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1974 low mileage 2.7 - case saver / front oil cooler ?

I'm looking at at low mileage (under 40k) original engine that has not had the head studs break YET and doesn't have the additional oil cooler. The engine runs great, has tensioner updates and has good compression / leak down #s. My question is this. Will putting the front cooler in to keep the engine temps low help to push off the seemingly inevitable broken head studs? Also, is it easier (more cost effective) to pull apart the engine now and put case savers in - before an issue arises? It's a strange car, with remarkable low mileage and a lot of fun potential, but all I read about is a $14k engine rebuild that is only a matter of when and not if. Is there any way to avoid it?
Thanks
Wyatt
Old 06-12-2016, 12:34 PM
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Wyatt,
Greetings. The mid-year 2.7 engine was not known for breaking studs, but for the studs pulling out of the mag cases. To my knowledge this was caused by the differential of thermal expansion between the Dilavar head-studs and the aluminum heads. Basically this would result in the head-studs no longer being torqued down and the heads coming loose. It is not clear to me the % of 2.7s that this happened too, but the likelihood of it happening was increased the use of early pollution devices/thermal reactors, which increased the heat on the exhaust side and was further aggravated by the use of the car in warmer climates.

Your 74 however, used the early header/heat exchanger design and was never subjected to the dreaded thermal reactors and the added heat. A front oil-cooler will only improve this situation.

Due to the low mileage and good compression and leak-down tests, i would recommend that you check that the headstuds are still torqued down properly.....if they are tight and torqued to spec, I'd leave all as is and have fun with it...checking the head-studs at oil changes to keep on top of and changes....but if they are loose, i'd drop the motor and time-cert the case.

Note: even though it is a low mileage engine...i'd check to see if the case has already been time-certed.

regards,
al

PS: last two 3.0s I've rebuilt had broken head-studs.
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Old 06-12-2016, 02:15 PM
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al,
Ok, that is making more sense now. I've just finished a 912 after years and years of slowly bringing it back to life, so now on to the 6 cylinder. I'm 90% sure it hasn't been certed, but I don't know of anyway to check without taking the heads off... is there a way? In the scenario where they are not torqued, I drop the engine myself and bring it to a shop to pull the heads and case saver/ time-cert it - what kind of $$ would that run in your experience? Ballpark.
Thanks
Old 06-12-2016, 03:07 PM
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http://www.olliesmachine.com/uploads/Ollies_Price_List.pdf

Ollie's price list is a good reference for machine work.

regards,
al
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Old 06-12-2016, 03:32 PM
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studs.

If you remove the block off or duct plate, you should be able to see where the rearmost studs for cylinder four where they enter the case and be able to determine if there are time-certs/case-savers.

If you can see an annular ring of a slightly larger diameter than the stud threads outside diameter....you are in luck.




regards,
al
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Old 06-12-2016, 06:06 PM
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Much appreciated! Out of town at the moment, now even more ready to be home.

W
Old 06-12-2016, 06:31 PM
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Got to clear up a couple pieces of info.
The 74/77 came from the factory in 2.7 form as mag case with steel studs and aluminum cylinders.
As the engine warmed for years the aluminum cyl would expand faster than the steel studs. The weak spot was the magnesium case. The studs pulled on the magnesium.
On a 2.7 the studs are able to be seen running on the outside of the cylinders. The magnet will test there for steel.
The fix for the 2.7 is case savers and dilivar studs. The expansion of the aluminum and dilivar for all practical purposes is the same.
If you don't have a problem with the engine, why look for one. The 74 is the least likely to have stud failure. No thermals or 5 blade fans.
Bruce
Old 06-12-2016, 08:01 PM
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A front cooler is a good idea. A Carrera style cooler is the best all around.
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Old 06-12-2016, 08:21 PM
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Quote:
Originally Posted by Flat6pac View Post
Got to clear up a couple pieces of info.
The 74/77 came from the factory in 2.7 form as mag case with steel studs and aluminum cylinders.
As the engine warmed for years the aluminum cyl would expand faster than the steel studs. The weak spot was the magnesium case. The studs pulled on the magnesium.
On a 2.7 the studs are able to be seen running on the outside of the cylinders. The magnet will test there for steel.
The fix for the 2.7 is case savers and dilivar studs. The expansion of the aluminum and dilivar for all practical purposes is the same.
If you don't have a problem with the engine, why look for one. The 74 is the least likely to have stud failure. No thermals or 5 blade fans.
Bruce
Bruce

Yes,
thanks...I may have not stated this perfectly earlier and may not state it perfectly now...... The use of dilivar studs or alternatives goes round and round, but.......Dilivar studs were the early factory fix and an attempt to address the problem of pulled studs/mag cases by matching the expansion rate of aluminum. However, I don't believe that fix was a success, as the early Dilivars suffered from failures (cracks, hyrdrogen embrittlement, breakage, whatever) and over the years have been superceded and changed many times with plating, coating, etc. The lower Dilivar studs on the 3.0 and later do not pull out of the stronger aluminum case......they now seem prone to breakage. and then are often replaced by Arp/Supertech/Raceware alloys (expansion rates closer to steel than aluminum I would venture) or even the 993, full threaded , latest version of Dilivar hmmmmm......or .......steel studs.

I think that Wayne Dempsey summed it up well in his "How to Rebuild and modify Porsche 911 Engines' book...as follows:

"In Chapter Four of my Engine Rebuild Book, I discuss the infamous 911 head stud problem extensively. The bottom line is that I recommend that you should replace the lower Dilavar studs with the standard original steel studs that have been used for years on the earlier cars. Doing so seems to have resulted in no problems, and has also solved the Dilavar stud snapping problem. In the past the quality control on the Dilavar studs was so bad, that there were many stories about Dilavar studs snapping when they were tightened down at rebuild time to factory specifications. Needless to say, the risk of installing Dilavar studs seems to be much higher than I personally would feel comfortable with. My recommendation is to stay away from these studs, and use the early steel studs for both upper and lower rows of studs, for all engines from 1965-89.
In a nutshell, the 911SC engines should have their lower exhaust studs replaced (the upper studs that were used were the standard early steel ones). You will need a total of 12 to replace these. The 911 Turbos used Dilavar studs for all of the cylinder studs - upper and lower. You should replace these with the standard steel ones (a total of 24 needed). Pre-1978 911 USA engines don't need to replace any head studs unless the threads are damaged.
There is however, another alternative to the original steel studs. A company in Michigan called Race-Tech Engineering manufactures what are commonly known as Race-Ware Head studs. These studs are well known for their aerospace quality and construction, and have a reputation for being bulletproof. Their major downside is that they are expensive – almost double the cost of the plain steel head studs. If you have a somewhat unlimited 911 engine rebuild budget, then I would use the Race-Ware head studs. If not, then the original steel studs should work fine. [Rebuild Book: Page 83]

regards,
al
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Last edited by al lkosmal; 06-13-2016 at 08:06 AM..
Old 06-12-2016, 11:37 PM
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I don't want to thread jack, but is this what an insert looks like on a non clean engine?
I'm not sure what's normal and what's an update. I took this picture on my engine on the stand.

And yes I will take off the fan shroud and clean up while its out of the car.
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Old 06-13-2016, 07:17 PM
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That certainly looks like an insert to me.

Another question, if head studs are not to torque can they not be set back? Is it a matter of the head studs very quickly loosing torque once they have backed out? As I put miles on the engine (because I drive these cars everyday) if I'm on top of torque specs often would I generally be alright or will I just loose power and leak and have to surrender very shortly after I notice a head stud loosing torque and backing out. ?

Last edited by submerge; 06-15-2016 at 03:17 PM..
Old 06-15-2016, 03:13 PM
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they lose torque because the stud is pulling out of the magnesium/pulling the threads in the mag case out......so, you may get lucky, if the threads are not totally hosed, but it's likely if they've pulled once, they will just pull again if not properly fixed with a case insert.

regards,
al
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Old 06-15-2016, 04:09 PM
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Pulling the threads out... yes that seems obvious now. Thanks!
Old 06-15-2016, 07:16 PM
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I hope that this is not a hijack, but rather an addition to the discussion.

Although I have not verified this yet, I recall that my studs seem to be threaded into inserts.

However, I am clearly pulling an exhaust stud, because the nut loses its torque very quickly - after a few hundred miles.

Is it possible that I am actually pulling out the insert? If this is the case, am I in the market for a new crankcase - or different engine?
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Old 06-25-2016, 02:02 PM
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studs

The exhaust (and intake) studs are threaded into the head, not the case. I would think that would be easily fixed with an insert (I would double check that you have inserts for the exhaust studs) or repaired ....and if not, you would need a new head or , not a new case.

see illustration below:

part # 5 on the bottom is the exhaust stud and #6 on the top , is intake.


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Old 06-25-2016, 02:49 PM
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Quote:
Originally Posted by al lkosmal View Post
The exhaust (and intake) studs are threaded into the head, not the case. I would think that would be easily fixed with an insert (I would double check that you have inserts for the exhaust studs) or repaired ....and if not, you would need a new head or , not a new case.

see illustration below:

part # 5 on the bottom is the exhaust stud and #6 on the top , is intake.


Sorry, I was not clear. I'm talking about the exhaust side head stud (passing through the head), not exhaust studs. One head stud, on the exhaust side of the #6 cylinder is pulling from the crankcase, thereby causing its nut to come loose. It may be pulling an insert out of the crankcase.
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Old 06-25-2016, 04:37 PM
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