CJWing

I just got my hands on a base model 1974 911 that has been sitting for quite a long time. many things need to be fixed or outright replaced and most of it seems straightforward.

however, for the engine, I was looking for replacement cylinders and piston sets and I came across a 2.8L and a 2.9L conversion kit being sold by LNengineering. however, I can't find much documentation on what else needs to be done to the rest of the engine to use these.

I know that special rings and head gaskets would probably be required, but I can't find anything that mentions if I would need to machine the block or the head.

So, are these parts just drop-in upgrades, and if not, what would I need to get the engine running with one of these kits and where can I find the parts that are needed?

theiceman

Thisis one of those can of worm questions that open up to a lot of debate and discussion.

the 74-77 cases were magnesium , and in conjunction with being magnesium , that car had thermal reactors and a small 5 blade cooling fan.

The problem became that the head studs would pull out of the magnesium case , cause leaks and compression issues and all kinds ....

These engines could be made reliable by adding an 11 blade cooling fan, removing the thermal reactors and rebuilding the engine by putting time certs in the magnesium case to stop the heads being pulled out. Then the case would be assembled and line bored to ensure all as true as twisting of the magnesium case at an engineering level would cause issues with the crank.

These are great cars , very light and nimble if you can get one with these issues resolved.... they don't have the weight of the SC flares.

These problems were resolved in the 3.0 litre SC by making the case halves out of aluminum, adding cooling in an 11 blade fan , thermal reactors were replaced by a catalytic converter mounted downstream and making the studs out of Dilivar which expanded accordingly in order not to pull ( these had issues of their own , but that makes for a different thread )

Now that we have the background we have to think about your car .. i would think you have to make sure all the above is done , before you start bolting on bigger go fast bits.

So i think your first thing would be to research stud pulling in 2.7 litre engines. it could certainly be a great project but i think the machine shop work involved could get spendy.

CJWing

Thanks for the info about the Thermal Reactors, I haven't yet seen anything about that, and I'll make sure to get them off if the car has them, I'll also start researching the stud pulling. And look at getting an 11-blade fan.
As soon as I can get the car into my garage I plan on pulling the engine apart to see what needs to be replaced, since the previous owner (my grandfather) said it had bad rings I'm just assuming that it'll need new cylinders.
but the current plan (without knowing the exact condition of the motor) is to at the very least, replace those and possibly get higher compression pistons since LN will do the twin plug modification on all 6 heads for 475, I'll also have them do valve seats and guides.

theiceman

Charles Navarro is a very knowledgeable guy , and i would suggest talking to him about what i wrote here. he should know all about it. he might be able to suggest a direction.

i would also recommend Wayne Dempseys engine rebuilding book if you don't have it already .. worth its weight in gold if you do your own engine work.

Wayne is the former owner of pelican which is the place to be if you are puling your engine apart. They even have a specific engine rebuilding forum.

https://forums.pelicanparts.com/911-...uds-2-7-a.html

rstarga

A 2.7l with nikasil cylinders and 9.8 compression pistons is a very sweet running engine. Anything above and you'll need twin plug. If you want more displacement get an aluminum block. More reliable.
Any mag block will be better off with the mods mentioned above. 2.8 and 2.9 are not just a drop in.

TonyVan

The 1974 911 did not have thermal reactors. Not sure about the fan. The ‘74 is considered the best of the 74-77 cars. Take a look to see if it has the oil lines for hydraulic tensioners. Most of these engines have been upgraded over the years and are fine running engines. The CIS system, when properly running, is reliable and fuel thrifty. I have a ‘74 Targa and have driven it back and forth to Texas, yearly, for the Hill Country Rallye. It’s been a blast and the 2.7 is quick revving and light. Before you embark on a long expensive project, get the car running and have a compression and leak down test preformed. You may be surprised by its condition. If you do decide to rebuild, check out Al Kosmal in Washington or Supertec Performance in Ca. Both are well versed in building killer engines based on the 2.7. Al is currently doing mine with stock displacement but modern EFI and other performance upgrades. Both usually post on Pelican Parts bbs. Lots of pictures of their current builds. Good luck with the revitalization of your ‘74.
Tony

theiceman

Tony did you put time Certs in your original Magnesium case ?

TonyVan

Engine had a full rebuild once with the previous owner and a top end during my ownership. First rebuild included all the recommended upgrades. Had the top redone after pulling a head stud after a long track day where I was foolishly running well past its red line. I’d removed the rev limiting rotor and wasn’t paying enough attention. Having too damn much fun. Al Kosmal has the engine, now, for its current transformation. Al posted some pictures today on Pelican. You should contact either him of Henry at Supertec. They’re up on all the latest.
Tomy

Spyerx

What’s your budget? Follow my link on tang.

full send 2.8 mag case build. Costs are eye watering. To do it right you do it all.

hauls ***.