Cylinder wall thickness

[theman440]

A question for the engine builders here on CR - What would be a minimum cyl wall thickness you would want to see? The block is a factory Mopar 440 for a bracket car shootin for 700-750 hp.

Thank you

[GTX JOHN]

I would want .175 or more at finished overbore in a big block mopar or .135 in small block mopar.

[theman440]

Thanks John,

Are you back in town? - you happen to have a sonic checker? call me I still need some wheels.

[Paul Precht]

The only blocks that are that are thick are the 413 industrial and motorhome, most 440s are less than .175" before boring and 700HP would be about the safe limit IMO. The aftermarket blocks are the way to go if you can get one. The 400 blocks are a bit stronger in the web area and more rigid due to the shorter cylinder length. A 400 block filled Halco machine grout and Pro-Gram Engineering main caps would be a good start.

[Todd Gross]

There were some thick blocks in 67-69 era. Back when I was more adventurous, we took some old blocks, filled them, bored/honed to 4.560 and put a 4.625 stroke to make an alcohol 604" It required a main girdle and good caps to hold things since the cylinder walls were at .060" +/- a little.
They didn't stay round very long as one might expect. That was back around 1990 and the only aftermarket blocks were KB. Thought it was worth a try. It wasn't.

[GTX JOHN]

We have seen thick and thin blocks......No matter what year
the 440 blocks are. Just have to check them.

[SST3193]

I bought the 440 out of a 1971 New Yorker and it had the thickest cylinder walls, at about .220. That block also had water pump bosses cast into the back of the block, over the top of the bell. I assumed it was supposed to be a boat part.

[Frank Castros]

I have a friend who had a 426 NASCAR (Petty) Wedge block that was stupid thick on the thrust side. How many of those are out there.

[Chuck Gallagher]

Jeff:
Engine blocks are like home made cakes from an oven. The quality really depends on the ingredients, and the maker, and the available controls as to how well they turn out..
Two identical (brand) blocks from different foundries, both following the same prints, are not usually going to be the same. A block with a higher carbon content and precision casting core control could be more likely to hold the cylinder walls shape (round and straight) and have stronger main webs then a much thicker block that had lower carbon in the iron and poorer control of the casting cores.
High volume production blocks generally are not going to result in castings that will hold their shape at the horsepower levels (600+) racers want. This is why todays purpose designed racing blocks are, in the majority of cases, cast using compacted graphite which is more robust but also more expensive.
So before investing in machining any recycled production block, I would recommend that you test the block for hardness of the material and the amount of core shift that may be present and if a new racing equivalent is available from a reliable source.
You don't want to end up with an engine with a cracked main web or seven perfect and one bad cylinder.
Chuck Gallagher

[Rich Biebel]

What Chuck said is accurate and back in my engine shop days we hardness tested and sonic tested most Small Block Chevys and any block that was going to be potentially used for a race engine....

The Hardness test was easy using a Brinell tester and the blocks had a pretty wide spread on the numbers that you got on the test..

An ideal block was at the high end of the hardness scale and had thrust walls that would be .200" or more when finished.

You can easily see a badly core shifted block just by the cam hole and the machined surface at the face of it. The sonic test will show the cylinder walls being offset usually on a block with visible shift at the cam hole...

I was buidling a 383 for a friend and the block was so offset I could not get rods to clear one side at the bottom of the cylinders and the other side went right by......I changed what rods I was using for it just to make the fit and not grind the heck out of the block and potentially break thru to the water jacket....The crank and cam were not centered in the casting by a fair amount.....GM had some real odd ways of machining engine parts.....BB Chevy Iron heads is a good example.......Guide bores not centered with the guide OD

The Brinell numbers were from a low of around 200 to a high of around 245.....

A nice early 4 bolt 010 block with nodular caps was the best you could hope to find with good hardness and cylinder wall thickness....

Aftermarket blocks are a ton better......