New head studs or old

[malpaslane]

Hi all, i have a 2.7 1976 car , which i had the engine rebuilt about two and a half years ago, everything was great up until a year ago, when what every one agreed was a head stud gone, the car had done about 4000 miles up to that point. It,s taken me a year to take the engine out and strip because i was so pi$$ed that i was here again.
Now i,ve stripped it down i,ve found that the top nut on cylinder number three was loose and none of the bolts seem to be broken.
Now for the questions, should the garage that done the engine have thread locked the nuts (because i,ve found afew more loose) and would they come undone after just 4000 miles and if i,m missing a broken stud and find it when i,ve finished stripping it , should i replace them with the original steel studs or the new style ones as alot of 911 engine books seem to say stick with the old style ones, many thanks for any help . Rik.....

[356RS]

Sorry to hear you only got 4000 miles. it's sounds like the studs are pulling out of the case. It's not uncommon for this to happen on the 2.7 engines with there emission standards and mag case's. Your rebuild should have included case savers installed. But maybe they did install them. If they were installed, you might be lucky and just need to have them correctly re-torque, but you would be really lucky if thats all it is. Also, the head nuts are not thread locked.

[malpaslane]

Thanks 356rs, i never had the bolts done at the rebuild as the garage said they were ok, the reason i ask about the thread lock is i,ve found alot of nuts loose, could my problem be this and not pulled studs?. the same garage is doing the work this time and before it goes to them, i want to make sure it was not partly their fault that i,m here again. what do you think about std steel bolts?. thanks again Rik

[Flat6pac]

The steel bolts are still the problem, you need the 24 dilivars and the case tapped and casesaved. Part of opening the engine and setting the valves is to check the rocker shafts to see they are in place and torque the heads because the nuts do come loose.
Save the steel studs and sell them to a guy with a 3.0 that needs steel studs on the bottom row
Bruce

[356RS]

The reason the nuts are loose is because after the engine warms up and cylinders, heads heat up and expand the head studs get pulled out a little from the engine case. After the engine is shut down and cools over night the cylinders and heads shrink back to normal but the pulled head studs stay at there pulled length so the torque on the nut/stud is lost. You end up with loose nuts. The reason this all started was at one time your 2.7 got very hot or got very close to hot many times. This started the threads in the case to get damaged and not support the required torque anymore.
I don't think that the heads will re-torque now. I'm not 100% sure, I hope I'm wrong, but if they will not re-torque the only way to fix the problem is a complete tear down and have the case stud holes repaired with Time-Serts or better yet Case-Savers.
I can't say anything about your garage mechanic but most mechanics that are familiar with the 911 engines know about the 2.7 model with the emission hardware making things get real warm.
Is your engine a stock 1976 2.7? I should have ask that first.

[4sd911]

All above info is good. The head stud bolts will loosen after first start up, if they were not re-torqued this would explain them being loose. If the stud is pulling it will not hold torque. Do not use thread locking compound on the head bolts. If you can get them to hold torque then try that. Is the engine running bad?

[malpaslane]

Hi All, thanks for all your help, 356RS yes the engine is a stock 2.7 165 bhp, 4sp911 , no the nuts were not re-torqued after the first start up ,the garage never told me about that ,they just told me to come back when the valves needed adjusting after about 3500-4000 miles, as for the running of the car, it ran great after afew little problems at the start, but after that and the valves being adjusted and the car tuned the car ran the best it has even done
The problem started just as i was taking the car off the road for winter, it sounded as if the exhaust was blowing and got louder and made the blowing sound more offen as the outside temp dropped in october just before i took it off the road, i spoke to the garage who said that the heads bolts had probably broke and that they would have to strip it. Now i,ve stripped it down again i,m finding loose nuts, reading afew books (one of which being 101 projects for your 911) i,m reading about using the steels bolts ,is this not the way to go?... Also one last thing, what is the emissions hardware as i have no air pumps or anything like that on the engine or is it something that porsche did to the casings. thanks Rik...

[john walker's workshop]

the 2.7 really needs 24 dilivars with case savers. the cases are weak. steel studs can pull even a case saver on occasion. one main reason that things don't stay tight, is the various mating surfaces that are supposed to be on the same plane as the crank centerline are not, due to wear and warpage over the years. the cylinder base surfaces on the case are usually worn out and of unequal heights. the tops of used cylinders are worn unevenly from the loose heads moving around on them, and the head's cylinder contact surface is all out of wack. these items need to be machined to have a long lasting engine. see if the shop did these things.