The Ford Barn - View Single Post - Sonic tests back-Too thin for 3 5/16 ?

Bored&Stroked · 05-25-2022, 03:10 PM

The smallest number appears to be on a cylinder that is .188 or so on the other side, so they can move the bore over .020 and center it. Given the measurements, I don't see an issue with a 3.3125 bore.

Couple Points:

1) I don't like to do sonic testing on just one location of the bore (top to bottom). I prefer to sonic test each cylinder on all 4 sides, at 3 different depths in the bore. This helps me see if the readings are consistent up and down the cylinder - the 12 readings give me that.

2) The areas that you need to care the most about are the major piston thrust sides of the cylinder. Given the crank turns clockwise, then the major thrust on the driver's side is toward the intake ports, while on the passenger's side it is closest to the outside of the block.

One caveat, sonic testing won't identify a rust pit or other casting issue in one particular spot. There is really no easy way to know that you might have an issue . . . though you can pressure test the block after boring to make sure there isn't an issue. I always try to look into the water jackets and see how much rust and scale I see. If it appears to have a lot of rust issues in its lifetime, then you may want to be a bit more conservative on the bore.

05-25-2022, 03:10 PM	#12
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,068	Re: Sonic tests back-Too thin for 3 5/16 ? The smallest number appears to be on a cylinder that is .188 or so on the other side, so they can move the bore over .020 and center it. Given the measurements, I don't see an issue with a 3.3125 bore. Couple Points: 1) I don't like to do sonic testing on just one location of the bore (top to bottom). I prefer to sonic test each cylinder on all 4 sides, at 3 different depths in the bore. This helps me see if the readings are consistent up and down the cylinder - the 12 readings give me that. 2) The areas that you need to care the most about are the major piston thrust sides of the cylinder. Given the crank turns clockwise, then the major thrust on the driver's side is toward the intake ports, while on the passenger's side it is closest to the outside of the block. One caveat, sonic testing won't identify a rust pit or other casting issue in one particular spot. There is really no easy way to know that you might have an issue . . . though you can pressure test the block after boring to make sure there isn't an issue. I always try to look into the water jackets and see how much rust and scale I see. If it appears to have a lot of rust issues in its lifetime, then you may want to be a bit more conservative on the bore.