What size flex-hone to use on 401

[babywag]

Anybody know what size flex-hone to use on a 401?

[tufcj]

Bore is 4.165" stock. .030 will put you at 4.195"

I'm assuming you use a 3 stone expanding type hone. Grit will depend in the type of rings you use. Cast iron rings like around 400 grit. You'll want a finer grit (600?) for chrome rings.

Bob
tufcj

[babywag]

I thought 4.125 was stock??
(Least that's what the manual I have states.)

I'm trying to save a 401 block someone left outside, need to scrub off the rust to see if it's worthwhile.

[tufcj]

4.165" is factory bore.

Max recommended overbore on a 401 is .030" without a sonic check, the walls get very thin at .060". I've heard of guys going to a 4.250" bore (.085" oversize) with the block partially filled.

Assuming it's factory bore and very minor rust pitting, it may clean up at .030. Remember that a .030 overbore only removes .015 from the wall. Any major rust pits and it may not clean up. If only a couple of cylinders are really bad, you could consider sleeving them, which runs $80-100 per cylinder.

But you figure that the last 401 was built in 1978, the newest ones are approaching 30 years old, so any block is worth an attempt at saving.

Bob
tufcj