Maximum Cylinder Bore for the 225?

Ok, so I've spent the last couple days googling whenever I have a chance, and I can't seem to find anybody that can tell me how far you can *safely* overbore the cylinders in a 225.

The only reason I ask is my 225 recently sucked a piece of the carb into the #1 cylinder and bashed up the Piston and Combustion Chamber on the head pretty darned badly.

I've got the engine torn down, and have found that it's already got .060" oversized pistons, now the cylinder wall in #1 is still smooth, as are the other 5 cylinders, and at .060" I'm not having any cooling problems (hell, it was running damned well before it sucked that thing down the carb)

So what I really need to know is, if after mic'ing everything this weekend, I find that I need to bore the motor, how far can I go, if I can go any larger, before I'm better off just looking for another motor?

 

That's good to know, I thought I remembered reading .120" or .125" somewhere, but I was looking for confirmation on that.

 

Don't know about the 225 specifically, but in general, it all depends on core shift.

I expect you can go 120 over with a selected block, but I also expect that not every block can go 120 over. That's a lot of material, and the 225 is pretty light.

Pick your minimum wall thickness, and sonic check the block. Realize that thin spots are not that weak, but they make the engine overheat.

Supposedly you can also go way oversize if you are willing to sleeve the block.

 

Oh, if I have to go that deep, I'll look for another motor, hence the reason for hauling the block over to my dad's place this weekend where he's got all the appropriate measuring tools, and figuring out if it even needs any machine work....

I've sleeved (well, I didn't *personally* sleeve it) a 302 Ford before, and I was less than happy with the end result, if I was going to go that far, I would just look at a V8 conversion for this application.

And really, I'm not looking to make this engine build more power than it already does, but not having it constantly burning oil because theres scoring on the cylinder wall would be a nice thing =]

It didn't burn a drop of oil before my little FOD incident, and I'd like it to remain that way if I can determine putting it back together is economical =]

 

Yup. Custom pistons for a 225 are VERY expensive. Damhik.

A block that is sleeved correctly can in some cases outlast a non sleeved block. The key is correctly. Very labor intensive (read expensive) to do right. Generally not worth it for a stock rebuild.

 

Is that a 30-over for the 231? Same piston? I had thought that the 231 piston was just a 50-over 225 piston. If so, there should be something 70-80-90 over available at off-the-shelf prices.

Go to the Sealed Power catalog and it lists 20, 30, 40 and 60 oversize for the 231, which would give you 70, 80, 90 and 110 if the pistons were compatible.
http://ecatalog.federalmogul.com/Ap...A&cat=Engine&subcat=Cylinder Block Components

 

You can also check out the Silvolite catalog, which shows both the 225 and 231 pistons. http://www.kb-silvolite.com/assets/09_silvolite_catalog.pdf

Compression height for the 231 pistons is 30 thou less, which could be made up in the head gasket thickness? It would affect your quench height, but it also gives you an opportunity to raise the CR by decking the block and using an OEM-style 225 head gasket. Warm up your calculator...

 

Silvolite pistons say 8.3 CR for the 225. I would think that 9.5 would push you into premium gas territory, without a knock sensor.

 

See, I knew if I gave you fine fellows a few minutes to warm up the info would start a flowin =]

At the moment I'm still determining whether I actually *need* to bore the block or not, but it's nice to know what my options are =]

 

9.0 compression ratio is standard for 225 Dauntless.
7.4 C.R. was the California standard

I don't have experience but I also suspect that 9.5 C.R. will probably start knocking on uphill climbs when burning 87 octane.