Lykins Motorsports How Do You Adjust Bearing Clearances???

Added: 2026-05-23

[00:00:05][clears throat] >> What's up, guys? This is Brent with Lakins Motorsports. I get a lot of inquiries and questions about um what I usually like to see as far as main and rod bearing clearances go and how to check those and how to adjust it if if it's not what you want.

[00:00:25]Um so, I thought I would take some time and and address some of those questions and uh I'll I'll throw some graphics up on the screen so that you can save it and um maybe help yourself when you're putting your own engine together.

[00:00:41]So, anytime that you go to put a crank in the block or put rods on the crank, you have to check your bearing clearances.

[00:00:50]If you don't have the correct clearance, you can wipe out an engine or you can have excessive clearance and um you know, have some oil bleeds or some hemorrhages where you don't want those to be.

[00:01:03]So, uh this is a critical point of engine building and you just can't slap that stuff together.

[00:01:11]Um some guys like to use plastic gauge, which is just basically it looks like dental floss, um but it's not accurate and and I wouldn't count on that to uh to set up a high-dollar engine.

[00:01:29]The correct way is to use a micrometer to measure the journal size that you're working with.

[00:01:39]Then, I like to put it in a mic stand and then you use a bore gauge.

[00:01:47]You zero the gauge to to that mic.

[00:01:51]And then, when you put the bore gauge in the bearing housing, whether it be a main bearing housing or a rod journal housing, it shows you the differential, which would be your bearing clearance.

[00:02:03]So, um you have um all kinds of different engines, and you know, the bearing clearances will change depending on the application, the engine family, the the the rod journal size. A lot of engines um you can run a factory rod size. So, like your your factory FE, factory Cleveland, factory Windsor, uh factory Ford 460, uh you can run a factory rod journal on a factory crank. Your aftermarket stroker cranks will usually use something like a small block Chevy or a big block Chevy rod journal. So, all that determines what bearing clearances you want.

[00:02:50]And if you're, you know, looking at bearing boxes or part numbers at, you know, at your favorite retailer, um you'll see all these different nomenclatures for bearing part numbers, and um little stuff suffixes, I guess you would call them, a suffix at the end of the part number.

[00:03:10]And uh so, maybe you know what those mean, maybe you don't know what those mean. So, um you know, whether it be um you know, a less expensive Scat small block Chevy rod, or a very expensive Oliver, you know, big block Chevy rod, um you know, all the uh procedures and everything will be exactly the same.

[00:03:37]All right, so, here is my rule of thumb for recommended bearing clearances. So, very easy, it's just 1/1000 of an inch per inch of crank journal. So, if we were to look at some examples, um your Ford FE, your your Ford Cleveland, your aftermarket Windsor stuff has a 2.750 main journal.

[00:04:03]And if we multiply that by 0.001, then you get somewhere around 0028.

[00:04:13]And and that would be usually about the minimum that I would run for for that size journal. So, you know, your recommended clearances would be, you know, somewhere around 28 to 3, 31.

[00:04:27]You know, uh a tenth or two isn't going to hurt anybody.

[00:04:34]But that would be the recommended clearance for, you know, something like a Ford Cleveland. On on the right side of that graphic there, you'll see a 2100 rod journal. So, that's a small block Chevrolet rod size.

[00:04:48]And again, if we do the 2.100, multiply that by 1000th per inch of journal, we get around 2000ths of a tenth. So, you know, I usually aim for around 2000ths to 2 and 1/2 thousandths for for a small block Chevy rod journal size. And again, you know, if that's a little bit on the fat side, you know, by a tenth or two, or you know, across eight rods, you have variations of, you know, two or three tenths, that's perfectly fine.

[00:05:24]I generally do not like to run under that 0020 number, unless you know, it's for a specific application and everything has been dialed in, you know, perfectly and the right oil viscosity and the the crank is perfectly round and and all that stuff.

[00:05:45]So, I just thought that I would throw uh another graphic up here and as as Ford guys, we usually deal with, you know, the same engines over and over and over. I build a ton of Ford FEs, Clevelands, and Windsors, 302s, uh the whole shooting match. So, these are the bearing clearances that um I usually aim for on a on a standard street or street strip engine bracket race motor or something like that. Um and the different engine family. So, if you just start with number one at the upper left-hand corner there, um a Ford FE with with standard factory Ford FE rod journal sizes, I usually aim for around um 0028 to three on the mains. Again, if you end up at, you know, 32, 33, it's perfectly fine. I've been there. Um you don't really know the difference.

[00:06:48]Um I just don't like to go on the low side. You know, there's there's a good saying, it's a famous saying, that if uh if your bearing clearances are too loose, nobody will know about it, but if they're too tight, everybody will know about it.

[00:07:03]Um on the rods, since a Ford FE factory rod journal is a 2. uh 438 size, um I'm generally at somewhere around two and a half thousandths to three thousandths.

[00:07:16]So, on the old factory rods, if you're using, you know, factory rods, um I like to aim on the loose side. Uh a lot of those rods will deflect and distort with stress, whereas your aftermarket rods, such as your Molnar rods, Scat, etc., um they're going to be a lot more rigid, a lot more stronger, and you can close up the clearances a little bit.

[00:07:44]Number two there, Ford FE with big block Chevrolet rod journal. So, um that is you know, your typical Ford FE build with a stroker crank from Scat.

[00:07:55]Um you know, a two and a eight I'm sorry, four and a eight or four and a quarter stroke. So, your typical you know, 445 FE.

[00:08:04]Again, the mains going to stay the same cuz the main journals are are the same size on the aftermarket cranks.

[00:08:11]Uh on the rods, they use big block Chevrolet rods.

[00:08:14]So, um you know, a big block Chevrolet rod journal is 2200.

[00:08:19]So, if we use our point uh or our 1,000th of clearance per inch of journal, you know, we'd start somewhere around that 22 0022 mark to 2 and 1/2 thousandths.

[00:08:31]Um and we can just roll through here.

[00:08:34]Uh number three is a 4302 based engine.

[00:08:36]They're very small on main journals and rod journals both. So, the clearances are are generally the same or you know, thereabouts the same.

[00:08:47]Um number four, the 351 Cleveland with a factory rod journal.

[00:08:52]Uh the the factory rod journal size for a Cleveland and and a Windsor are uh about the same.

[00:08:58]Just a little bit fatter than than a big block Chevrolet.

[00:09:02]But uh the mains, since it's a 2750 main just like an FE, you know, I'm somewhere around that 0028 uh 003 number.

[00:09:12]And um number five uh again, your aftermarket stroker cranks come with small block Chevrolet rods.

[00:09:21]So, uh smaller journal than the factory 351 Cleveland and 351 Windsor rods. So, the clearances will tighten up a little bit.

[00:09:30]Uh number six, 351 Windsor with a factory rod journals. The Windsor 351 Windsor has a big old fat main on it.

[00:09:38]It's a 3-in main.

[00:09:39]So, you need more clearance. Um I usually aim somewhere around 3,000 to 3 and 3 and 1/2 thousandths on on the mains.

[00:09:48]Um and and the rod journal size is uh 23 10 or 2311.

[00:09:55]And um rod size or or your bearing clearance would be somewhere around 0023 025.

[00:10:04]Um and then etc. etc. number seven 351 Windsor using an aftermarket crank with aftermarket small block Chevrolet rod journals. Number eight uh Ford 385 series again has a 3-in main. The rod journals are are fat. So, you have to adjust that clearance uh appropriately.

[00:10:27]And then number nine uh 385 series with a big block Chevrolet rod journal. So, adjust those clearances.

[00:10:35]And um as my note in the bottom left corner says, these clearances are um are recommended based off of, you know, basically 23 years of engine building experience. So, uh it's a good starting point. There will be a few specific uh applications where you can or you have to uh deviate a little bit from those, but for the most part, that's a good place to start.

[00:11:04]All right. So, um you're checking your clearances and they're not what you want them to be.

[00:11:12]How do you adjust that? Uh I get that question very often and um if you have something, okay, let's just take an example, say a Ford FE and uh on the mains we have about 2,000ths of of main bearing clearance.

[00:11:30]Um I like to run looser than that.

[00:11:34]Um, so how would you handle that? You would use what's called an X bearing.

[00:11:39]I'm looking at the number one up there at the top right hand of your screen.

[00:11:43]The X means extra.

[00:11:45]And it gives you 1,000th extra clearance. So, if I were to use um, in our in our example of the Ford FE um, and and our 2,000th main bearing clearance, if if I were to use an X bearing, then I would get closer to the 3,000th mark where I want to be. The caveat here is there are no X bearings for the Ford FE main journals or main bearings. So, you have kind of have to get creative.

[00:12:15]Um, we usually swap in Cleveland bearings since the journal size is the same.

[00:12:21]You just file the tangs off the bearings and slip those in. And then you can use a Cleveland bearing with with an X or whatever you uh, you need to use. It's very unfortunate that the FE doesn't have a lot of bearing selection like that.

[00:12:37]So, as of um, number one there, we can go to Oh, in the examples of the X bearings, I gave some examples. These are all Clevite part numbers. So, for your Cleveland, it's an MS 1010. And if uh, the H means a high performance bearing.

[00:12:56]Um, the X uh, is an extra clearance. So, that would be the nomenclature that you would see on the part box, like you I showed you at the very beginning of the video.

[00:13:08]Um, in in our number two point there, so you don't always have to um, use an X bearing.

[00:13:17]You can mix and match.

[00:13:19]So, if you were to mix and match a standard and an X bearing, you would get instead of 1,000th extra clearance, you get a half a thousandth of extra clearance. So, that would be that situation where you're building that Ford FE or that Ford Cleveland, you're at 2 and 1/2 thousandths on the main bearing clearance, and you want it closer to three, then you can mix a standard bearing and an X bearing, and and get that dialed in a little bit closer to where you want it.

[00:13:49]So, there's often times where depending on and I'm looking at number three here, there's often times depending on the crankshaft manufacturer, or like I told you earlier that the Ford FE does not have X bearings, and some guys don't want to take the time to grind the tangs off a Cleveland bearing, or they're scared to do that, um you can have the crank touch ground.

[00:14:15]So, what I usually do there is you have to find a reputable crank grinder who can do this. Not every crank grinder can.

[00:14:25]But, I usually take the measurements that of the journals, write those down, and show the clearances that I get with whatever bearing I want to use, and then just hand that to the crank grinder, and he can adjust the journals down to match. So, you can dial it in that way.

[00:14:43]Um so, number four there, just like um you're adding clearance, you can take it away. If you have a real sloppy bearing clearance, um the the bearing part numbers have a one on the end of those. So, as an example, um our Clevite small block Chevrolet rod bearing, so a CB663 HN, H means a high performance bearing, and N bearing is a narrowed bearing that you have to use on a lot of the stroker cranks. But, that one means it's going to be uh [snorts] 1,000th tighter clearance. So, if you throw a set of standard bearings in, and you have 3000s of clearance, you can use these uh bearings with the one on the end, and you can get it down closer to two, if that's what you so desire.

[00:15:32]And just like uh you can mix and match for more clearance, you can also mix and match for tighter clearance.

[00:15:38]So, all of that are uh you know, different tool tools in your toolbox that you can use to get the bearing clearances dialed in. So, um you know, you just want to recap, get yourself some good tools, um a decent outside mic, and a decent bore gauge won't cost you a million dollars, and you'll get lots of better results from from using those, and learning how to use those, than to just throw a piece of plastic gauge on there, and hope for the best.

[00:16:11]So, um feel free to look back through the video, and you can see, you know, if you're building a Ford engine at your home, um and you're not sure on what to do with the bearing clearances, you can look back, and uh reference this video, and and get those dialed in.

[00:16:30]Hope that helps you guys, and uh I'll see you later on with some more videos.