445 block question

The difference in piston size with the same number might be from looking at the number cast into the pistons of some manufacturer's. I think some of them had the same casting number but had either STD, .020, .040, or .060 stamped into the top of the piston.

I have a 4 Star (206 engine) that I had 2 engines, each had a broken sleeve in 1 block & 1 good block. They were different sizes (1 - .020 over & 1 .060 over). I put it together using the good blocks and their corresponding pistons about 20 years ago & have never had any problems with it.

If you look at the crank, the 2 pistons in a block are on opposing throws, thus balancing against each other.

Hope this helps

John

1. You are miking the bottom of the bores, right? they wear tapered larger at the top, and will be different sizes depending how much dust its eaten and how long its been run since it was apart last.

2. Never heard it about Molines, but certain Ford engines if the serial number has a particular prefix or suffix letter, it had undersize main bearings from the factory.

The thinking was this: Either we throw the crank away, or else we grind it to the next undersize and put it together "new" with undersize bearings. The same could be done with a slightly oversize, but otherwise good block.

If indeed you do have 2 different size bores, get a machine shop to bore your good smaller bore block to the fit the larger pistons.

Or: This will probably also work and I have heard of something similar being done: use each good block with the pistons that came in it.

(My auto mechanics teacher told of one engine they fixed on a budget that went out the door with 1 .060 oversize piston in it among all the other standard bore pistons.)

1. You are miking the bottom of the bores, right? they wear tapered larger at the top, and will be different sizes depending how much dust its eaten and how long its been run since it was apart last.

2. Never heard it about Molines, but certain Ford engines if the serial number has a particular prefix or suffix letter, it had undersize main bearings from the factory.

The thinking was this: Either we throw the crank away, or else we grind it to the next undersize and put it together "new" with undersize bearings. The same could be done with a slightly oversize, but otherwise good block.

If indeed you do have 2 different size bores, get a machine shop to bore your good smaller bore block to the fit the larger pistons.

Or: This will probably also work and I have heard of something similar being done: use each good block with the pistons that came in it.

(My auto mechanics teacher told of one engine they fixed on a budget that went out the door with 1 .060 oversize piston in it among all the other standard bore pistons.)