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Offset Cylinder Boring #922413 02/06/11 05:14 PM 02/06/11 05:14 PM
Joined: Jan 2003 Posts: 2,129 Vermont T TrWaters OP top fuel
TrWaters OP top fuel T Joined: Jan 2003 Posts: 2,129 Vermont	I searched for an hour on here and found many references to offset boring of cylinders (side to side....not front to rear) to compensate for block core shift, but nowhere did I find what might be considered an acceptable (or maximum) amount of offset. Are there considerations other than the combustion chambers? Thanks. TR Waters

Re: Offset Cylinder Boring [Re: TrWaters] #922414 02/06/11 05:44 PM 02/06/11 05:44 PM
Joined: Mar 2006 Posts: 9,910 Eighty Four, PA B G Racing master
B G Racing master Joined: Mar 2006 Posts: 9,910 Eighty Four, PA	Boring parallel to the centerline of the crankshaft [IMG]http://i430.photobucket.com/albums/qq21/ajcasini/max_zpsdppwd9km.jpg[/IMG]

Re: Offset Cylinder Boring [Re: TrWaters] #922415 02/06/11 05:51 PM 02/06/11 05:51 PM
Joined: Nov 2003 Posts: 2,503 Illinois CRE2004 super gas
CRE2004 super gas Joined: Nov 2003 Posts: 2,503 Illinois	I don't understand your statement/question. What are you looking to do? The "acceptable" level of offset would depend upon the available material thickness. Then keep in mind you'll have to make sure you have piston pin boss to rod clearance. I've moved them up to .060". Last edited by CRE2004; 02/06/11 07:02 PM.

Re: Offset Cylinder Boring [Re: TrWaters] #922416 02/06/11 06:55 PM 02/06/11 06:55 PM
Joined: Oct 2003 Posts: 7,506 Az Crizila master
Crizila master Joined: Oct 2003 Posts: 7,506 Az	Quote: I searched for an hour on here and found many references to offset boring of cylinders (side to side....not front to rear) to compensate for block core shift, but nowhere did I find what might be considered an acceptable (or maximum) amount of offset. Are there considerations other than the combustion chambers? Thanks. I'm running a 71 360 block with one hole offset bored with no problem. Wasn't done for core shift though. Had some detonation problems with a 408 motor that was already .030 over. Broke a top ring land and did minor bore damage. Had the hole bored for a .040 over slug to fix the damage ( .009 on the damaged side and .001 on the good side. Worked great. I guess I'm one of the few guys that is running a 410 ( or there abouts ) stroker motor. . If I remember, the damage was towards the front of the block, but I would guess you could easily get away with that much offset ( and probably more) anywhere 360 degrees in the hole. Fastest 300

Re: Offset Cylinder Boring [Re: TrWaters] #922417 02/06/11 07:07 PM 02/06/11 07:07 PM
Joined: Oct 2007 Posts: 4,206 New York polyspheric master
polyspheric master Joined: Oct 2007 Posts: 4,206 New York	The change affects the clock position of that piston vs. its crank throw. Assuming the pin eye as the focal point, an RB has a radius of 1/2 stroke + rod = 8.635", = 54.255" circumference circle, = .151" per degree. That makes any re-location almost invisible, like .030" is 1/5th of a degree. Someone check my math, please? Boffin Emeritus

Re: Offset Cylinder Boring [Re: polyspheric] #922418 02/06/11 07:28 PM 02/06/11 07:28 PM
Joined: Mar 2003 Posts: 1,632 Lubbock,TX D DavidDean top fuel
DavidDean top fuel D Joined: Mar 2003 Posts: 1,632 Lubbock,TX	Good Post Im having to offset the bores of my X block. Im having to shift to the front about .050 to correct wall thickness.There's also some good reading at speedtalk.com.

Re: Offset Cylinder Boring [Re: CRE2004] #922419 02/06/11 07:46 PM 02/06/11 07:46 PM
Joined: Jan 2003 Posts: 2,129 Vermont T TrWaters OP top fuel
TrWaters OP top fuel T Joined: Jan 2003 Posts: 2,129 Vermont	Quote: I don't understand your statement/question. What are you looking to do? The "acceptable" level of offset would depend upon the available material thickness. Then keep in mind you'll have to make sure you have piston pin boss to rod clearance. I've moved them up to .060". By acceptable I meant before other issues would come into play. But as Jeff posted, it is a non issue. Thank you. TR Waters

Re: Offset Cylinder Boring [Re: DavidDean] #922420 02/06/11 07:46 PM 02/06/11 07:46 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: Good Post Im having to offset the bores of my X block. Im having to shift to the front about .050 to correct wall thickness.There's also some good reading at speedtalk.com. I dont understand... why not just sleeve it I knew if you wanted a big bore they did it but to correct for core shift or a broken cylinder I would have thought just sleeving it would do

Re: Offset Cylinder Boring [Re: MR_P_BODY] #922421 02/06/11 07:55 PM 02/06/11 07:55 PM
Joined: Jul 2009 Posts: 413 Norway (old world) Oyvind Mopar mopar
Oyvind Mopar mopar Joined: Jul 2009 Posts: 413 Norway (old world)	Should not be an issue. The factory did move the c/l of the pistonpin .060 to the side, and some have turned this the other way around, and other pistons do have them in center. So the geometrical difference would be similar to offset boring to the sides. I have salvaged many cylinders by offset boring. My

Re: Offset Cylinder Boring [Re: Oyvind Mopar] #922422 02/06/11 08:35 PM 02/06/11 08:35 PM
Joined: Jan 2003 Posts: 2,129 Vermont T TrWaters OP top fuel
TrWaters OP top fuel T Joined: Jan 2003 Posts: 2,129 Vermont	This particuliar block has good numbers on the outside walls.... drivers minor thrust and passenger major thrust, with fair numbers down the inner walls. Thanks for the replies. TR Waters

Re: Offset Cylinder Boring [Re: MR_P_BODY] #922423 02/07/11 01:39 AM 02/07/11 01:39 AM
Joined: Mar 2003 Posts: 1,632 Lubbock,TX D DavidDean top fuel
DavidDean top fuel D Joined: Mar 2003 Posts: 1,632 Lubbock,TX	Quote: Quote: Good Post Im having to offset the bores of my X block. Im having to shift to the front about .050 to correct wall thickness.There's also some good reading at speedtalk.com. I dont understand... why not just sleeve it I knew if you wanted a big bore they did it but to correct for core shift or a broken cylinder I would have thought just sleeving it would do In my case I would have to sleeve 4 cylinders and this X block hasnt been bored at all

Re: Offset Cylinder Boring [Re: B G Racing] #922424 02/07/11 02:50 AM 02/07/11 02:50 AM
Joined: Jan 2003 Posts: 3,505 DFW M mr_340 master
mr_340 master M Joined: Jan 2003 Posts: 3,505 DFW	Quote: Boring parallel to the centerline of the crankshaft I'm curious to what Bob has found by boring offset to the crank centerline? Does this allow a better push on the piston for more torque? I heard the PS guys were doing it several years back. Any results that can be divulged? Floyd Lippencott IV

Re: Offset Cylinder Boring [Re: mr_340] #922425 02/07/11 06:41 AM 02/07/11 06:41 AM
Joined: Mar 2006 Posts: 9,910 Eighty Four, PA B G Racing master
B G Racing master Joined: Mar 2006 Posts: 9,910 Eighty Four, PA	Quote: Quote: Boring parallel to the centerline of the crankshaft I'm curious to what Bob has found by boring offset to the crank centerline? Does this allow a better push on the piston for more torque? I heard the PS guys were doing it several years back. Any results that can be divulged? It eliminates any odd angle loading(friction)caused by the bore location and allows all pistons and rods to traval in the same plane or designed angle. .Any time you can decrease friction you can gain RPM,HP,TQ. [IMG]http://i430.photobucket.com/albums/qq21/ajcasini/max_zpsdppwd9km.jpg[/IMG]

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