No it's not !!!! don't speak unless you've tried it and failed...my 66 is .040 and it runs at 195 all day long with a stock radiator and no shroud..still has the original factory 4 blade fan set up.....now .060 would be pushin' it......040 will be fine and keep it original a gt will carry it's value more that way ftw!!!!

 

.040 is pushing it because of the core shift issue. There are blocks out there that will run ok at .040, and there are blocks that won't. Just because you're having good luck with it doesn't mean everyone will. As easy as it is to find 302 and roller 5.0 blocks, I don't see it as worth the risk unless you really, really want to keep your original block.

 

Go ahead and put in a modern 302 roller. Just make sure you set aside your original parts so if you ever decide to sell it, it can be put right back in or can be sold with the car. That way you don't have to worry about hurting your value or hurting the original parts.

 

give it up man!!!I speak from experience and real world examples...do you have a .040 302..??? have you ever used one for an extended period of time??? I have and I have one in the 66 in my sig and it's street strip and this isn't the first .040 motor I've had, I've built more 289/302's then you've ever looked at and more @ .040 then you'd know what to do with.......To many of you guys post on here theroy and what's read in a magazine instead of real world experience which often defies theroy.......I know the theroy you speak of quite well and have done plenty of machine work before.....and any machinist will tell you........yea yea yea it'll be fine and it is.....so nuff said.......I'm not trying to change your school of thought cause obviously that won't change.........but that line of thinking is right inline with the ole "go 331 and not 347 cause it'll burn oil and not be reliable and the rod ratios on a 347 are horrible vs a 331"....... I've got plenty of friends with 347 and no oil burn or destruction.......I have plenty more analogies about the ole 302 but one example will suffice...pull out a feeler gauge and add up .030 and then get a seperate .010 and see how little diff there will be by adding .010[&:] .anyway good day!!!

 

.040 over should be fine unless the block has excessive wear.
An alternative would be to get a different date-correct 289 block that hasn't already been bored.
I had to do that after the retards at the engine shop ruined my original 289 block!
I found a rebuildable '66 casting 289 block for $100 and had it bored .030 over. (By a different engine shop!)

 

if it is a K code gt with the 289 hipo and 4 bolt mains it might be kinda tough to find a correct date code block

my 289 is bored .060 over and the guy at the machine shop said it would be fine, and he knows what he is talking about, considering he has built more engines then most of you will ever dream of

 

Not that Ithink 0.040 over would be too much, but if the bores are good enough, why not just hone it. I have doneengines in the past that all they needed was a hone job. A good shop should be able to inspect and tell you if it would be good with just a hone job, or if it needs to be bored again. That would leave you at leastone more re-build on that block. My personal opinion is I wouldn't bore it if it didn't need it, but wouldn't be afraid to go to 0.040.

 

thats what i said earlier. ill ask roger at work. hes our machineist. im probably just wasting my time on here. i should be talking to my boss about it. since i work at daves engine and machine. (www.moparengineswest.com) but i dont go to work till monday so i thought id give the forums a try first.

 

When I rebuilt mine it was already at .040, just had it honed out to clean it up a bit and I'm running around .004-.0045 piston clearance, forged slugs though, so they expand and take up the room. Even in freexing cold startup there's no slap either.

And yeah, 347's don't burn oil....but the rod ratio does suck [8D]

 

4-bolt mains? Going on memory (I don't have a K-code), I'm pretty certain that the K-code used the same block as theC & A-codes did and does not have 4-bolt mains.

Jeff