964 - Repeat of Head Stud Woes

[Porsche_monkey]

Factory bolts should bottom out, and they should have 5.315" exposed. Aftermarket bolts (ie Raceware) say not to use loctite (unless inserts are used), factory bolts should have loctite (red).

With red-loctite on the studs they will not be driven in any further when the barrel nuts are installed. I can foresee issues with Raceware bolts (installed without loctite) being torqued too tight into the case as the barrel nuts get tightened, but I suspect that is rare.

Personally I would use a bit of loctite on any head stud to ensure that it does not get bottomed out.

"The reason any stud pulls out on the early or late engines is because some idiot probably bottomed out the stud in the case when he installed them"

I can see no logic in this statement, and perhaps there isn't any. I would like to see Henry chime in on this issue, if his suggestions differ from mine I will defer to his experience.

[captek]

I always use the red permatex thread locker,when this stuff sets up you have to heat the area up to get the stud out.I would not put in any stud without the use of thread locker.Even epoxy would be good on the studs.

[Jim2]

"The reason any stud pulls out on the early or late engines is because some idiot probably bottomed out the stud in the case when he installed them"

Generally speaking, if a stud were bottomed, and then tightened significantly, this would place preload on the case threads. This preload compounded with head nut torque and thermal expansion load would potentially cause the case threads to yield.

[oemexp]

"The reason any stud pulls out on the early or late engines is because some idiot probably bottomed out the stud in the case when he installed them"

1) This statement makes no sense
2) I work with PMNA folks all the time and there are several people there who don't go near the mechanical side of the motors and could have made a statement such as this
3) A proper casting/stud design always includes a blind hole that is of proper depth to bottom the stud to lock the stud into place. Otherwise, the stud is removed during normal disassembly and nut removal which defeats a major advantage that studs provide.
4) Locktite should be used to install so they are locked better and they can be heated later to remove the studs as necessary. Epoxy will be much harder to work with if they need to be removed.
5) Obviously if manufacturing drift caused the holes to be drilled too deep, the stud length adjustment is most important and the locktite is an absolute must at that point.
6) Thermal expansion of the engaged threads in the case won't affect any of this since thermal growth happens as a percentage of length. The total length of threads is so small that you are only talking about microns of growth across the length of threads in the case. This is not going to cause thread failure.
7) I like Steve's recommendation to use steel on smaller better thermally controlled engines and get back to the best DV studs you can buy for bigger or more powerful (less thermally stable) engines. DV needs to be painted or plated to keep corrosion under control also.

Mark