Nice presentation! Thank you!

AG I’m glad that you’re bringing attention to the most important part of the engine build. Bearing clearances are one of the “make it or break it” aspects in engine building. That and getting the block and all parts that go in it as clean as humanly possible!

Good job Alan. Nice presentation. Definitely useful. I didn't continue down my early mechanic apprenticeship path. Your channel really inspires me and makes me wonder what if. There is always a tidbit of new information that you release. I really appreciate you and your crew's efforts. Keep em rolling.

Very well done Alan Excellent!

Good stuff Alan

Back in the early 80s my highschool mechanics teacher was telling the class that the oil off of our fingers would cause a premature bearing wear. I never did become a mechanic but I sure did spin lots of small block Chevy bearings. Over revving stuck in the mud. I would buy bearings from Canadian Tire and change them out with the motor still in the truck.

Love your videos AG, very informative 👍

If you inspect the back side of original factory bearings, you'll occasionally come across ones that are marked .0006 U/S, presumably to deal with bottom spec crank journals. It was quite common for us when rebuilding a stock 350 with a factory cast crank to just polish and use .001" U/S bearings as they typically measured bottom size or very close to.

I spun a main on a "balanced and blueprinted" big block I built, that was an expensive lesson. I did not check the machine shops measurements since they had done ALL the machining and balancing. They claimed it was my assembly, but it's the only time it's ever happened. I assumed.

I believe the factory used air gauges on the crank, very fast to do to get size, Callie's use this on theirs cranks and rods, I saw this on a tour a few years ago, can even use air gauges on bore sizing, good video, always check the back of the bearings on a factory block, if upper and lower are different size, you will have to align hone the bore,I haven't seen this on rods only on mains,on a race engine all the bearing clearance should be the same front to back to even the load, if more clearance on 5,4 will take the load, good video, gets me thinking!!

Great info!!

New aluminum blocks also expand more when they get hot. So the clearances on aluminum and iron are different too

Had a shop assemble a short block 355 and had one bearing full copper and the rest 10-50% copper showing. Had 60 psi oil pressure and about 40 warmed up. Second time the same crank and block crank wiped bearings. Both assembled short blocks two different shops.

Yes that is helpful. I ran into the same thing with a LT1 right back from the machine shop. 1 rod bearing gave way to much drag on rotation as I was assembling it. I caught it and it was resolved. It could have been a nightmare though.

This is also another advantage of using a lightweight crankshaft it’s easier on bearings. The engine I’m building is getting a 43 pound crankshaft instead of the stock 54 pound one. Plus the free horsepower gained and quicker revs from not spinning all that extra weight.

Always... always... always... when regrinding any Crankshaft.... even stock stuff for even modest HP applications.... target "lowside" or small sizing of the journal tolerance, to allow yourself "ROOM" ..... so that when ReSizing the Connecting Rods or Line Honing the Mains to can "set" the Vertical Oil Clearance where you want it for the target application. (Think the 'Tonawanda' hp engine plant) Then all you have to do when Line Honing/Rid ReSizing is stop prior to the Bore tolerance and "checK' with your dial bore gauge prior to final sizing so you know 'where' you are clearance-wise..... and having already put the "room" for Oil clearance ON THE CRANK... you can then final size Rods/Mains and provide good Bearing Crush as well ! Example: If you want tighter closer to .002" Rod Brg Clearance ? after stopping/checking... you can merely final size the Rod right at 2.2247" or even a coupla 10ths under for good crush if you want more Rod Brg clrc ? say to .0025" ? after stopping/checking.... then you can continue final sizing the Rod Big End closer to 2.2252" which is the high end of tolerance but still good crush. NEVER take a Rod Big End higher/above/looser above tolerance. Again here: think 'Tonawanda' plant wherer ALL Crank were ground 'lowside' for this reason ! I don't let anyone "Machine" a 500 hp resto deal nor an 970 hp N/A SS Drag Engine I'm assembling.... unless they are under my direct supervision? or I'm doing it myself ! And that's why most HotRod Callies/Billet Cranks are/were supplied .0005" BELOW tolerance for the aforementioned reasons.

I ordered some Mahle/Clevite .001 under the other day in the A series it took 3 warehouses to get a full set. The first 5 that come together were marked correct on the bearings but when I put the ball Mic on them they were standard size. Then 2 others come in and then the final set. They were marked correct and measured correctly. 3 years manufacture dates and of course 3 lot numbers. I sent them all back and said I want all the same lot numbers. I also ordered 2 other sets from other vendors. 🤔🙄🤕🤦‍♂️🤷‍♂️ I have been at this long enough to remember feathered shims. Also removing shims to correct clearance. 😁😎

We went through a camry engine back in the late 90s and while its been to long for me to remember I think they had specific numbers for bores and bearings where they graded them. Maybe they used air gauges or something that resulted in tighter tolerances as i remember the toyota guy that ran our route said toyota got their tolerances down to a specific micron size, which was odd for me hearing microns when dealing with clearances.

Thank you for another great show!! Would this level of detail be described as blueprinting an engine??

I believe the letters stamped along the pan rail denoted which standard/oversized/undersized bearings to use for the rods on the assembly line..

Is machinist I built so many small block Chevys I have lost count. Never had no problems. I did catch a set of timing gears that I almost put on, that were marked one turn off gear was still good I just remarked it.

I've been messing with a couple of relatively modern motorcycle engines lately and in production they use selective assembly with part clearances worked out on the fly by picking between bins, cranks are numbered or lettered and rods the same, bearings are color coded. A mix of humans and robots. It all goes together and lasts a very long time as long as maintenance schedules are followed. It is not unusual for motorcycle engines to easily exceed 100,000 miles with nothing, but fluids and valve clearances set, quite a change from my youth.

Yup! Just built a smallblock chev and spun 3 mains. Oil pump pickup fell off! Not clearances issue here.

Pretty sure I read decades ago, that the Tonowanda engine plant built the engines with closer tolerences.

You always check the machine shops clearance. They make mistakes too!

the information in this video is only partially correct! Your Canadian backyard engineering left out two other very important measurements that also affect bearing clearance!!!! The main bore diameter and the rod bore measurements also contribute to stacked bearing clearances or lack of clearance Both of those measurements can be manipulated within their tolerance range to adjust bearing clearance. They can only be manipulated by a machinist not a backyard hack like yourself!!!!