Has anybody tried boring a 256 (3.625" bore) to the same bore as a 292 (3.75")? I have a 256 block that is going to need some work anyway (#8 cylinder is badly scored), so the thought of boring and stroking it to make a 292 has slipped into my mind.

I don't mind the 239 that is the stock engine for my trck, but I admit I wouldn't mind having a few more ponies under the hood.

 

First, determine minimum amt you need to bore to clean up the scored cylinder.

Second, have the block sonic tested (there was some machining/casting drift back then that can leave more metal on one side of a cylinder than the other). This will tell you the min and max bore you can run. I won't tell you how much wall thickness you need, talk to your machinist/engine guru.

Third, find pistons and rings that have the right pin height and fit in the range determined in step two.

TC

 

My suggestion would be to get a 292 block out of a late 50's vehicle. They have a stronger bottom end, are plentiful, cheap and don't have the problems the 312's have with cracked rear mains. They are also generaly meater blocks so you could bore and stroke this for the same money and get alot more power. The other thing is that the 239/256 motors have smaller intake runners on the heads along with smaller valves all the way around. Go check out all of the tech info on Mummert's site ford-y-block.com or go to the Y-block discussion group. Both of these sites have tons of good info about the wonderful old Y-block. Also you will want to find a machine shop that has actually worked on these things so they don't botch the job or turn the oil slinger off of your crankshaft while you're getting reground for strokin'. Good luck.

 

I have thought about going with a 292 block (and there is no garauntee I won't), I just thought that since I have this block laying around, I ought to do something with it . You're dead right about the heads, though! There is even a difference between the 239 and 256 heads, though the biggest single difference is that the 256 heads have valve rotators, which I understand was not that unusual for truck heads at the time. To say the #8 cylinder is scored is actually an understatement. "Gouged" might be a better term. It's in pretty bad shape. Unfortunately, the rest of the block is in pretty decent condition.

As for the 312, I wouldn't touch one with a ten foot pole, just because of the aforementioned problems with the bottom end.

 

I think the short answer to your question is yes, it can be bored out to 292 specs. I've never done it but I heard more than once that it has been done without issues. If you have a chance, try this idea; pull the freeze plugs out and use a set of drill bits to see how much space there is between the cylinders. I have a 292 and a 312 in my garage and I can do the same to compare. I'm going to guess that it will be pretty similar. If there's a significant difference between my blocks and your block, like if you have bigger spaces, then you'd better do more homework. But if they're the same, you are probably good to go.

While I'm giving out free advice, here's more; whatever you do, be sure to zero-deck the pistons.

For a basic truck engine, I wouldn't be afraid to use the original heads and intake.