sonic check

[73chargers4404]

 I took my block in and had it sonic checked and the guy doing it said i  should have no problems with it ,it has been bored 60 over .i was wondering what would be a unsafe tickness for a block.does anyone have any ideas.the papper i received shows every cylinder the tickness of the top /bottom and both sides of each cylinder pretty cool process.

[73chargers4404]

Here what the work sheet looked like my scanner is broke so i had to make my own on paint ,i used all the specs off the test sheet.

[firefighter3931]

Those numbers look really good...excellent in fact for a factory block. The critcal dimension is the major thrust side which is the passenger side of the cylinder wall on both banks....looking at the engine from the front. That block is an excellent candidate for a performance build or a stock build for that matter. 


Ron

[Ghoste]

Why wouldn't the major thrust side be the outer wall on both banks?

[firefighter3931]

Why wouldn't the major thrust side be the outer wall on both banks?

Think about the rotation of the crank and which side of the cylinder gets side loaded. 


Ron

[Ghoste]

Okay, gotcha.  But now, isn't piston offset in oem applications always to the outside?

[73chargers4404]

im just glad it checked out ,its a 78 casting block so  i thought i would have it checked out to make sure it would hold up .whats the smallest number  could it be for a block not to check out good

[John_Kunkel]

im just glad it checked out ,its a 78 casting block so  i thought i would have it checked out to make sure it would hold up

Another nail in the "thinwall casting" coffin.

[andyf]

That is a very thick block for a Mopar.  Very rare to see numbers like that from the factory.

[MOPARHOUND!]

What's the smallest number could it be for a block not to check out good?

Based on the limited understanding I have, the number was .120".  Your numbers are after the .060" overbore, or?

Checked around some, and found this comment by a brand "X" racer:

"I haven't seen any specific guide lines regarding minimum cylinder wall thickness and that's probably because of different block constructions and the different materials being used.

I try to maintain at least .090" for the minimum thickness and the more the better. There is the major thrust side in the cylinders that takes the most abuse and subsequently these should be left thicker than the opposite or minor thrust side. The Major thrust sides would be the outside of the cylinders on the passenger bank and the intake valley sides of the cylinders on the driver's bank.

Where you run into a problem is when the major thrusts in the block are already thinner than the minor thrust sides. This is where sonic checking really proves it's worth as you can weed through the less desirable blocks."

Horsepower level is another factor in what is acceptable for cylinder wall thickness.  Some of the aftermarket race blocks are .300" minimum or more.

Question I would pose (not to hijack the thread), is given the #6 cylinder at .135" being the thinnest, this block could be bored another .030"?  That is, .135"- (.030"/2)  = .135" - .015" = .120".  Using the .120" minium as being a "safe" number for cylinder wall thickness.

??

[andyf]

Yeah I'd say that block could go even bigger than it is at the moment.  It is 4.380 now correct?  So the next logical size would be 4.400 I think but I'd have to flip thru a ring catalog to see what is offered.  Maybe go 4.390 which is a 0.030 over Ford 460 size?

I checked JE rings and 4.390 is the next size up from 4.380 for rings.  Next size after that is 4.440 which would be pushing it with that block.  A 4.440 bore with a 4.250 stroke would be a 526 motor which would be cool.

[Chryco Psycho]

I have heard minimum is .125 but that would be thrust side , other late blocks I have checked have had  similar wall thickness , great candidates for HP builds