Can 327 blocks be overbored to 0.060"? I seem to recall back in the day that a motor with a "good casting" could be taken out that far (insinuating, of course, that a block with a "bad casting" could not). Does the technology exist today to be able to tell what a block might have left in it before actually boring it out and possibly ruining it worse than it is? My '66 motor is tired and I know that it was bored out 0.040" over back in the late 70's.

Thank you.

 

Yes, a good machine shop can test to make sure that there's enough meat left to safely bore it .060. If it's determined that .060 is unwise, the offending cylinder(s) can be sleaved if the block is worth saving otherwise (matching numbers, etc.). Most 327's are good for .060 but you won't know for sure until it's checked (or do you have a problem).

 

Is there any truth to having overheating problems when bored that big???

 

Yes, that's one of the reasons why the block should be checked first to make sure there's enough material for the overbore. If the walls wind up too thin an excessive amount of combustion heat gets transfered into the coolant, rasing temps (and costing power). I think the problem exists in a small percentage of blocks but finding out after a rebuild that the block needs to be replaced would be a major bummer.

 

VetteRodder, thanks for the information. It is nice to know that the old motor still might have a fighting chance (numbers matching original engine from my 66). Do you know the name of the process or the machine that is used to determine the remaining wall thickness? I'd like to know what I'm looking for if I decide to shop around for machine shops up here. Thanks!

 

I think it's called "sonic testing".

 

Not with salt and pepper but by the tempurature cycles from normal use. The seasoned blocks have relieved most of the internal stresses cast into it and are done changing dimensions/machined surfaces. Professional engine builders now super cool then oven heat and then vibrate brand new parts to season them but thats another story in itself. But before the 90's the used boneyard blocks were best. So what i'm saying is that what u call tired is really a great seasoned block.
I read that most pre-'70 blocks had more metal in the cyls and could easily handle the 0.060" overbore - but i can't seem to find that old reference. 0.060" overbore was fairly common years ago for high use applications - commercial cars, trucks, taxis. And there's nothing wrong with cyl sleeves - other than 'bout $200 @ sleeve - as some racers sleeve all thier bores/blocks (and then fill/partial fill the water jacket - yes another story). Yes [I]sonic testing[/I] is what they call it. A guy years ago claimed he bored his 327" out by 0.125" (1/8") and i heard this engine run but can't vouch for the piston size as i never actualy saw the bore size. Yet another vette collector claimed/bragged to me his 327" stingray was bored to 360" which would be more than 0.125" over (but could be just a 0.060" over 350" too). But It sounds like u may have original/numbers matching block which would increase ur '66 car value. It's obvious that u didn't buy a '66 to change blocks/numbers.
So keep that good o'l iron and fill it will all the performance goodies u want too but won't even be seen. Stroker crank, bore & big pistons, big cam, port the heads and intake too. Hey those ram exh manifolds can be reworked too - Brzezinski Racing (http://www.castheads.com/index.html). Ok ok i'll shut up now. But hope this helps. cardo0