Is there a "how to.." for crank measurement, and bearing verification? Options

[malcolm2]

I am gonna make a 2 liter from my 1.8. So I have a refreshed 71mm crank that I have been told has been ground to -0.010.

I measured as best as I can with a digital mic and got about 59.66 on the mains and 49.65 on the rod journals.

Where can I find the STD specs and ranges ? were they 60 and 50, respectively?

Since I know nothing about this crank, how can I verify the 71 mm measurement?

[malcolm2]

How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...

[Superhawk996]

How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...

Stroke of the crank 71mm is measured from the centerline of the main bearings to the centerline of the rod journal. That dimension should be 35.5mm or 1/2 the stroke.

It will be difficult to measure perfectly without putting the crank between centers, doing some set up of height gauges and some math to account for journal radius offset.

A 1.7L/1/8L is an offset of 33mm from crank centerline. A difference of 2.5mm to the 2.0l crank. That 2.5mm is 0.100” and could easily get lost in an eyeball or tape measure type measurement.

Easier way would be to mock up, and then measure the actual stroke of a piston. That should be 71mm.

[Mark Henry]

How about the 71mm measurement? Not that it matters, just curious if I could measure that.

THe rod journals are smaller, but otherwise it looks just like the 66mm from the 1.8. I thought the rod journals were smaller and offset. seems like 5mm offset would be visible.

Any other way to tell it's a 71mm? Markings, etc...

Stroke of the crank 71mm is measured from the centerline of the main bearings to the centerline of the rod journal. That dimension should be 35.5mm or 1/2 the stroke.

It will be difficult to measure perfectly without putting the crank between centers, doing some set up of height gauges and some math to account for journal radius offset.

A 1.7L/1/8L is an offset of 33mm from crank centerline. A difference of 2.5mm to the 2.0l crank. That 2.5mm is 0.100” and could easily get lost in an eyeball or tape measure type measurement.

Easier way would be to mock up, and then measure the actual stroke of a piston. That should be 71mm.

The T4 crank is a flat-plane crank, just use a vernier caliper and measure from the bottom of one throw to the top of the next throw. You can use a straight edge or just eyeball it. It will even work telling the difference between a 78mm and 80mm but it might be hard to tell between a 78mm vs a 78.8mm crankshaft.

It's not a dead accurate way, but quick and easy to identify if it's a stock 66mm or 71mm crank.