Chamfer at the top of 440 cylinder bores...

How much did the chamfer on cylinder bores vary with standard bore 440 blocks?

How much chamfer would be too much or excessive?

The later ones have some pretty huge chamfers, some of which of course goes away when you deck the block. In an extreme case you might need a head gasket with a larger bore so the fire ring doesn't overlap the chamfer; Cometic offers them but they're fairly expensive.
Hopefully you have the complete motor and can look at the old head gaskets & heads to see if there were problems; but with 440 pistons being so far down in the hole on the later motors with the large chamfers, the decks need to be milled a fair amount anyway.

Yep, some of the blocks machined in the late 70's had huge chamfers in them. Guess the guys on the line were drunk or something. I've had 440 engines where I had to use a 4.50 bore head gasket because the chamfer was so big.

I had to use a 4.5" gasket on my .030" over bores.

We just noticed that on my 74 440. The machinist said not to worry about it so long as we get the right head gasket.

Bored .030 and it looks like someone was just drunk as can be, but thankfully it isn't a problem.

Glad... but not so glad to hear that it was a fairly common problem with the RB engines and probably others.

A friend of mine called the champfer the "fire ring". He said that it promotes comcustion (?)

He claims that he had a race engine without the champfer and it didn't run well until they had another machine shop redo the bore. then it made great power.


What are your thoughts? I always considered this fishy!

The fire ring is the metal edge of the head gasket that faces the bore; so called because it's a ring (though not necessarily round) that faces the combustion heat.
Not enough info on your buddy's engine, but there could be many reasons why re-doing it would make more power, or why the initial build would lack power.
Unless a chamfer at the top of the bore helped unshroud the valves (more accurately the flow in/out), I don't know how it would make power. It seems to be there to speed up piston installation on the assembly line and to make it harder for the rings to hang up on the edge of the bore.