Minimum cylinder wall depth for a 318 stroker build

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dfoyl

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I am building a 318 stroker, and my stock-bore block has just come back from a sonic check with "undesirable" cylinder wall thickness..

Here is what I have (reading from top of bore / middle / bottom) :

Cylinder 1: OUTER SIDE: 270 /208 / 241, INNER: 194 / 148 / 186
Cylinder 2: OUTER: 194 / 174 / 208, INNER: 233 / 194 / 219
Cylinder 3: OUTER: 208 / 186 / 223, INNER: 226 / 194 / 174
Cylinder 4: OUTER: 167 / 148 / 174, INNER: 194 / 167 / 241
Cylinder 5: OUTER: 208 / 215 / 174, INNER: 152 / 130 / 183
Cylinder 6: OUTER: 194 / 183 / 208, INNER: 194 / 174 / 223
Cylinder 7: OUTER: 223 / 194 / 241, INNER: 197 / 156 / 215
Cylinder 8: OUTER: 208 / 156 / 204, INNER: 223 / 183 / 324

The numbers I am most concerned with are Cylinder 1 middle inner (148), cylinder 4 middle outer (148), cylinder 8 middle outer (156), and especially cylinder 5 middle inner (130). With a standard 30 thou overbore that leaves me at 115 thickness.

Given the extra strain of a 4" stroker (worse rod angle, higher piston speed), would this be considered unacceptably thin for a mild street motor ?

In Australia 318's aren't impossible to find - they're relatively common compared to 360's - but they aren't exactly laying around in wrecking yards either (there never were that many sold here, and the ones that are still around aren't cheap by US standards). I don't want to go 360 for a few reasons.

Any and all opinions welcome :-D

Dean.

EDIT: Sorry, title should have read wall THICKNESS but I can't change it :) DUH.
 
It's too thin. #s 1, 4, 5, and 8. I think too, your tester should be a little more specific. There is major thrust, and minor thrust, and checking a 5" tall cylinder in 3 spots isnt enough IMO to show a real trend. If that was in front of me with any performance work in mind beyond "stock with a cam" I would more than likely toss it and find another one.

Kudos on having the testing done tho. Much cheaper to find a "maybe" before you machine the whole thing...lol
 
I've always heard and used the .200 min major and 1.50 min. minor. I know some go thinner then that but in the end its your money.
 
Sorry in advance for what may be a silly question - but by major/minor walls are you differentiating between the walls between the cylinders and the walls that are on the sides of the intake/exhaust ports?

Thanks
 
koryliss said:
Sorry in advance for what may be a silly question - but by major/minor walls are you differentiating between the walls between the cylinders and the walls that are on the sides of the intake/exhaust ports?

Thanks
Click to expand...

Cylinders 1,3,5 and 7 the major is the side of the cylinder wall closest to the lifter valley area and the minor is toward the outside of the block. Cylinders 2,4,6 ad 8 the major is toward the outside of the bock and minor is towards the lifter valley. Another place to sonic check is the front of cylinders 1,2 and the back of cylinders 7,8 I believe .180 is the min. there. Hope this helps.
 
Limits will vary by builder. I use minimum .150 on major thrust, .090 min in the pin axis because finding all 8 that are more is not quite a needle, but call it finding a croquet mallet in a hay stack. I've sleeved one hole in several blocks because they were all thick...except one...lol. I wouldnt waste money sleeving any 318 block.
 
Thanks for all the replies guys. I have another block lined up and hope to get better figures out of it 8)

I'll try to get more dimensions down the bore (I do have front-to-rear but didn't list them to save on typing!)

Dean.
 
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