911 2.7 top end rebuild with a twist - Inserts without splitting the case?

[Alexandphoto]

Sadly my 76 2.7 has pulled some studs. I’ve spoken with a local machine shop who is used by a number of big name shops here in Sydney. He has suggested that since my case was not leaking oil from anywhere other than cylinder 2, he could install case savers without splitting the case. He’s performed this before.

My engine had a top end, with no inserts, by the previous owner 30 years/20k miles ago and now the head studs have pulled. All but 1 on cyl2 could torque back to spec (cyl2 gets close to spec but keeps turning).

I have good oil pressure, no oil leaks (aside from cyl#2 with the pulled studs), and on a dyno it recently made good power so I don’t believe there are other issues.

Questions
- Does anybody have experience with performing a top end and having inserts put in without splitting the case?

- Is it common for the mating surface on the case to warp where the case and cylinders meet?

- I’m going to give the rest of the top end a go myself as I’ve tinkered a bit inside other engines, and there’s a wealth of information out there for this. Aside from the “how to rebuild” book, are there any other resources people recommend?

- I currently have Weber 40s so I’m looking at also upgrading to 9.5:1 JE pistons and E cams instead of the stock CIS ones. Anything that I should be concerned about before going down this route?

- are Supertec studs still preferred over stock studs for the 2.7s?

- what else is good to do with the engine out? I have clutch on the list and I’m considering a lightweight flywheel too. Any sensors or other parts that are worth doing at the same time that are difficult with the engine in the car?

Thank you for any insights in advance!

[rwest]

Hi,

No help on the engine questions, but when it is out, fuel lines in the tunnel and the trailing arm bushings might be a good idea.

Lightweight flywheel on a street car might not be a good idea- ask around.

Transmission to ground strap is something to check/replace when you put it back in.

[Bobboloo]

You need to split the case because if your studs pulled then your case needs the line bore cleaned out at the very least. The reason the studs pulled was because of excessive heat cycles. That wreaks havoc on the case which goes out of square. If it's not too bad you can just run a standard bore to clean it up and use standard bearings. If it's excessive then you need to shave the case halves and then rebore the mains and intermediate bearings.
Besides it's not possible to do head stud inserts properly with the case halves mated. The case halves need to be milled for the insert to go in straight. Maybe your mechanic has a trick to doing it but I've seen cases ruined by doing this job without the proper tools.

[Bobboloo]

On the question of the mating surface to the cylinders. Yes, that surface should be "decked". For the same reasons I outlined above.
Since you're going to carbs the engine will run cooler which is a good thing for it's future longevity. E cams are a nice choice if the ports are 32mm (2.7 normal). If the engine is a 2.7S CIS then the ports are 36mm in and you can go with a more aggressive cam like a Mod S (more lobe separation) which has a wide torque curve like the E but makes more power.

[eisenbud]

We inserted hundreds of these in the '80s and '90s without splitting the case. You need to remove the rods and tape up the oil gallery holes on the crank, set the case up on a mill, we used two old cyls. and shimmed it so it was true to the chuck and sealed the case up really well. You can make plugs for the open cyl. bores out of card board and tape, vacuum it off before you open it up again and flip it over. The cyl. sealing surfaces will need to be flattened when you are done so just remove .25mm and either add a additional shim or use a single .50mm shim. The engine is dry sump so if a stray piece of magnesium does go in the case undetected it will get caught in the oil filter. We have never had a single problem doing it this way. If send me your email address and I will come up with a few pics. of our set up and give you some more tips. eisendudsinc@gmail.com

[Alexandphoto]

Originally Posted by rwest

Hi,

No help on the engine questions, but when it is out, fuel lines in the tunnel and the trailing arm bushings might be a good idea.

Lightweight flywheel on a street car might not be a good idea- ask around.

Transmission to ground strap is something to check/replace when you put it back in.

Great suggestions there, I’ll add those to the list. I run a lightweight flywheel in another non-Porsche car without issue, is there a difference in behaviour for our P cars?

Originally Posted by Bobboloo

On the question of the mating surface to the cylinders. Yes, that surface should be "decked". For the same reasons I outlined above.
Since you're going to carbs the engine will run cooler which is a good thing for it's future longevity. E cams are a nice choice if the ports are 32mm (2.7 normal). If the engine is a 2.7S CIS then the ports are 36mm in and you can go with a more aggressive cam like a Mod S (more lobe separation) which has a wide torque curve like the E but makes more power.

Thank you for the insights on your posts. I’m still on the fence with the power modifications planned. The Webers are already on board, but I’m torn whether I go for SC cams or the whole hog and do JE pistons with hotter cams. I wasn’t unhappy with the power before, but a bit more might not hurt…

With the 2.7s it sounds like opening Pandora’s box to split the case. That’s what I’m hoping to avoid, especially as my motor had no other signs of issues (leaks, power, pressure, smoke etc.)

Originally Posted by eisenbud

We inserted hundreds of these in the '80s and '90s without splitting the case. You need to remove the rods and tape up the oil gallery holes on the crank, set the case up on a mill, we used two old cyls. and shimmed it so it was true to the chuck and sealed the case up really well. You can make plugs for the open cyl. bores out of card board and tape, vacuum it off before you open it up again and flip it over. The cyl. sealing surfaces will need to be flattened when you are done so just remove .25mm and either add a additional shim or use a single .50mm shim. The engine is dry sump so if a stray piece of magnesium does go in the case undetected it will get caught in the oil filter. We have never had a single problem doing it this way. If send me your email address and I will come up with a few pics. of our set up and give you some more tips. eisendudsinc@gmail.com

Very helpful, thank you for that. Can the sealing surfaces be done without splitting the case though?

I’ve sent you an email, hopefully you receive it?