2.7 Repair using timecerts

[Tennessee911]

I have a 71 911 with a 74 2.7 engine. Runs strong. Car is not tracked and driven less than 1k miles per year. Have no history on engine repairs. Has external front oil cooler.

I have Wayne's books and aware that he recommends case savers. The head bolts are backing out thru the nuts with little depth left in the nuts to re-torque the heads.

Local respected independent tech says he can tear down to piston cylinders and not split the case and do time certs. Says he has great success for years doing this. With new studs about $3k total.

Has anyone had success with this on a mag case? Would prefer to put the money toward a 3.0 but it is worth some amount of money to have car back drivable. I would attempt a rebuild but I have a 61 356 engine torn down and part of my 61 Notchback--hoods, doors, etc in the other side of my undersized garage.

Don't need to post that I need to rebuild it right as I don't think it makes $ sense. It's worth $1,500 or so to have the car to enjoy driving in 2012 while I work on the 356.

Looking forward to the discussion and thanks.

[Steve@Rennsport]

Case savers, in this application, work FAR better than Timeserts.

[Eagledriver]

If you are working on it yourself, you have little to lose trying it. Timecerts were used for years with success and were even recommended in books. I think it's a great idea to not split the case.

-Andy

[afterburn 549]

The worse that can happen is you get to do it a second time.......................

[CaptainCalf]

I've used timecerts for head bolt holes in my alum 3.3 case and I think they're great.

Additionally, IMHO $3K for an experienced mag case wrench and new studs sounds fair considering the amount of work that will be done...RC

[notmytarga]

Originally Posted by Steve@Rennsport

Case savers, in this application, work FAR better than Timeserts.

Steve,
My 2.7 case was rebuilt in 2007. Porsche machinist did case evaluation, oil bypass, shuffle pinned 2 center webs and installed timecerts. He uses Timecerts because the Casesavers, being of greater diameter, encroach on the spigots too much. He doesn't see failures. Perhaps I missed something discussed here after my rebuild interest. Steve, does this recommendation deserve an underline and a bold? The machinist wasn't a putz AFAIK.

Doing the headstud case improvement without splitting the case would be a compromise. Perhaps the mechanic can describe what measures he uses to assure milling material does not enter the case - he may have it figured out. Handdrills not allowed.

[VitoV]

For the record, they are called Time-Serts. Think of "insert", not those little candies that freshen your breath. Not trying to be a pedant, just making sure this thread shows up in a forum search...

Originally Posted by notmytarga

Perhaps the mechanic can describe what measures he uses to assure milling material does not enter the case - he may have it figured out. Handdrills not allowed.

Applying heavy grease to the drill and the tap, and going slowly in each operation, is probably the only reasonable approach. There's a certain amount of risk, but that's inevitable I think. If by "handdrills" you mean power tools, you are probably right-- this operation is going to be entirely by hand.

Doing those stud holes in situ sounds like a pain, though at least the cylinders will act as nice guide blocks to keep the drill and tap perpendicular.

[BURN-BROS]

I just talked to a friend at another shop that has a mag case with time certs that are failing....

The mag cases are very old now and the material does fatigue.

[Lorenfb]

"If you are working on it yourself, you have little to lose trying it."

- eagledriver -

Rather a naive statement, as one can possibly damage the case.

[bassfishman]

My 2.7 had to be split!

[Henry Schmidt]

Over the years I've seen limited success with the used of Time-serts.
The issue seems to be the thread pitch (the Time-sert thread pitch is too fine for the soft magnesium).
With the CaseSaver you have a plethora of sizes and thread pitches available to address our mag case head stud dilemma.
Beyond the thread pitch issue, I see DIY builders install Time-serts in an erratic fashion.
I call this phenomenon "Porcupine studs". The studs are installed by hand and more than a few inserts are installed askew making cylinder installation difficult if not impossible.
I have even seen this issue further exacerbated by bending the studs into positions. As you might imagine, the only proper cure is the removable of the poorly installed inserts, then installing an over sized CaseSaver.
The issue of "spigot encroachment" really isn't what it sounds like. The insert doesn't actually protrude into the spigot as much as it deforms the material adjacent to the insert.
This issue is remedied by a clean-up pass in the spigot with a boring bar. Most qualified machine shops perform this procedure and spigot decking as part of the CaseSaver process.

The Time-sert is a wonderful invention that makes thread repair at home quick, easy and affordable but for mag case head studs issues, professionally installed CaseSavers are the best option and well worth the peace of mind. IMNSHO