I have a 74 302 block that I just had reconditioned for the stang. The block had already been bored so the machine shop bored it 60 over. Should I be worried about this weakening my cylinder walls. I want to make sure this wont be a problem before I start buying a rebuild kit. I don't plan on supercharging the engine or anything like that. I just need to know if I need to look for a new block if this one is going to cause problems. Thanks in advance!
60 over bore
- Thread starter MattK67
- Start date
Was the block sonic checked prior to being bored? I know people who are running .060 without problems, I've even heard of people taking it up to .070 on race engines. A lot of people will tell you the safety limit for 302's is .040, but in my opinion, if you can address a couple of issues, you will be fine. 70's blocks are good quality, more so than 80's, I would want to know the thickness of the cylinder walls before I started dumping money in it, your machinest should have tested it before he bored out the cylinders. The main issue is cooling, since you will have thinner cylinders walls, heat dissipation becomes a problem. I would also be concerned with the type and quality of oil you are using. If you can take care of these issues, I see no problem.
SoCalCruising
Founding Member
The general limit in the 4.030-4.040 range is based on the non-uniform thickness of the cylinder walls that occurs from core shift and any other factors that affect the bore (like improper bore centering). A "perfect" block, and there will be some of these among the millions made, will have uniform cylinder walls that will permit a larger over-bore without achieving a too-thin wall thickness at one or more sections of the cylinder wall. This must be the case for all cylinders.
Like said above, if the block was sonic checked and deemed to have enough wall thickness, then you may be fine. Be aware, however, that thinner bores will distort more easily as the engine heats/cools and ring seal may not be as good as a new or 4.030 block. If your car is a "cruiser", it probably won't matter.
Like said above, if the block was sonic checked and deemed to have enough wall thickness, then you may be fine. Be aware, however, that thinner bores will distort more easily as the engine heats/cools and ring seal may not be as good as a new or 4.030 block. If your car is a "cruiser", it probably won't matter.
SoCalCruising
Founding Member
There are probably a lot of old blocks like that. But Ford has to take into consideration all of its blocks, even those far from the ideal. Glad yours was good.
