It is always the turbos.
09-19-2014, 12:57 PM
#37
There seems to be two schools of thought on the torque method. I have read that Porsche recommends for the 1986 944, to torque the head to 15 ft/lbs then to 37 ft/lbs, and then the final torque of 66 ft/lbs. I also called a local Porsche dealer and they stated they use those torque values.
Then I have also read and have been told that the 90 degree torque angle method is the way to go. When I took the head off the car originally, the nuts were extremely tight. They were probably torqued to the 90 degree angle method. I think I will be going back to that method.
Before I removed the head after the gasket blew, I loosened the head nuts and then torqued them in sequence to 15 ft/lbs and then to the first 90 degree angle. I then torqued the first nut to the second 90 degree angle and then checked it with my torque wrench. It checked out at 107 ft/lbs. It seems pretty high of a torque setting, however after talking with Van, he assured me that that torque value probably wasn't too high. Which makes sense due to how tight they were originally, as they were difficult to loosen.
Machine shop checked the head out yesterday morning and they said it was fine. Held vacuum on all intake and exhaust ports. They shop said the plane was fine and the guy was confident that it would be fine to reinstall.
Then I have also read and have been told that the 90 degree torque angle method is the way to go. When I took the head off the car originally, the nuts were extremely tight. They were probably torqued to the 90 degree angle method. I think I will be going back to that method.
Before I removed the head after the gasket blew, I loosened the head nuts and then torqued them in sequence to 15 ft/lbs and then to the first 90 degree angle. I then torqued the first nut to the second 90 degree angle and then checked it with my torque wrench. It checked out at 107 ft/lbs. It seems pretty high of a torque setting, however after talking with Van, he assured me that that torque value probably wasn't too high. Which makes sense due to how tight they were originally, as they were difficult to loosen.
Machine shop checked the head out yesterday morning and they said it was fine. Held vacuum on all intake and exhaust ports. They shop said the plane was fine and the guy was confident that it would be fine to reinstall.
09-21-2014, 05:27 PM
#38
Rennlist Member
Thread Starter
Going to install the head tonight and I will be using the 90 degree method.
09-21-2014, 09:49 PM
#40
Intermediate
To second Van's explanation, the angle method for tightening is better than torque since it results in a more accurate elastic elongation of the fastener. Torque is a rather imprecise method for measuring the clamping (stretch) force developed by a fastener - at the worst end of things the clamp force can vary by as much as 30% for the same torque wrench reading (ref: Lockheed Martin Aeronautics internal research report). This is also why one should pay close attention to the thread lubrication specification for any application. These days, assume clean and dry threads unless lubrication is specified.
09-22-2014, 08:53 AM
#41
Rennlist Member
Thread Starter
^^ Very good explanation!
I got the head on last night and used the proper 90 degree angle method. I'll tell you what, those head nuts are pretty dang tight now. I used my torque angle gauge and had a buddy read it as I was torquing the nuts. Hoping to put the rest of the engine back together today and get it on the road. Not much left to do other than the intake manifold, fuel rail, timing belt, and covers.
I got the head on last night and used the proper 90 degree angle method. I'll tell you what, those head nuts are pretty dang tight now. I used my torque angle gauge and had a buddy read it as I was torquing the nuts. Hoping to put the rest of the engine back together today and get it on the road. Not much left to do other than the intake manifold, fuel rail, timing belt, and covers.
09-22-2014, 09:10 AM
#43
Rennlist Member
Thread Starter
Will do. Van, I appreciate the advice on how to torque the head properly! I had to work the last few days and hadn't had much time to work on the car or to read posts on the forum. Took some time after work last night to get some stuff buttoned up. I can see how you work up a sweat torquing the head. I know I did, lol.