My new Y block is a 55 to 57 272 and is the bore the only difference between the two motors and if thats the case is the block thick enough to bore it to a 292 size.

Butchering up everything I can get my hands on in Dayton Ohio

In most cases, yes.

John - "The Hoosier Hurricane"

The majority of the 272’s can be bored to the standard 292 bore size (0.125” over) but there are those rare few that have core shift or block imperfections that prevents this.  Sonic checking the block before boring would be the only way of knowing this for sure and preventing some possible headaches later.  Even blocks with heavy core shift can occaisionally be salvaged by offset boring using the sonic test data.

Lorena, Texas (South of Waco)

i have a 292 ecg block with steel crank and the "good rods from a early 60s school bus would that be better to use than boring my original 55 272 and using the 292 internals as dont the later blocks have thinner walls ?

y-block newbie

If you already have a suitable 292 block, then by all means use it.  Many of the 272’s bored out to the standard 292 bore size end up being marginally thin and cannot safely support any additional boring after this.  The cylinder walls in the C2 292 blocks are plenty beefy so no problems there as far as some above normal boring goes.  I go 0.110” over on these regularly.  But sonic testing any block being used will help to spot potential casting problems which can be present in any block being considered for use.

Lorena, Texas (South of Waco)

Are you sure its an ECG block with the steel crank and rods? That block was 55 era 272 mostly, the blocks with steel crank were 61 up era, C1TE, C1AE C2AE. You do mention its from a 60's school bus but the original block may have gotten damaged and they installed the components into an ECG block?

Just rmember the Good C1TE rods are the 312 length, the pistons had a taller deck so you cannot just use standard 292 pistons with those rods.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?