427 cylinder walls

[chris_r]

i need some help does a 427 side oiler service block have thicker cylinder walls than a 68 427 side oiler passenger car block?  what can i bore a 427 service block to and be safe?

[cammerfe]

Particularly because of the value of the block, it makes no sense to haul out the boring bar without a thorough sonic testing session. All original FE blocks were made after FoMoCo went to a 'thin-wall' approach to the casting process. Boring by 3/16ths or more, common with the flatheads, simply doesn't work with later iron.

As a general rule, 30 thousandths is OK with an 'as-produced' FE block, but the only way to tell for sure is to do a sonic test. And be sure the guy doing the test knows what he's doing.

KS

[chris_r]

O yes i would sonic test .  Well i was thinking about buy a block but the block is at 4.270 now so i think i'll pass on it

[jayb]

I'd say it would depend on the price.  I bought one at 4.27 bore once and went to 4.293 with it (.060" over).  I had some thin spots in the walls (.075-.085 in a few spots), but I used it as a dyno mule and it has run hundreds of pulls with no problems at around 650 HP.  I bought my block for $800 because it was already bored .040" over; if you can get an equivalent deal it might be worth the risk.