Sonic checking my 71 360 block

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HuntedDuckV351

HuntedDuckV351

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So I'm currently building a 360 stroker motor and so far I've bushed the lifter bores, deburred the the block. Now I'm working on sonic checking the cylinders. So far I've checked 1357 in the middle of the bore a d I'm getting anywhere from .200 to .230. I checked the top of the deck on 1 and 3 and it was around .250-.260. This is an already 4.030 bore. I will probably need to take this to .040 over. This will be a 600ish HP motor. So far so good on the numbers? What is the No good number?
 
So you’re at.030 over now and you are taking out another.010? .005 a side of the cylinder?
 
I would be good with that, have you talked to your engine builder/machinist?

I would think you would have sonic checked before you did any other work on the block.

.005 a side probably can be honed out. Make sure you can get pistons in that size. Custom pistons cost more than off the shelf. Seems like LA mopars are not an off the shelf item anymore.
 
Yes I should of checked it before I started but I didn't. My mistake was thinking it was a standard bore block. Friend gave it to me out of a 74 Dodge Motorhome that he had forever.

I can get 4.040 pistons. Having a set made at wiesco as I will call and just have them made .010 bigger.

I was doing the sonic checking as my machine guy let me barrow the sonic checker.
 
ch1ll said:
I would be good with that, have you talked to your engine builder/machinist?

I would think you would have sonic checked before you did any other work on the block.

.005 a side probably can be honed out. Make sure you can get pistons in that size. Custom pistons cost more than off the shelf. Seems like LA mopars are not an off the shelf item anymore.
Click to expand...
Speed pro has pistons for the 360
 
Any spot under .100 would definitely concern me. Over .150 everywhere? You're gold imo.
Thicker is better, of course.
 
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ch1ll said:
Funny, I heard early teeners had the same block casting as 340’s and could be bored to at least 4.07 contradicting what he said about 318’s.
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Are you sure "they" werent
ch1ll said:
Funny, I heard early teeners had the same block casting as 340’s and could be bored to at least 4.07 contradicting what he said about 318’s.
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talking about a 318 POLY?
 
33IMP said:
Any spot under .100 would definitely concern me. Over .150 everywhere? You're gold imo.
Thicker is better, of course.
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Thanks for the info. I was checking the passenger side bank and fou.d a spot that was .177 but of I moved it a 1/32" it would read .220 move the other last that .177 and it would read .220 again being moved a 1/32". Sounds like I have a pretty descent block to start with. Sounds like Shady dell was good on anything over .125
 
To do a sonic properly....
Check the cylinder at 0°, 90, 180, and 270, at the top of the cylinder, middle, and bottom, and write down the numbers.....
then do it seven more times.

It does sound like your block is pretty good.
 
33IMP said:
To do a sonic properly....
Check the cylinder at 0°, 90, 180, and 270, at the top of the cylinder, middle, and bottom, and write down the numbers.....
then do it seven more times.

It does sound like your block is pretty good.
Click to expand...
I will tackle this tomorrow and report back with he numbers. Where I found that .177 number as at 45 degrees and 2" down the bore
 
HuntedDuckV351 said:
Thanks for the info. I was checking the passenger side bank and fou.d a spot that was .177 but of I moved it a 1/32" it would read .220 move the other last that .177 and it would read .220 again being moved a 1/32". Sounds like I have a pretty descent block to start with. Sounds like Shady dell was good on anything over .125
Click to expand...

That’s what you will find when you start sonic checking as many blocks as you can. There is literally zero consistency because they are castings.

I wouldn’t be afraid to take that think to 4.100.
 
Just got some work done myself. Never thought of a sonic report. Ill have to quiz my machinist about that.
 
I have my own sonic checker and don’t bother doing mine at .030 over. Usually by time I’m worn out at .040 it’s been rebuilt 4 times so I throw it on my scrap pile and start over at .030
 
HuntedDuckV351 said:
Let us know what you find out. Haven't got to sonic checking all the cylinders yet. Try this weekend.
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Just went .060 over on a 340. They said it's fine but I didn't hear any numbers. I'll pick it up next week.
 
Sorry it took.so long but life gets in the way sometimes.... so I did get around to checking one bore today. Number 2 cylinder. And here are the results of how I did it.. if wrong please et me know the way. I did 0 which was down 90 towards the back 180 towards the lifter bores and 270 towards the front and I went an 1 inch down 3 inch down and 5 inches down front the head deck.

0 was .255 .245 and. 290
90 was .245 .245 and .275
180 was .309 .319 and .400
270 was .280 .276 and .401

First number is 1" 2nd number is 3" and last is 5" down
 
My late '70 360 block was sonic checked when I sent it out to be machined. Can't recall the numbers but I was told it was good at .060. Early 360 blocks,'71-'74, were supposedly cast with the same water jacket cores as 340's.
 
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