guidance on O-ringing a block

putting a spare motor together and have a question about o-ringing the block. most likely will start out with the motor 4.25 bore but want the option to bore it another .060 if needed later. how will that affect where the block gets ringed (or is it rung?)? do i place the o-rings 'out' far enough to allow for being bored later? how far out from the bore's edge do most of you guys put'em? thanks...

btw... i'm poor so this is an iron block chevy it saves me money on ballast... ha ha

 

It's more about what your chamber looks like rather than your bore size. About 4.800" o.d. on the "o" ring groove. I know this sounds big but you have to get around the edge of the chamber at the intake and exhaust valves. This will leave plenty of room for future boring / honing. This means the "o" rings will come close to each other between cylinders. And receiver grooves in the block will almost intersect. Put the stainless wire in the aluminum head. Then a corresponding receiver groove in the iron block. .041 wire is the most common. Let it protrude about .015 from the head. The receiver groove should be about .055 wide and .020 deep. Hope this helps ya, Good luck.

[ April 21, 2005, 09:47 PM: Message edited by: rpmhiperf ]

 

Sean - check around with some of the other BBC guys. Ours (cast iron and KB Olds block) had a center to center measurement of 4.750" on the groove. I think that this may be a standard - if it is, you might find extra heads and blocks that are cut at this dimension. It could save some machine work on spares in the future if you can get close to a standard. Hope this helps...