SBC Crankshaft main journel sizes

[cncguy987]

Just curious what are the dimensions called out for the main and rod journals on a 2.45 main crankshaft. There are a few similiar numbers mentioned on the internet but hoping someone had a print to confirm the numbers. Thanks.

[modok]

The shaft size is determined by the bearings.
Unless you will be having bearings made to fit the shaft.

The shaft sizes listed in the bearing catalog are usually exactly the same as provided to the bearing company by the manufacturer.
Or pirated by the bearing company...... and they do sometimes change.

As the famous case of the extra clearance on #5, was sometimes provided by a thinner bearing, or other times provided by a smaller shaft size, which has caused some confusion.

I feel as if we have discussed this before, but I may be wrong.

[cncguy987]

You may have discussed this before, but that wasnt the question. I was asking for the dimensions on a sbc print. If you werw going to machine a crankshaft, you would not look at the numbers on the other side of the bearing.

[cncguy987]

You gave me an idea and went and looked at some acl prints. Their od or housing size is close to the numbers on an oem cylinder block print but not the same. Another reason im more curious about the numbers.

[Dave Koehler]

https://www.mahle-aftermarket.com/na/en ... alog-pdfs/

[cncguy987]

Thanks Dave

[modok]

You may have discussed this before, but that wasnt the question. I was asking for the dimensions on a sbc print. If you werw going to machine a crankshaft, you would not look at the numbers on the other side of the bearing.

Yes I would.
I remember now, it was seals.
Bearings, seals, all the same rule. It is best to make the shaft the right size for currently existing seals and bearings, not the other way around.

At the production level, there are often several size categories, for selective assembly, but that was then and this is now.
No sense looking for the bearings that were used 40 years ago, you might want to also look for antique cans of motor oil to go with that.

[Dave Koehler]

Modak,
I think you over explained it. He was looking for crankshaft dimensions not clearance considerations.
At least that is the way I read it.

[modok]

Yeah I don't know.. maybe.
Who makes these blueprints he is always looking for?

He can do it himself if he knows where the dimensions come from.

[engineguyBill]

When an engine is originally designed by OEM manufacturer's engineering staff, they draw prints of the crankshaft as well as the cylinder block. They send these prints to the bearing manufacturers, along with related nomenclature such as vertical oil clearance, thrust surface design, etc., etc. The bearing manufacturer then draws prints of the bearings for this engine and submits the info back to the OEM. The bearing manufacturer also makes recommendations concerning bearing materials, eccentricity, crush, etc., etc. Once all of this information is sorted out, the bearing manufacturer submits a quote for the bearings in question.
Not sure if this is the subject of this post, but everything is relative to the original crankshaft and cylinder block prints provided by the engine manufacturer. The information that you will find in various engine bearing manufacturer''s catalogs, regarding journal diameters, housing bore size, shell lengths, etc., is very accurate information and can be trusted as such.

[cncguy987]

Thanks Bill, i think i agree with those thoughts and will work my crankshaft demensions and tolerances around the bearing specs listed on clevite's website. Worst case im out of a 150 dollars of bar stock.

[bigmike]

The dimensions called out for the main and rod journals on a say 2.45 main 350 crankshaft by chevy changed slightly over the years and it can also depend on if the 350 engine was being used in an auto or manual car or 307 . But generally for Rod journel 2.0990 - 2.1000.

#1 main 2.4484 - 2.4493
#2,3,4 main 2.4481 - 2.4490
#5 main 2.4479 - 2.4488

[Dave Koehler]

Thanks Bill, i think i agree with those thoughts and will work my crankshaft demensions and tolerances around the bearing specs listed on clevite's website. Worst case im out of a 150 dollars of bar stock.

We want photos and videos as you go on your journey, good and bad.

I would like to try carving one out someday but I figured I would have more in it than I could buy one for. Not to mention the learning curve.
"Wait, you don't just select from column A and push a button?"

[cncguy987]

Sure i can take some pictures or videos of the processes. With this covid thing going on, i unfortunately have more free time to finish up this project. I probably have have 100 hours into the crank and 500 plus hours into the block.