Currently my car is at about 230ish whp. Im building up an engine to beable to run a few more psi and have a solid reliable 260ish whp. The car will see autocross and possibly a track day in the future.

ive seen mention of people runing .0020 oil clearance on both mains and rods which is past standard spec but only half of the .004 max spec. Is that something thats for a race engine only ? Id like to get 50k miles atleast out of this engine. Im not worried about oil pressure i have a BE Stage2+ pump ill be using.

is .0020 too much for a car that wont see alot of track time ? What do you guys suggest ?

 

I used standard clearance bearings.

 

I think the idea is that with the extra heat generated at the track, expansion doesn't close your .001-.0015 gap to next to nothing, potentially starving your bearings of oil. That being said, I've built a number of engines at .0015, with no issues. Don't have any 260hp track cars running around with my engines though.

 

what do you do to get to that clearance assuming tge crank is in spec ? My plan was to order two sets of ACL race bearings. One standard size and the other size that gives you .001 more clearance then mix bearing halves to get to around .015 oil clearance

 

It does not work like that.

 

mixing bearing halves is common. It does work like that

 

I've definitely heard of mixing bearings like that as well. Is it not a good practice?

 

I've got a year (perhaps 3K miles overall) of abusive street and time attack/fast autox driving on my engine. My clearances were in the 0.018-0.20 range. Car makes 302whp/292wtq SAE corrected. No problems so far.

 

Anyone elwe care to chime in ?

 

You would end up with one radius that does not fit the crank. It would be a tiny amount, but it would not be sitting wholly on the crank.

Who build engines like this? Have I missed something?

EDIT: I have been informed by multiple sources that this is in fact, common practice. I never knew that.

 

They're not matched in the packaging, just thrown in there. Once they're run into the crank, no, you can't mix and match. Did that once, locked the crank. Or is that what we're talking about?

 

I think, I thought we were talking about mixing. 001 and .002 bearings.

 

It works because the bearing doesn't have a consistent oil clearance. They're slightly egg-shaped with tighter clearances top/bottom and wider side/side.

 

I know you have built many track motors. What clearances do you recommend for the use i described in my first post ?

 

Send him $4099 and he'll tell you

 

I bet 98% of people run Standard clearance. the 2% being experimenters and short lived track engines. You have had a handful of people tell you standard is fine, running a lot more power than you intend. Its okay, I was super neurotic when building my engine too. your fine, move on.

 

You betcha

e:

 

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Not trying to help you dig more but why would you say that? Guys got a business building engines. If he doesn't build engines he doesn't eat so to speak. Tricks a builder uses sets them apart from other builders. The better ones stay in business the rest don't.

 

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