Do I need to bore over 30 to put in pistons? - Page 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**'68OrangeSunshine** · 04-27-2007, 06:09 AM

A 250 L6 @ stock stroke bored .030 over has 254 cubic inches.

**truckdude239** · 04-27-2007, 06:28 AM

the only reason i bored my 305 30 over is because in case it ever gave up the ghost i will be able to bore again

GREASEMONKEY72 · 04-27-2007, 06:44 AM

Quote:

Originally Posted by truckdude239

the only reason i bored my 305 30 over is because in case it ever gave up the ghost i will be able to bore again

thats the exact reason why you shouldnt go the max on the first time out, never know if youll have to bore it again

RustyParts · 04-27-2007, 09:03 AM

Have 'em throw on the torque plates while your at it, makes for nice straight cylinders.

LMN8UR · 04-27-2007, 03:47 PM

Typically blocks are cheaper than good pistons. So if you bore to the max and something fails, you'll have to replace the block and rebore. If something goes wrong and you damage a piston, you'll probably not have a block either.

There are a lot of theories out there. . Start with the machine shop, decide from their.

*Billla* · 04-27-2007, 04:27 PM

Quote:

Originally Posted by Blue71LWB

I'm thinking of putting in some flat top pistons in my inline 250. I feel the engine is fine , but I was told I would need to have it bored if I was going to go with new pistons. I really don't want to bore the block. So will it be OK , to put in new ones without boring ?

Pistons come in different oversizes - .010, .020, .030 and so on. Somtimes there is an .002 or .003 piston as what's called a "high limit" piston - allowing a new piston to be installed after a quick flexi-hone if there's minimal bore wear.

It all starts with a bore measurement - the bore determines what your options are. Once the largest bore size is known, then you know what your options are. Sometimes the inline 6's show little or no bore wear even after 100's of thousands of miles.

**'68OrangeSunshine** · 04-28-2007, 06:26 AM

I've got Badger pistons in my 292. My machinist set me up with them. They are cast pistons. If you want forged pistons you have to go to Arias or Ross, but they're spendy. You might get a line on them at www.inliners.org.
TRW doesn't make them anymore.

PanelDeland · 04-28-2007, 04:17 PM

I would go minimal overbore as suggested.The first thing though is to determine what you can get in the way of pistons without going custom.The options may be limited and could play a part in your decision.Since the 250 hasn't been built in many years there may not be as many choices since the demand has dropped.I also agree on a better cam,the cam reps will be able to help you more on that,make sure to have as many of the specs to give them as possible.Use good qulity head gaskets since the standard compression ratio is about 8.00:1 and the new will be higher.You may also need to run a better grade of fuel(higher octane)since compression will be higher.Since you are going to a 4 barrel you will want a better exhaust also maybe headers or a split manifold.

04-27-2007, 06:09 AM	#1
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,285	Re: Do I need to bore over 30 to put in pistons? A 250 L6 @ stock stroke bored .030 over has 254 cubic inches. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not.

04-27-2007, 06:28 AM	#2
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,234	Re: Do I need to bore over 30 to put in pistons? the only reason i bored my 305 30 over is because in case it ever gave up the ghost i will be able to bore again __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

04-27-2007, 09:03 AM	#4
RustyParts Registered User Join Date: May 2006 Location: Wyman, Kentucky Posts: 403	Re: Do I need to bore over 30 to put in pistons? Have 'em throw on the torque plates while your at it, makes for nice straight cylinders. __________________ 1972 GMC Jimmy, 4WD, 454 CI, 350 Turbo, 4" lift, 35" tires The math teacher said my son "Bubba" could be a mathmatical genius. cause he's got 13 fingers! Last edited by RustyParts; 04-27-2007 at 09:03 AM.

04-27-2007, 03:47 PM	#5
LMN8UR Registered User Join Date: Jun 2005 Location: Midlothian, VA Posts: 148	Re: Do I need to bore over 30 to put in pistons? Typically blocks are cheaper than good pistons. So if you bore to the max and something fails, you'll have to replace the block and rebore. If something goes wrong and you damage a piston, you'll probably not have a block either. There are a lot of theories out there. . Start with the machine shop, decide from their. __________________ 72 Chevy C-10 Custom LWB 383 Stroker - Edlebrock Air Gap intake and 670 CFM Holley Street Avenger carb. Hooker Comp Headers w/ X-Pipe and 2.25 duals TKO-500 & 3.08:1 rear I Love HEMI's, they're soft & chewy!

04-28-2007, 06:26 AM	#7
'68OrangeSunshine Senior Member Join Date: Feb 2002 Location: Tucson, AZ USA Posts: 7,285	Re: Do I need to bore over 30 to put in pistons? I've got Badger pistons in my 292. My machinist set me up with them. They are cast pistons. If you want forged pistons you have to go to Arias or Ross, but they're spendy. You might get a line on them at www.inliners.org. TRW doesn't make them anymore. __________________ Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 04-28-2007 at 06:27 AM.

04-28-2007, 04:17 PM	#8
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Do I need to bore over 30 to put in pistons? I would go minimal overbore as suggested.The first thing though is to determine what you can get in the way of pistons without going custom.The options may be limited and could play a part in your decision.Since the 250 hasn't been built in many years there may not be as many choices since the demand has dropped.I also agree on a better cam,the cam reps will be able to help you more on that,make sure to have as many of the specs to give them as possible.Use good qulity head gaskets since the standard compression ratio is about 8.00:1 and the new will be higher.You may also need to run a better grade of fuel(higher octane)since compression will be higher.Since you are going to a 4 barrel you will want a better exhaust also maybe headers or a split manifold. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" Last edited by PanelDeland; 04-28-2007 at 04:18 PM.



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