2.7 Engine Rebuild Questions

[KMoore68]

Hi,

I was hoping for some input from the Pelican brain trust on my plan to rebuild the 2.7 engine in my 1977 911 S Targa.

I purchased the car about 8 years ago via BaT and in the auction description, the previous owner indicated the engine had been rebuilt. The previous owner provided a bunch of receipts for things that have been done to the car however there wasn't anything to support an engine rebuild.

About 3 years ago, I had a compression test done on the car and cylinder 5 was low and seemed to be leaking past the rings. At that time I decided to keep driving it until a rebuild was required.

The car has 193000 miles and recently I've installed SSI exhaust headers and completed an EFI and ITB conversion. The car has been running ok with the tune however it has started to blow more blue smoke and generally the car feels like it is struggling.

My target for the car is a low 200 wheel horsepower driver that I can take on the occasional auto-x day but mostly just enjoy driving it around town.

I am planning on doing the tear-down and rebuild myself, I have the books on rebuilding a Porsche engine.

I talked with Henry at Supertec and discussed a few options:

1. Henry mentioned they can provide a conversion that will bump the displacement from 2.7 to 3.0 litres but retain the stock crank and case. This seems like a pretty good solution and could be a cost-effective strategy. Has anyone done this before or have any feedback?

2. Henry also mentioned just increasing the compression to around 9.5:1 via some new pistons. I don't plan on twin-plugging the heads so this also seems like a good idea.

3. I emailed John Dougherty to discuss camshafts because I find the options a bit overwhelming. Am I correct that the DC40 design would be a good compromise for my build. I'm looking for something with an optimal power band in the 3500 - 5500 RPM range.

4. My 2.7 has, I believe, 47mm journals and I believe I'd need to get my cam towers drilled to support the extra oil. I'll need to confirm this once the car is apart.

5. I plan on getting my heads rebuilt locally, I don't believe there is any reason to go crazy on the springs or anything. Is there anything I should be aware of?

6. I plan on getting the crankshaft refinished locally also, outside of micro-polishing, what else should I look at getting done?

Lastly, I am located just outside Vancouver, BC Canada and will plan to send the case to either Ollies or Supertec to get it align bored and possibly have the case savers installed

Anything else I should be thinking of?

Thanks for looking,

Kevin

[targa72e]

There is a dyno in my thread below of a 2.7 with Elgin Mod S cams (very close to DC 40). Specs for engine are listed.

https://forums.pelicanparts.com/porsche-911-technical-forum/1151593-dyno-summary-testing-early-2-4l-2-5l.html

John

[PeteKz]

There are several premium Porsche shops near you. John Walker and Al Ikosmal are in Marysville WA, and one in the Vancouver area (can't remember his name at the moment). I mention those because shipping stuff from Canada to the US and back again will incur a significant expense. Better if you can deliver the case crank, etc. to one near you.

Whoever you decide to use, whether local, Supertec or Ollies, try to stick to one to do the machining and supply the replacement parts, cams, and advice. BTW, case savers/inserts are a must-do in the magnesium cases and should be done by the same shop machining the case.

[Jeff Alton]

Kevin, just checking to make sure you saw my response to your email.

Cheers

[Henry Schmidt]

Originally Posted by PeteKz

...edit...
Whoever you decide to use, whether local, Supertec or Ollies, try to stick to one to do the machining and supply the replacement parts, cams, and advice. BTW, case savers/inserts are a must-do in the magnesium cases and should be done by the same shop machining the case.

This is a misconception. CaseSavers are an option developed for air cooled Mezger cases because of high temps in large spigot engines. The only way head stud pull in Mezger cases is when you bore the spigots or the engine sees excess head temps.
The reason why the stud started pulling was as you bore the spigot, the material near near the head stud is reduced, reducing the structural integrity around the threads.
We very rarely see head studs pull on any early case unless high heat or large spigots exist. Keep in mind that every 2.7 between 75-77 sold in California came off the showroom running temperatures over 240. With the thermal reactors in tact, you could actually see the ground glowing red when you parked your car. Those 1800 degree thermal reactors actually caused the head tempts to go up after you shut the engine off.
Make sense actually, the fan would stop and the heat would radiate upwards.