Crankshaft measurements

[Odmark91]

Hello! Im going to put together a 426 and took some measurements of the crankshaft today since the bearings arent marked with anything.

I used a newly calibrated micrometer, and this is what i came up with, this is the average of many measurements.

Main journals, (1 being closest to front of engine):

1 : 2.754"

2: 2.753"

3: 2.754"

4: 2.754"

5: 2.753"

Rod Journals, (1 being closest to front of engine):

1: 2.334"

2: 2.333"

3: 2.332"

4: 2.332"

I dont know if im just confused right now, but wouldnt this mean that the rod journals are like 0.040 undersize and the mains are just a little bit oversized? I measured everything multiple times because i just couldnt make sense of it. I guess the mains could probably be uncut and i messed up measuring just a little bit, but the rods? Does 0.040 bearings even exist?

 

[Outsider]

Wow, more questions than answers. Used crank that came with a complete engine, or the crank was picked up separate as an unknown condition item? If it's an old fueler crank, it's probably cracked junk.

Big journals usually is from welding or chroming prior to finish grinding, and 0.040 undersize, particularly with the wide variance you measured is a perhaps a pre-grind for welding or chroming. In any case it doesn't sound like you a have a usable crank in this form. Probably safest to buy a new crank, but if you choose to use, mag it before you spend any more money on it.

As for bearings, yes despite your numbers that look outside the useful range, they do make 0.040 bearings. Though I don't think they are readily available and I believe they are only made every few years in small quantities.

 

[Odmark91]

The crank was in the engine that originally sat in my car. It ran really good but when i pulled it and installed the 505 stroker engine i dissasembled it and the bearings looked a bit worn. Now i have polished the crank and it looks fine, so i was going to get new bearings and just slam it together. But these measurements just doesent make sense to me. I need to go out and do it again.

 

[Outsider]

You have a mic standard like in the pic below? Do you use mics often? Is the crank really clean, almost more concerned the "big" mains. But in any case use to seeing variations in .0001s, not .001s.

 

[toolmanmike]

Hello! Im going to put together a 426 and took some measurements of the crankshaft today since the bearings arent marked with anything.

I used a newly calibrated micrometer, and this is what i came up with, this is the average of many measurements.

Main journals, (1 being closest to front of engine):

1 : 2.754"

2: 2.753"

3: 2.754"

4: 2.754"

5: 2.753"

Rod Journals, (1 being closest to front of engine):

1: 2.334"

2: 2.333"

3: 2.332"

4: 2.332"

I dont know if im just confused right now, but wouldnt this mean that the rod journals are like 0.040 undersize and the mains are just a little bit oversized? I measured everything multiple times because i just couldnt make sense of it. I guess the mains could probably be uncut and i messed up measuring just a little bit, but the rods? Does 0.040 bearings even exist?

Yes the rod bearing journals are smaller than the mains.

 

[Odmark91]

Outsider: Yes i used a mic like that, and no im quite inexperienced with these. The crank is very clean, i tried measuring agian but came up with the same numbers. Tried my digital caliper just for a baseline but with that i got numbers around 2.354" for the rod journals, wich makes more sense.

I actually found out that ONE(!) of each bearing, main and rod, was stamped with 020 for the rods and 010 for the mains.

 

[Outsider]

Hmm.... there is technique to using a mic. Sort of a small sweeping and rocking motion, and if you don't use frequently, use the mic's clutch.

 

[Odmark91]

Hmm.... there is technique to using a mic. Sort of a small sweeping and rocking motion, and if you don't use frequently, use the mic's clutch.

Maybe i should watch some videos on how to do it correctly and then do it again. Ill get back to you!

 

[padam]

Probably reading the mic 1 turn off (.025)

 

[Cranky]

Also I like to mic the journals in more than 1 place to check for taper and roundness and also, I've found that everyone has their own 'touch' for measuring. Even machinists that's been doing it for years and years seem to come up with differences. And measure 'each' rod journal....1 through 8. With the differences you're getting and if your touch is right, they should be the ame 1-2 and so on. Seeing .002" difference shouldn't be happening. Posting a pic of the crank and your mic might help?

 

[Fran Blacker]

Have you stood the crank up on something solid and give a counter a good tap with a hammer? You don't have to kill it. If it rings probably doesn't have cracks. I if goes thud not good.