Just found out after a fresh .030 over, bore & hone that there is a scratch in #2 cylinder caused by the boring bar. It runs from the deck all the way down the cylinder, about .002 deep. Don't really need to get into how or why, its there now, stuff happens. The machine shop is willing to sleeve the said cylinder. Comments on sleeving the one cylinder, VS boring .040, which will require balancing pistons, selling already pressed on pistons & rings?
-
-
Re: '66 427 cylinder sleeve
If it's just a single scratch .002" deep I don't think it's going to cause a problem A light hone to knock off any high spots along the scratch should be done if the scratch occured after final honing. If it occured during boring, but before final honing, just put it together. I've seen a lot worse looking cylinder walls that didn't cause any major problems.
My Cosworth Vega's #2 cylinder has some light scoring and a casting porosity hole about .060" by .030" halfway down. It leaks down (checked at TDC, halfway down, and BDC with cam belt disconnected so the valves remained closed) only about 1 psi more than the other three.
After I refreshed the head (The valve guides/seals were worn REAL bad, which is why it consumed a lot of oil, but it wasn't down on power.) and reindexed the cams I can't even measure the oil consumption, and it pulls from less than 1000 revs to over 7000 and makes one SAE corrected RWHP per cubic inch on a 8.2:1 CR and regular unleaded.
The short block is the original Tonawanda build with 72K miles. Bore wear/taper is nil.
Either sleeving or boring to .040" - I think the "cure" is worse than the disease.
Duke -
Re: '66 427 cylinder sleeve
if the block was honed without a deck plate you will have more leakge from a out of round cylinder than from that scratchComment
-
There's another alternative...
to sleeving the scratched cylinder or stepping up to 40-over. Your machinest can order a set of hand selected pistons direct from the mfgr (only 'standard' sizes are available off-the-shelf through distribution). Most of the classic Ford guys know this 'trick' because they're dealing with thin wall engine block technology and definitely want to minimize the overbore to maximize the number of rebuilds they can squeeze out before facing the ultimate day of having to sleeve all eight holes...
The last time I overhauled my '70 350, it was at 40-over and bore scope analysis showed it would 'make' at 42.5-over versus going all the way up to 60-over. So, after a $25 special handling fee, a set of 42.5-over pistons were made and shipped in. She runs FINE at 42.5-over.
So, here's a third alternative to consider. It's all a matter of economics and judgement. Which is cheaper/better for you: (1) a sleeve job on one cylinder only and keep your existing piston set, (2) over-bore all eight holes and step up to a standard sized set of pistons, or (3) over-bore all eight holes to the MINIMUM necessary and special order a set of hand-selected pistons to match.
If done right, a sleeved cylinder can actually be BETTER in terms of longevity than the block's native cast iron cylinder wall surface...Comment
Comment