Having my motor sonic tested before dumping $$ into a stroker kit etc. What should be minnimum wall thickness?
Thanks, Toby
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Less than .135 not good on a thrust side of cylinder wall
0.120" on the thrust walls, 0.080" on the non-thrust walls, maybe even tolerate 0.075" on a non-thrust wall in a spot here and there, especially if those spots are in the lower portion of the cylinder thats not pounded by the exploding mixture.
Don't write a block off if it's thin, you can always sleeve all 8 cylinders, end up with a block thats more durable and makes more bhp.
When you have any block work done, find the guys who have the best CNC machines possible, and know how to use them. You want the cylinders "indexed", not just bored.
The more accurately a block is machined, the more durable it is, the less it beats itself up as it runs, the more power it makes. Money spent on accurate block & reciprocating assembly work is the best money you can spend on a motor that will be run hard. The difference in durability is significant.
cowboy from hell
Don't write a block off if it's thin, you can always sleeve all 8 cylinders, end up with a block thats more durable and makes more bhp.
When you have any block work done, find the guys who have the best CNC machines possible, and know how to use them. You want the cylinders "indexed", not just bored.
The more accurately a block is machined, the more durable it is, the less it beats itself up as it runs, the more power it makes. Money spent on accurate block & reciprocating assembly work is the best money you can spend on a motor that will be run hard. The difference in durability is significant.
cowboy from hell
Thanks for the info.
Toby
Toby
Uhhh, which are the "thrust walls"? I'm sure I could guess, but I'd rather get the right answer from the experts. Thanks!
The thrust walls in the picture below are the walls identified as intake or exhaust.
Additionally, many cylinder wall thickness reports differentiate between the "Major" thrust wall and the "Minor" thrust wall.
The major thrust wall is the wall the piston drags against after combustion as it goes from TDC ot BDC. The minor thrust wall is the wall the piston drags against as it is being pushed upward by the crankshaft from BDC to TDC.
In the picture below I believe the major thrust walls are on the left side of each cylinder, unless my old mind is playing tricks on me.
(see how thick those cylinder walls are, this motor was NOT a small block Ford)
take care, George
Additionally, many cylinder wall thickness reports differentiate between the "Major" thrust wall and the "Minor" thrust wall.
The major thrust wall is the wall the piston drags against after combustion as it goes from TDC ot BDC. The minor thrust wall is the wall the piston drags against as it is being pushed upward by the crankshaft from BDC to TDC.
In the picture below I believe the major thrust walls are on the left side of each cylinder, unless my old mind is playing tricks on me.
(see how thick those cylinder walls are, this motor was NOT a small block Ford)
take care, George
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I guess I want to simplfy this...Im still trying to gauge Georges response. Correct me if Im wrong please. But isnt the piston skirt on the thrust side????
Jeff
Jeff
FWIW, there were very few 351 Cleveland blocks ever cast with more than 0.100" wall thickness everywhere. Many will sonic-test at 0.080" or even less in one or more spots. These are properly called boat-anchors, being unsafe above maybe 250 bhp/5000 rpms. I have a 3" long piece of cylinder wall from Larry Stock's SS engine's on my desk right now, and it mikes at 0.073"(the engine fragged itself at 5800 rpms in 5th; not much was left....)
As for the thrust sides, yes-the piston skirts are what apply pressure to the cylinder walls, and the pressure will be higher on one side of the bore during a power stroke.
Note- Chevy guys get nervous when their cylinder walls drop below 0.200"- something a brand new Cleveland block could only dream of! This thin-ness is also why I'm not a big fan of supercharging or big loads of nitrous in 351-Cs- we're running out of blocks, guys! If one needs a mantra to repeat in times of high anxiety, I recommend chanting, "Sonic Test All Cleveland Blocks Before Spending Money To Up Their Power!'
As for the thrust sides, yes-the piston skirts are what apply pressure to the cylinder walls, and the pressure will be higher on one side of the bore during a power stroke.
Note- Chevy guys get nervous when their cylinder walls drop below 0.200"- something a brand new Cleveland block could only dream of! This thin-ness is also why I'm not a big fan of supercharging or big loads of nitrous in 351-Cs- we're running out of blocks, guys! If one needs a mantra to repeat in times of high anxiety, I recommend chanting, "Sonic Test All Cleveland Blocks Before Spending Money To Up Their Power!'