What is the max safe bore amount for a 1965 327 small journal engine? I have a nice block that is at .040 and needs cleaned up, is going .060 too much? Machine shop telle me he wouldn't recommend it because potential overheating issues? True? It's a good clean block otherwise. Thoughts?
If it were mine...I'd think about how many miles it will get put on it, and how much taper it has in it now, or any other problems with the bore. If it only needs to last 30-40k miles, and the taper is .005" or less, I'd just give it a light hone and put new plain cast rings in it, and run it. But you can also get it sonic tested, and bore it to .060, or whatever else you want to spend money on.
for a 60 over motor, depends on the car the engine is going in and if it has enough radiator and airflow. I have a 60 over 350 currently in my 33 and it overheats pretty quick in traffic. Have had other 60 over motors in other cars and its hit and miss.
The machine shop is saying So you want ammo to argue with them? As said, sonic check the block. Here's one discussion on it. https://www.chevelles.com/threads/whats-correct-way-to-sonic-check-a-block-for.822985/ Then check for pistons. I'm wondering if you go custom if you could get something between the current .040 and .060, if it will clean up at less. Since both the machine shop and others here have mentioned that a thinner bore does run hot, expect to have a top grade cooling system, too.
As others say, check how thick the cylinder walls are, and go from there. (Even if there may be plenty of metal core shift during manufacturing may have caused the bore to be off center, making the walls thinner on one side.)
The Jalopy Journal
