best carberator for the stock slant 6
the same quality of fuel does the guy doing the the engine rebuild typically bore out the heads for larger pistons to compensate for poorer fuel or does he keep it the same as it was back in the day?
Unleaded fuel is not poorer quality. You can still get high octane ratings, at a price. Most people bore out a block to fix wear, not for more power, but it is much more expensive than a hone, re-ring, and re-use existing pistons.
Unleaded fuel turned out to not be as disastrous to older engines as originally thought. The problem is that the exhaust valves wear into the head faster since the lead oxide provided a cushion. For moderate driving and factory springs, that is probably a 100K mi wear concern. How do you know? If the compression is good, your engine is good. At that point, you might install larger exhaust valves to get to new metal. You can also have special hardened valve seats installed. I had that done on my 383 in 2001 and for only ~$15 per cylinder. Actually, I had it done earlier but the machine shop said they used regular seats, not hardened steel (can't trust many shops).
Newer engines arent' immune. Chrysler botched the Magnum design by induction hardening the cast iron around the exhaust seats. That worked for valve recession, but the heads are prone to crack between intake and exhaust, which is worse and made many boat anchors. All aluminum heads (most cars since 1985) surely have hardened steel valve seats, but the heads are prone to warp at the slightest overheat. Still, the weight savings is nice.
