Minimum cylinder wall thickness on boosted motor

[WConley]

So sleeves are stronger than the original iron, even though the original iron has to bored thinner to fit the sleeves? How thick of sleeve is best, and what material? Lack of port flow is why all the boost. I have about 175 cfm intake.

I'm not up on the latest as far as what sleeve to use.  The problem with block iron is that it's not as stiff or uniform as a sleeve.  When loaded hard it will go out of round.  Sleeves are designed for maximum hoop strength, with much higher quality material.  With that engine it should be possible to put in a decently thick sleeve while leaving plenty of support wall in the cylinder.  A guy who really knows flatties would be your best bet for specific info.  Maybe sleeves aren't a good solution on your specific application, but for general max effort builds they will give you more horsepower.  Who knows - maybe on your engine installing sleeves would hurt cooling though...

[cammerfe]

Under the sort of conditions you offer, Carl Holbrook was a fan of using very high quality sleeves and furnace brazing them into a thoroughly cleaned-out block. He did at least one project using 4130 seamless tubing for sleeves. It's a hi-buck approach, but it'll give you strength you won't find any other way when you're starting with a factory block.

KS

[WConley]

Yes - Carl told me the same thing when I bought parts from him in the early 90's.  I wasn't going to mention furnace brazing (even though it's the very best way to install sleeves), because it's so danged expensive and hard to do.  You have to re-machine the whole block when you're done.  It would be tough to find the right person to do that nowadays...

[Hemi Joel]

that is something to consider. Here's the thing about this Flathead block: all of the many hours of port work are going to be done on the block not the heads, as well as the five main conversion. so I'll have a lot tied up in the block. Making it last is a priority. it's different than with an overhead valve or if you are at the block you still have your good heads.

[Hemi Joel]

The flow testing was done through the cylinder with a Flow-quik tester. With a head and valve in place, and a 1/4-20 bolt in a dummy lifter to open the valve. 1 turn = .050" lift. I think I will need 22 lbs manifold pressure to overcome the restrictive ports and get enuff air/fuel into the cylinder.

[frnkeore]

Something that may help the intake flow, is a 3/16 to 1/4" radius on the corner of the top of the block, in the intake area but, you'll have to make sure your first ring is below that.