Well, not boring to some. What I mean is enlarging the bore. How much meat can be cut off of the cylinders of a 272, or a 292. I have blocks of each of these that need bored out . Can a 272 be bored to accept std. bore 292 pistons? My 292 block has severe rust but might clean up at a maximum bore. I guess piston availability is the real determining factor.
sonic test the block...that will tell you how much meat is left
A 292 and 312 Block are the same castings. A 292 is a 2.750 bore and 312 is +.050 at 3.800. Normally a 312 will go +.030, so the final bore is 3.830. A .080 overbore might be enough to clean up your cylinders. I always sonic check everything I build now. There is a lot of chance of core shift.
Over bore to the .030 312 bore and get a set of John Mummert's(FordY) new rods that allow you offset grind a 292 crank to 312 stroke and use 312 pistons. With that combo, you would actually have a 312 in your car. That 20+ inches makes a lot of difference in performance.
A 272 block is a different casting, can often be(should be for HP increase) bored +.050 to 292 standard bore, but that's it. A +.050 272 would use stock 292 pistons and be a 292.
Very interesting topic ! I had my other 292 project bored out to 0.080over which is a 312 +0.030 like said before. I am using a 312 crank with it's main journals turned down to 292 main specs. of course will be using 312 rods.
I don't think that you could use 292 pistons(fe 292 +0.030 =3.78) with a stroked crank ( or 312 crank), as possibly the 292 piston skirts would touch the crank in BDC. the 312 pistons are shorter on the skirts. The compression height ( piston pin to top of piston) is the same on 292 and 312.
My engine machine shop hsaid they would not expect any trouble in boring the 3.75 to 3.83 and you can use readily available 312 030 over pistons. Like Gary said, sonic testing would be the utmost insurance.
Quote from: suede57ford on 2017-02-26 22:39
With that combo, you would actually have a 312 in your car. That 20+ inches makes a lot of difference in performance.
what do you mean by that ? I wasn't expecting much more power increase than those 7- 8 % of cui. Does the longer stroke have much effect on compression or cumbustion chamber efficiency/ flow? I'd be very interested in what makes the difference.
I had picked up a set of domed Jahns 292 pistons for my 57. Didn't want to put new pistons in old holes so I found a 272 to work with. In researching my project I found it was regularly done "back in the day" without sonic checking. Talking with the machinist he said he'd have to send the block out a hundred miles away to have it checked. Not every shop has the ability to sonic check blocks. He said he had done many of these so we decided to go without the sonic check. Fast forward 10yrs. it runs fine, doesn't overheat here in Az. or use oil.
All that said, I started out with a good, clean block and not one with rusted cylinders. In your case I agree with gasman and it would be worthwhile to have it sonic checked.
Boring a 272 block to standard 292 bore has been a common practice for years, I've built a few that way and without issues. I built my current 292 from a 1955 272 Dearborn block.
Any increase in Cubic Inches does increase the Compression Ratio. That is a major bonus. With modern composite head gaskets, the compression is already really reduced.
Even with increased CI, you still will not be able to get the compression ratio up past safe pump gas ratios with stock flat top pistons.
Increased compression will help performance and efficiency(mileage).
You can estimate 1HP for every 1 CI increase, Example: 20 CI increase = 20 HP. That Increase will be at the lower RPM range in the form of more torque which you will notice when driving.
So to boil this down for a relative novice, I can simply bore my 272 out to a 292? Crank and rods are the same? Nothing more needed than new pistons? This site is awsome!
Thanks, Rowen
I drove a 312+.040 for years, no problems.
Ron.
Thanks, guys..I only want a y block for nostalgic reasons. If horsepower was a motive , then the y block would be low on my picks of Ford motors to use. High on the list would be 385 family, the Windsors, or Cleveland. The 427 would be my choice for good looks and performance from the FE offerings.