360 .060 overbore too much ??????

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woody30

woody30

woody30
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Just wondering what is a safe overbore on a 360 block. Do all the things like what year block, core shift, etc come into play, or is .060 safe on any 360? I have that race block bored .060 but filled to within 1 1/2" to 2" to the top in the water jackets and have corresponding stroker kit to go with it. I'm assuming the race block filled that high won't work for the street. I would love to use the stroker kit for the street. I have an 87 360 (standard bore) for a spare block and also a 72 360 .030 assembled short block. Will either of these work for .060 overbore with no problems??
 
Agree with the sonic tests but also keep in mind that the factory service manual says no more than .040 overbore.
 
Have it sonic checked, but I have done at least 5 of them at .060 over with no issues.
 
i did mine 60 over...took me 3 blocks to get that...bad sonic test after sonic test..but its what i wanted....and i got it....been running strong for last 3 years...and im pretty hard on it so fingers grossed
 
Vs29H1B said:
Agree with the sonic tests but also keep in mind that the factory service manual says no more than .040 overbore.
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If you believe that "Stop @ .040" stuff, I got a bridge to sell you.
Sometimes it can be less, sometimes it can be more. Sonic checking tells the true story.
 
Well, Hensley Motorsports has been boring 318s to 4" for close to 20 years makin 402 stroker motors. That's .090" over in case you flunked math. As Rob said, sonic checking is the only way to know for sure, but generally they will all stand .060 over unless they had core shift real real bad.
 
I have heard of .070 over 360s sonic checking out fine and some .030 sonic checking out thin.
 
rumblefish360 said:
If you believe that "Stop @ .040" stuff, I got a bridge to sell you.
Sometimes it can be less, sometimes it can be more. Sonic checking tells the true story.
Click to expand...

That's right. I once read of a 360 that sonic checked good enough to bore out .100" over. Then others fail at .040 over due to core shift in the bad direction.
 
I read somewhere that the best 360 to use was the 1971 blocks. The reason? The rumor was that the 71 year 360 was built using the 340 casting cores. This explains why 360 engines used the 340 style left engine mount.
340 engines had a standard bore size of 4.04 inches vs 4.0 for a 360. Assuming a .040 limit ( Yeah, sure!) If a 340 could be bored to 4.080, a 1971 360 should be able to be bored .080 over.
Of course, I would suggest a sonic check.
 
This is what I seen and or read in the past. 71'-73' 360 blocks where cast the same as 340's so there much thicker. I've seen a few 71'-72' go to as much as 4.100" without issues. I've talked to other mopar builders and they've seen 4.125" bores with no core shift. I do believe after 77' it's a crap shoot on thickness. I had a 85' 360 in a friends duelly fresh rebuild bored to 4.060 and it used oil like crazy to the point where I knew something wrong. The motor was built by the same builder that does my race motors. He sold that beast no telling what happened. Sonic check everything as others have suggested and you'll be in a better place.
 
Guess I don't have to use .060. The pistons were higher compression than the guy told me. He said 11:1 comp. it's 11.8:1. Big difference. Can't use them on the street. If I do new pistons I have a .030 block ready to go or a standard block. Won't have to worry about .060 and all that. 1 block is already .030 and freshly honed. The other one is a standard bore block that's never been apart. Thanks for all the tips guys. I appreciate it.
 
OLDSTYLE said:
Have it sonic checked, but I have done at least 5 of them at .060 over with no issues.
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Old style
How is your .60 360s holding up? Found a block that is 60 over but I want to stroke it. Wonder how it will hold up
 
A thicker bore, will make more power than a thin bore everytime.
 
Food for thought.........Most resent build I have done, am going .030 over on a 360, first block I put up for machining sonic checked .090 thick in the minor thrust at standard bore of 4 inches, was an 80's block

You can't go wrong if you have it sonic checked, but you certainly can go wrong if you don't
 
If memory serves correct, the older 360 blocks came from the 340 with a 4.00 bore. You can bore .060 but still have the block checked first
 
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