Summary

00:00 - Spencer has also asked, with long running race engines do we go for looser or tighter tolerances? OK so in terms of endurance race engines, let's talk about the tolerances for a start with our bearings.
00:14 So really this isn't a case of how the engine is going to be used or how long it's going to be used for.
00:20 This is more to do with how much power are we producing and what sort of rev range are we using compared to the factory and what the factory intended.
00:28 So generally the rule of thumb here is that as we move further away from the factory specifications for a given engine, so as we make more power we'd rev the car harder, the engine harder, we tend to build the engine with looser bearing clearances.
00:42 And the reason for this is that all of our engine components, our crankshaft and our engine block, our conrods et cetera, are all going to flex a little bit in use.
00:51 And obviously as our RPM and our power rise, the components flex more.
00:56 And we allow a little bit of additional clearance to just make sure that we don't end up with metal to metal contact as these components start to move around.
01:04 And we do couple this normally with a heavier weight engine oil as well, so we've got that cushioning protection from the engine oil to protect us from metal to metal contact.
01:14 In terms of our piston ring end gaps, because that's a topic we've talked about today, this is one area where with an endurance race engine we will generally build a little bit of additional clearance into our piston ring end gaps, and the reason for this is that that engine is going to be beat up on very very hard, lap after lap for potentially hours on end.
01:35 So the rings are physically just subjected to more combustion chamber heat for longer and hence they're likely to expand a little bit more.
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