BEARING CLEARANCE - How to MEASURE and PREVENT engine damage
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Published 2021-03-21
50mm-160mm 0.01mm Dial Bore Gauge bit.ly/36jYWQI
Dial Bore Gauge kit smaller diameters ban.ggood.vip/WVoz
How to zero micrometers and dial bore gauges: • DIY CYLINDER BORE CHECK: How to measu...
What is up engine heads! Today we-re talking about bearing clearances, we will explain what they are, why they're important and how to measure them.
When we speak about bearing clearance on an engine we're usually referring to the clearance between the crankshaft rod journal and the rod bearing as well as the clearance between the crankshaft main journal and the main bearing. You probably know that the key parts of your rotating assembly are never supposed to make contact with each other. Instead there's a film of oil between your crankshaft journals and your rod and main bearings. The bearing clearance determines the thickness of the oil film and thus plays a key part in your oil pressure and oil temperatures. If the clearance is too tight, metal to metal contact can occur under loads and during crankshaft flexing which in most cases results in damage and engine failure. Clearances that are too loose will make it difficult for your oil pump to maintain desired oil pressure and will also result in too much oil coming out from the sides of the bearings which will increase crankcase windage.
The right clearance depends a lot on the type of engine and its modifications and there is no one size fits all formula. However, There is a rule of thumb and it's this – 0.001 times journal diameter, doesn't matter if it's inches or millimetres.
Our engine right here is a second generation Toyota 4AFE 16 valve engine with 48mm main journals and 40 milimeter rod journals.
This means that our main bearing clearance is 48 x 0.001 which equals 0.048mm
And our rod bearing clearance is 40 x 0.001 which equals 0.040mm.
Now let's proceed to measure our bearing clearance. But before we do that we will do quick visual inspection of our crankshaft journals and bearing surfaces. Here we have two used Toyota 4A crankshafts, one which is in good condition and another which is in horrible condition. You can probably tell which is which. Obviously this crankshaft fails visual inspection, it actually spun two rod bearings and as you can see it has very noticeable deep scoring on the rod journals. The same logic applies to the bearing surfaces. Smooth and shiny like this passes visual inspection. Deep scratches and embedded particles fail visual inspection.
No we can start our measuring. To do this we will need two tools – a micrometer and a dial bore gauge. In order to measure things accurately we need to zero our tools. To make measuring easier we can set the crank on four main caps and apply a bit of oil to make turning the crankshaft easier. We are going to start by measuring our rod journals. We do this by gently moving the micrometer across the journal while we tighten down the small knob at the same time. The small knob or ratchet ensures that consistent and equal pressure is applied which results in consistent, accurate and repeatable measurements. The goal is simply to make contact with the journal. The micrometer should still be able to slide on and off the journal with a bit of effort. You will feel a bit of resistance but it will be low.
When it comes to the main journals we will do the same thing as with the rod journals. Measure at both journal halves and then perpendicular to these two locations. Now that we have our journal dimensions we can go ahead and measure our main and rod bearing bores. Once we have zeroed our gauge we will measure at six different locations. We measure by moving the bore gauge gently back and forth and observing the furthest point reached by the needle. The first and most important location is a vertical measurement perpendicular to the bearing parting line.
Now we can proceed to measure our rod bearing bore. Of course we do this with the rod caps torqued down to spec and we measure at the same spots as with the main bearings. Just like with the main bearings we don't measure at or near the parting lines or at or near oiling holes. Instead we measure perpendicular to the parting lines and at around 45 degrees from the vertical axis.
To get our bearing clearance we will deduct our vertical axis bearing bore measurement from our largest journal measurement. The result represents our rod and main bearing clearance.
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All Comments (21)
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0-150MM 0.01mm/0.0004 Inch Outside Micrometer set ban.ggood.vip/WVod%E2%80%8B 50mm-160mm 0.01mm Dial Bore Gauge bit.ly/36jYWQI%E2%80%8B Dial Bore Gauge kit smaller diameters ban.ggood.vip/WVoz%E2%80%8B Support d4a: driving-4-answers-shop.fourthwall.com/
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I love how this guy shares not only knowledge, but know-how also
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I also use platicgauge for checking bearing clearance. It may be old school, but its quick and simple,accurate and it works.
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My favorite part of Sunday mornings is hot coffee and new D4A! Best automotive channel on the interweb! Thank you so much for all your amazingly thorough and easy to understand videos!
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I'm an automotive engineering student and I didn't even know anything about oil clearance thanks for all the educational content. Your channel is awesome m8 :)
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I don’t even have a car but I NEED TO KNOW THIS!!!😂
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Finally finished the install on my turbo upgrade on my MR2T today! Feels so great to be finally finished (exactly in time for spring and my birthday next week)! Had to share with someone who understands.
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As the owner of a very old diesel engine I happen to live on top of (in a boat), you're an absolute godsend. Thank you so much for this!
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Thanks so much for this. I am a vibration analyst and all your videos on Recip. Engines are joy to me. I appreciate.
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Hey just a quick tip, i learned from my grandfather how to use the brown wrapping paper used to prevent rust on automotive parts, this paper cut into strips can be placed behind bearings to ajust the bearing clearance to a better smaller value without having to buy new bearings ..also may need to pass a file on the bearing parting surfaces to create a clearance when tightening the bearing caps...just avoid getting this paper wihin 0.5cm of the bearing lock tabs which are supposed to prevent the bearing from spinning in the bore...
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I finally realized my mistake in zeroing the dial bore gauge in the micrometer. I moved front part of it up and down not the spring loaded back part to zero it. I never knew whether i should push it in completely or if i should take any point in the middle and zero that. Now i found out that i have to do it the other way around. I don't know if somebody understands what i mean but you definetely made my day👍🏻
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Very good information. This is the only way to check for taper and out of round. And also for ordering the right size bearing, to make sure you have the right oil clearance
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I just love this videos its allways a perfect sunday when they come. When I meassure the clearence i use plastigauge.
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Best automotive maintenance Chanel!! Keep going!
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Absolutely TOP car channel!!. Love Scotty's, but not even close as clearly didactic & accurate as your 'in - depth' info!!.. Many thanks & Blessings!!.. 🤗🙏🙏🙏🙏
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I use micrometers just like that one everyday at work. This is a really good video as usual, but I'm a bit a skeptical of the sliding the micrometer method. Also, using these tools is a matter of developing a lot of tactile sensitivity. If people want to try this as amateurs it is great, but it takes quite a while to learn to use these tools precisely, and in the beginning it is hard to know if you are doing it right if you don't have other people around to compare your results with
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Thank you so much for this video. I never undestood very well the measures of the crankshaft before watching this video.
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Damn I just spun my rod bearing last week too. I was so lost on how to fix this and was considering just getting a new motor from the junkyard but now I might try to fix it. This video is totally kick ass man thanks a million you have no idea!!! Always look for your new videos
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Plastigage. Extremely accurate regardless of claims to the contrary. AND it measures actual torqued clearance which micrometers do not. Divide by 2 to get the actual oil clearance. Cost $3.
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I'm sorry for that retention algorithm, I clicked out of one of your other videos for this one
