Need help from engine builders
 

I recently rebuilt the engine in my 1980 911SC. I did a top-end rebuild down to new rings and piston base gaskets. Nothing connecting rod or below was touched. I completed the build two weeks ago and first got the car running on Monday, 3/12. Everything sounded and seemed fine until I heard louder then normal exhaust-type noise on full throttle acceleration. This began after about 300 miles of breaking in and was heard on the track at VIR. Perhaps I should have waited longer before going to full throttle, but I was still short-shifting at about 5000 rpm.

I have thoroughly checked the exhaust (factory headers and Monty 2-in 2-out) and find no leaks. However I do find dark, gooey liquid around the head to cylinder interface. It appears to me that I do not have a good seal between the heads and cylinders and that combusion air/fuel is escaping on the power stroke. #1 is the worst. #3, #4, and #6 also appear to be leaking. The heads were machined .010" and their surfaces are perfect. I did nothing to the cylinders other than clean them and scrape the carbon out of the groove for the head gasket. I used new head gaskets (C-E Rings?).

If any of you have experienced this, have you tried re-torqueing your head studs? How much can you torque them? This is an SC aluminum (930) case and has all new steel head studs (old style. Same as the original ones that were on the intake side.). I re-used the washers and nuts. I torqued them the night I installed the heads and re-torqued them the next day.

I would really like to try re-torqueing the heads if there is any chance I can re-establish the seal. Not looking forward to pulling the engine and tearing everything apart again. I would also like you thoughts on what I may have done wrong.

Thanks,

Don Bryant
'80 911SC

Don,

What type of torque wrench did you use? On my first rebuild I used the clicker type wrenches that had been "calibrated" by a machine shop about six months previous. Yeah, "calibrated"... I personnally checked them after my engine started leaking. calibrated... One was waaaaaayyyyy too light (the smaller one) and the larger one was waaaaaayyyyy too heavy. I bought another t-bar wrench and re-did the whole thing. I also used Dirko on the second time around (thank you JW!!!).

Try testing out the torque with a different wrench than you used for the build. Preferably a t-bar style.

David,

Thanks for the help. I am hoping this is a torque problem and not a problem with the mating surfaces or the C-E rings. I am planning on loosening the head nuts, lubing nuts and washers, and re-torqueing. I am also going to check my torque wrench against a couple of othetrs.

Don

I am pretty sure I have found the problem. It is two-fold: I did not properly lubricate the washers, nuts and threads, and my torque wrench is reading about 20-25% higher than it is actually putting out. I am going to re-torque tomorrow night and see what happens. I followed the torqueing procedure in Wayne Dempsey's book.