Iron caps is defenitly no. Steel caps yes.
I suspect some engines have alloy caps too.
I have heard of preheating blocks to bore maintunnels though to me torque plate honing the cylinders warm would be more important. And very hard as well.
I own a V8 petrol Landcruiser [alloy block] which rattles badly when cold. But quietens down within about 45 sec. It does sound like an engine with a broken piston skirt. And having experienced many of them a bit scarey.
All engines I have ever built were production blocks and caps of several brands.
Alloy sprintcar blocks use steel caps. As do most iron ones as well. And to my knowledge are align honed the same on the same machine.
I have used synthetic oil for near 30 years. And have built engines with bit less clearance on the crank. 1.8 to 2 thou and have not had a bearing problem. But would if using a premium 25-50 mineral oil. Those were 2.5-3 thou. And still marked up bearings. Using synthetic means more power as the pump does not work quite as hard, which in turn puts less heat in the oil. And less oil pump drive gear/ belt wear as well.
As for road car engines having more oil clearance? Sorry. A racing engine of any sort has a lot more clearance than factory tolerances. See above. Factory is generally around 1.5 thou and sometimes less. Though with these modern turbo and s/c engines I suspect that is opened up a bit.
Edited by Lee Nicolle, 12 September 2020 - 08:58.