Magnesium cases & reliability
 

Guys,

I have a broken 2.7 CIS (I know, I know...) My understanding is that the 2.7 has tons of problems, but 2.4 S motors are great. Both use mag cases, but the 2.7 has the stronger 7R case. But, everyone says these motors are junk, you have to get an aluminum case (3.0 preferred).

Here's my question: horsepower aside, can a 2.7 CIS with an original, unbuilt case be reliable? The 2.7 has less compression & runs at less rpm than a 2.4S, and if you do all the right things to keep it cool (11 blade fan, SSI's, no sound insulation on the cylinders, and a good oil cooler), why shouldn't it be reliable?

Here's my dilemma: I have maybe $3k to $4k max to get my car back on the road. My top end is great, so one of my cheapest options is to bolt together a 'good' 2.7 bottom end with my top end, injection, ignition, etc. Would this be nuts? If not, does anyone here know of a good 2.7 bottom end sitting out there someplace?

Thanks,
David

I would look around for a 3.0 cis for the money you have available. Continuing with the 2.7 may lead you back to your dilema. An running sc engine is in the 3 to 4 thousand range(or at least all I would spend on one).

There is more reasons that the studs pull on the 2.7 than just heat. It also is a bigger bore (about 15% more force?) and isn't the spacing between the studs and the bore in the case also less?

I think there is no way around putting a magnesium case that has been completely redone by a reputable machineshop. You will waste your time and efforts on a case that hasn't been properly rebuilt. Either your case or another one. I think it isn't that expensive to have it done, if you check in Wanye's book. If your pistons and cylinders are good, you definitely can get this done within your budget.

I doubt 4k will buy you a decent 3.0 (e.g. from a wrecked car with a warranty). Of course you could offset the 3.0 cost with selling some of the 2.7 parts that are good. And there is always private sellers (e.g. club members or friends) that may have a decent 3.0 for less.

Cheers, George

Turbo Dave,
The 2.7 and the magnesium case can be a reliable motor. My experience for the last six years racing my '76 has been positive. If you do all the right things you pointed out, along with some time certs and ARP bolts there is no reason you can't get a reliable motor for the money you want to spend.
The magnesium case problems were made worse by the thermal reactors and the poor decision to switch to a five blade fan. This along with all the new smog rules, resulting low power, hot motors, gave this series of motors a poor reputation.
I don't know what happened to your motor, but don't be afraid to get a good magnesium case and put it back together again.
There are lots of people out there that are very familiar with this motor that can help you.
If the motor is really badly broken, that is crankshaft and piston and cylinder problems, it might not be economical to get all the parts together to do a rebuild. In that case I would look for a good 3.0 or 3.2 motor, but it will cost more than four grand.
Bottom line if you get lucky and find a good short block for around $2500 it may be possible. Good Luck,

Dave, I'm just wondering what the "sound insulation on the cylinders" is ? :confused:

Having torn down a few 911 motors and rebuilt mine, I can say w/ a great degree of certainty that there is no such thing. There are small baffles that direct the cooling air around the cylinders, but they have nothing to do w/ sound and you most certainly do not want to remove them if you are trying to keep the motor from over-heating and grenading!! :eek:

Other than that, I see no reason why you could not build a strong 2.7. The challenge is to do it for less than buying a good 3.0, as you know. Good luck! :cool:

I am going by personal experience. $4500 for a 3.0 with a 915 tranny . Runs like a champ. Just try to get a leak-down done on it before you buy.

Do not despair.
I can build any engine I want and I chose to rebuild a 2.7 for my own car. A 76 912E

Money is almost always an issue.
We will rebuild your 2.7 for $4500 if the top end is truly in good shape.

We will also warranty it for 2 years unlimited miles.
Give me a call.

http://forums.pelicanparts.com/uploa...1088020649.jpg http://forums.pelicanparts.com/uploa...1088020666.jpg

TURBO DAVE,
After reading a rather good discussion on another thread about Time-Certs versus Case Savers, I have been convinced Case Savers installed by a knowlegable shop are superior to Time Certs for magnesium cases. Henry Schmidt presented a very convincing argument for the Case Savers. However when he inserted pictures of both, it becomes obvious which is better. Thanks to Henry for sharing his vast knowlege on this board.

AS stated above and do all th updates you will not have any problems
B.tdT...

( my biggest problem now is is how to get the clutch to hold)

turbo dave, I have the exact same problem good topend with pulled studs, I found a good buttom end on the web board from unclezak, all the up grades turbo oil pump low running time $1400 and it looks great with new everything like he said, rs spec bottom end, and will be putting my top end on it, and a front fender mounted oil cooler to keep it cool Buy the time I get it all done I should have about $2000 to $2500 in it depending on what I will need to do to the topend to make it perfict

READ THE FORUM RULES BEFORE YOU POST - NO CROSS-POSTING ON THE TWO FORUMS!!!

:mad:

-Wayne

Whoa.:eek: That was a bit of an outside voice now wasn't it?