2.4 liter t

[47silver]

do all magnesium cases need align bored when split?
we have my son's 72 on an engine stand it has 82000 miles on it, i was thinking of putting rings not splitting it, but,,,,,while we have it apart,,, i figure new bearings etc...and prefer not to have to wait on the machining to get it back together...
so my question is if we split the case will it need align bored?

[cmcfaul]

My extremely experienced Porsche engine builder says no. He has built dozens of early 911 engines, including mine without align bore. A ton of others on this board will not agree.

Chris
73 911 E

[RedCoupe]

Everything that I've read says that it has a lot to do with the temperature that the engine has run at over its life. The presence or absence of an external oil cooler and how and where it has been driven all can make a difference. Has the engine ever pulled any head studs? If yes, this could be a clue of overheating in the past. Also, before thinking about splitting the case, you can remove the rod bearings and inspect the crank journals and the bearing shells. This should give you a clue if you need to delve any deeper.

[Steve@Rennsport]

JMHO,

I've never seen any mag-cased engine that didn't require a line-bore to ensure that the crankshaft doesn't bind after rebuilding. Failure to do so results in excessive main bearing wear so if this isn't in the budget, I would not split the case.

[47silver]

i guess the safest route is the machining.

[porschetub]

Originally Posted by Steve@Rennsport

JMHO,

I've never seen any mag-cased engine that didn't require a line-bore to ensure that the crankshaft doesn't bind after rebuilding. Failure to do so results in excessive main bearing wear so if this isn't in the budget, I would not split the case.

Steve interested to know why this is the norm for the early motors,thought this was more related to the later motors 2.7 in particular (small fan and all),if the op isn't puking oil from the case seam or having oil pressure issues he should be fine with a 82k miles for a top end rebuild,there could be reasons that we don't know to the contrary.
Not a question on your knowlege as that appears to be well founded,thanks.

[Henry Schmidt]

Over the years, we have developed ways to measure parts accurately to determine whether parts need to be replaced, reconditioned or just inspected and cleaned.
There are indeed some "rules of thumb" that guide our evaluation of parts but there are few absolutes when it comes to aline boring a case. Over the years (and still today) we have seen many mag engine cases that did not require aline boring.
Heat is generally the key factor.
Early mag cases that developed low heat generally measure out pretty straight by that I mean well within usable tolerance.